[GitHub] [nifi] exceptionfactory commented on a change in pull request #4669: NIFI-7897: Refactored NiFi Stateless to make use of existing NiFi classes

[GitBox <gi...@apache.org>]

exceptionfactory commented on a change in pull request #4669:
URL: https://github.com/apache/nifi/pull/4669#discussion_r524532957



##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-authorization-providers/src/test/java/org/apache/nifi/authorization/CompositeConfigurableUserGroupProviderTest.java
##########
@@ -103,8 +103,8 @@ public void testConfigurableUserGroupProviderOnly() throws Exception {
         });
 
         // users and groups
-        assertEquals(2, userGroupProvider.getUsers().size());
-        assertEquals(1, userGroupProvider.getGroups().size());
+        Assert.assertEquals(2, userGroupProvider.getUsers().size());

Review comment:
       Was there a reason to move away from the static import references for assertEquals?  Otherwise this seems to introduce unnecessary changes in this file and other unit tests.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-components/src/main/java/org/apache/nifi/controller/service/StandardControllerServiceProvider.java
##########
@@ -285,13 +284,20 @@ private void enableControllerServices(final Collection<ControllerServiceNode> se
         }
     }
 
-    private Future<Void> enableControllerServiceDependenciesFirst(ControllerServiceNode serviceNode) {
+    @Override
+    public Future<Void> enableControllerServiceAndDependencies(final ControllerServiceNode serviceNode) {
+        final ControllerServiceState currentState = serviceNode.getState();
+        if (currentState == ControllerServiceState.ENABLED) {
+            logger.debug("Enabling of Controller Service {} triggered but service already eanbled", serviceNode);

Review comment:
       The word **enabled** is not spelled correctly.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-api/src/main/java/org/apache/nifi/stateless/engine/StatelessEngineConfiguration.java
##########
@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.stateless.config.ExtensionClientDefinition;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+
+import java.io.File;
+import java.util.List;
+
+public interface StatelessEngineConfiguration {
+    File getWorkingDirectory();
+
+    File getNarDirectory();
+
+    File getKrb5File();
+
+    SslContextDefinition getSslContext();

Review comment:
       Recommend renaming the method to getSslContextDefinition() since SSLContext is a common class and constructed based on the definition properties.  Is there a reason for creating a new SslContextDefinition class instead of using the TlsConfiguration interface and StandardTlsConfiguration class from nifi-security-utils?  Using those components would avoid creating a different representation of SSL properties particular to stateless NiFi.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-components/src/main/java/org/apache/nifi/reporting/AbstractEventAccess.java
##########
@@ -0,0 +1,687 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.reporting;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.nifi.authorization.resource.Authorizable;
+import org.apache.nifi.components.validation.ValidationStatus;
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.connectable.ConnectableType;
+import org.apache.nifi.connectable.Connection;
+import org.apache.nifi.connectable.Funnel;
+import org.apache.nifi.connectable.Port;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ProcessorNode;
+import org.apache.nifi.controller.ScheduledState;
+import org.apache.nifi.controller.flow.FlowManager;
+import org.apache.nifi.controller.queue.QueueSize;
+import org.apache.nifi.controller.repository.FlowFileEvent;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.repository.RepositoryStatusReport;
+import org.apache.nifi.controller.repository.metrics.EmptyFlowFileEvent;
+import org.apache.nifi.controller.status.ConnectionStatus;
+import org.apache.nifi.controller.status.PortStatus;
+import org.apache.nifi.controller.status.ProcessGroupStatus;
+import org.apache.nifi.controller.status.ProcessorStatus;
+import org.apache.nifi.controller.status.RemoteProcessGroupStatus;
+import org.apache.nifi.controller.status.RunStatus;
+import org.apache.nifi.controller.status.TransmissionStatus;
+import org.apache.nifi.controller.status.analytics.ConnectionStatusPredictions;
+import org.apache.nifi.controller.status.analytics.StatusAnalytics;
+import org.apache.nifi.controller.status.analytics.StatusAnalyticsEngine;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.groups.RemoteProcessGroup;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.provenance.ProvenanceEventRecord;
+import org.apache.nifi.registry.flow.VersionControlInformation;
+import org.apache.nifi.registry.flow.VersionedFlowState;
+import org.apache.nifi.registry.flow.VersionedFlowStatus;
+import org.apache.nifi.remote.PublicPort;
+import org.apache.nifi.remote.RemoteGroupPort;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Predicate;
+
+public abstract class AbstractEventAccess implements EventAccess {
+    private static final Logger logger = LoggerFactory.getLogger(AbstractEventAccess.class);
+
+    private final ProcessScheduler processScheduler;
+    private final StatusAnalyticsEngine statusAnalyticsEngine;
+    private final FlowManager flowManager;
+    private final FlowFileEventRepository flowFileEventRepository;
+
+    public AbstractEventAccess(final ProcessScheduler processScheduler, final StatusAnalyticsEngine analyticsEngine, final FlowManager flowManager,
+                               final FlowFileEventRepository flowFileEventRepository) {
+        this.processScheduler = processScheduler;
+        this.statusAnalyticsEngine = analyticsEngine;
+        this.flowManager = flowManager;
+        this.flowFileEventRepository = flowFileEventRepository;
+    }
+
+    /**
+     * Returns the status of all components in the specified group. This request
+     * is not in the context of a user so the results will be unfiltered.
+     *
+     * @param groupId group id
+     * @return the component status
+     */
+    @Override
+    public ProcessGroupStatus getGroupStatus(final String groupId) {
+        final RepositoryStatusReport repoStatusReport = generateRepositoryStatusReport();
+        return getGroupStatus(groupId, repoStatusReport);
+    }
+
+    /**
+     * Returns the status for the components in the specified group with the
+     * specified report. This request is not in the context of a user so the
+     * results will be unfiltered.
+     *
+     * @param groupId group id
+     * @param statusReport report
+     * @return the component status
+     */
+    public ProcessGroupStatus getGroupStatus(final String groupId, final RepositoryStatusReport statusReport) {
+        final ProcessGroup group = flowManager.getGroup(groupId);
+
+        // this was invoked with no user context so the results will be unfiltered... necessary for aggregating status history
+        return getGroupStatus(group, statusReport, authorizable -> true, Integer.MAX_VALUE, 1);
+    }
+
+    protected RepositoryStatusReport generateRepositoryStatusReport() {
+        return flowFileEventRepository.reportTransferEvents(System.currentTimeMillis());
+    }
+
+
+    /**
+     * Returns the status for the components in the specified group with the
+     * specified report. The results will be filtered by executing the specified
+     * predicate.
+     *
+     * @param group group id
+     * @param statusReport report
+     * @param isAuthorized is authorized check
+     * @param recursiveStatusDepth the number of levels deep we should recurse and still include the the processors' statuses, the groups' statuses, etc. in the returned ProcessGroupStatus
+     * @param currentDepth the current number of levels deep that we have recursed
+     * @return the component status
+     */
+    ProcessGroupStatus getGroupStatus(final ProcessGroup group, final RepositoryStatusReport statusReport, final Predicate<Authorizable> isAuthorized,
+                                      final int recursiveStatusDepth, final int currentDepth) {
+        if (group == null) {
+            return null;
+        }
+
+        final ProcessGroupStatus status = new ProcessGroupStatus();
+        status.setId(group.getIdentifier());
+        status.setName(isAuthorized.test(group) ? group.getName() : group.getIdentifier());
+        int activeGroupThreads = 0;
+        int terminatedGroupThreads = 0;
+        long bytesRead = 0L;
+        long bytesWritten = 0L;
+        int queuedCount = 0;
+        long queuedContentSize = 0L;
+        int flowFilesIn = 0;
+        long bytesIn = 0L;
+        int flowFilesOut = 0;
+        long bytesOut = 0L;
+        int flowFilesReceived = 0;
+        long bytesReceived = 0L;
+        int flowFilesSent = 0;
+        long bytesSent = 0L;
+        int flowFilesTransferred = 0;
+        long bytesTransferred = 0;
+
+        final boolean populateChildStatuses = currentDepth <= recursiveStatusDepth;
+
+        // set status for processors
+        final Collection<ProcessorStatus> processorStatusCollection = new ArrayList<>();
+        status.setProcessorStatus(processorStatusCollection);
+        for (final ProcessorNode procNode : group.getProcessors()) {
+            final ProcessorStatus procStat = getProcessorStatus(statusReport, procNode, isAuthorized);
+            if (populateChildStatuses) {
+                processorStatusCollection.add(procStat);
+            }
+            activeGroupThreads += procStat.getActiveThreadCount();
+            terminatedGroupThreads += procStat.getTerminatedThreadCount();
+            bytesRead += procStat.getBytesRead();
+            bytesWritten += procStat.getBytesWritten();
+
+            flowFilesReceived += procStat.getFlowFilesReceived();
+            bytesReceived += procStat.getBytesReceived();
+            flowFilesSent += procStat.getFlowFilesSent();
+            bytesSent += procStat.getBytesSent();
+        }
+
+        // set status for local child groups
+        final Collection<ProcessGroupStatus> localChildGroupStatusCollection = new ArrayList<>();
+        status.setProcessGroupStatus(localChildGroupStatusCollection);
+        for (final ProcessGroup childGroup : group.getProcessGroups()) {
+            final ProcessGroupStatus childGroupStatus;
+            if (populateChildStatuses) {
+                childGroupStatus = getGroupStatus(childGroup, statusReport, isAuthorized, recursiveStatusDepth, currentDepth + 1);
+                localChildGroupStatusCollection.add(childGroupStatus);
+            } else {
+                // In this case, we don't want to include any of the recursive components' individual statuses. As a result, we can
+                // avoid performing any sort of authorizations. Because we only care about the numbers that come back, we can just indicate
+                // that the user is not authorized. This allows us to avoid the expense of both performing the authorization and calculating
+                // things that we would otherwise need to calculate if the user were in fact authorized.
+                childGroupStatus = getGroupStatus(childGroup, statusReport, authorizable -> false, recursiveStatusDepth, currentDepth + 1);
+            }
+
+            activeGroupThreads += childGroupStatus.getActiveThreadCount();
+            terminatedGroupThreads += childGroupStatus.getTerminatedThreadCount();
+            bytesRead += childGroupStatus.getBytesRead();
+            bytesWritten += childGroupStatus.getBytesWritten();
+            queuedCount += childGroupStatus.getQueuedCount();
+            queuedContentSize += childGroupStatus.getQueuedContentSize();
+
+            flowFilesReceived += childGroupStatus.getFlowFilesReceived();
+            bytesReceived += childGroupStatus.getBytesReceived();
+            flowFilesSent += childGroupStatus.getFlowFilesSent();
+            bytesSent += childGroupStatus.getBytesSent();
+
+            flowFilesTransferred += childGroupStatus.getFlowFilesTransferred();
+            bytesTransferred += childGroupStatus.getBytesTransferred();
+        }
+
+        // set status for remote child groups
+        final Collection<RemoteProcessGroupStatus> remoteProcessGroupStatusCollection = new ArrayList<>();
+        status.setRemoteProcessGroupStatus(remoteProcessGroupStatusCollection);
+        for (final RemoteProcessGroup remoteGroup : group.getRemoteProcessGroups()) {
+            final RemoteProcessGroupStatus remoteStatus = createRemoteGroupStatus(remoteGroup, statusReport, isAuthorized);
+            if (remoteStatus != null) {
+                if (populateChildStatuses) {
+                    remoteProcessGroupStatusCollection.add(remoteStatus);
+                }
+
+                flowFilesReceived += remoteStatus.getReceivedCount();
+                bytesReceived += remoteStatus.getReceivedContentSize();
+                flowFilesSent += remoteStatus.getSentCount();
+                bytesSent += remoteStatus.getSentContentSize();
+            }
+        }
+
+        // connection status
+        final Collection<ConnectionStatus> connectionStatusCollection = new ArrayList<>();
+        status.setConnectionStatus(connectionStatusCollection);
+
+        // get the connection and remote port status
+        for (final Connection conn : group.getConnections()) {
+            final boolean isConnectionAuthorized = isAuthorized.test(conn);
+            final boolean isSourceAuthorized = isAuthorized.test(conn.getSource());
+            final boolean isDestinationAuthorized = isAuthorized.test(conn.getDestination());
+
+            final ConnectionStatus connStatus = new ConnectionStatus();
+            connStatus.setId(conn.getIdentifier());
+            connStatus.setGroupId(conn.getProcessGroup().getIdentifier());
+            connStatus.setSourceId(conn.getSource().getIdentifier());
+            connStatus.setSourceName(isSourceAuthorized ? conn.getSource().getName() : conn.getSource().getIdentifier());
+            connStatus.setDestinationId(conn.getDestination().getIdentifier());
+            connStatus.setDestinationName(isDestinationAuthorized ? conn.getDestination().getName() : conn.getDestination().getIdentifier());
+            connStatus.setBackPressureDataSizeThreshold(conn.getFlowFileQueue().getBackPressureDataSizeThreshold());
+            connStatus.setBackPressureObjectThreshold(conn.getFlowFileQueue().getBackPressureObjectThreshold());
+
+            final FlowFileEvent connectionStatusReport = statusReport.getReportEntry(conn.getIdentifier());
+            if (connectionStatusReport != null) {
+                connStatus.setInputBytes(connectionStatusReport.getContentSizeIn());
+                connStatus.setInputCount(connectionStatusReport.getFlowFilesIn());
+                connStatus.setOutputBytes(connectionStatusReport.getContentSizeOut());
+                connStatus.setOutputCount(connectionStatusReport.getFlowFilesOut());
+
+                flowFilesTransferred += connectionStatusReport.getFlowFilesIn() + connectionStatusReport.getFlowFilesOut();
+                bytesTransferred += connectionStatusReport.getContentSizeIn() + connectionStatusReport.getContentSizeOut();
+            }
+
+            if (statusAnalyticsEngine != null) {
+                StatusAnalytics statusAnalytics =  statusAnalyticsEngine.getStatusAnalytics(conn.getIdentifier());
+                if (statusAnalytics != null) {
+                    Map<String,Long> predictionValues = statusAnalytics.getPredictions();
+                    ConnectionStatusPredictions predictions = new ConnectionStatusPredictions();
+                    connStatus.setPredictions(predictions);
+                    predictions.setPredictedTimeToBytesBackpressureMillis(predictionValues.get("timeToBytesBackpressureMillis"));
+                    predictions.setPredictedTimeToCountBackpressureMillis(predictionValues.get("timeToCountBackpressureMillis"));
+                    predictions.setNextPredictedQueuedBytes(predictionValues.get("nextIntervalBytes"));
+                    predictions.setNextPredictedQueuedCount(predictionValues.get("nextIntervalCount").intValue());
+                    predictions.setPredictedPercentCount(predictionValues.get("nextIntervalPercentageUseCount").intValue());
+                    predictions.setPredictedPercentBytes(predictionValues.get("nextIntervalPercentageUseBytes").intValue());
+                    predictions.setPredictionIntervalMillis(predictionValues.get("intervalTimeMillis"));
+                }
+            } else {
+                connStatus.setPredictions(null);
+            }
+
+            if (isConnectionAuthorized) {
+                if (StringUtils.isNotBlank(conn.getName())) {
+                    connStatus.setName(conn.getName());
+                } else if (conn.getRelationships() != null && !conn.getRelationships().isEmpty()) {
+                    final Collection<String> relationships = new ArrayList<>(conn.getRelationships().size());
+                    for (final Relationship relationship : conn.getRelationships()) {
+                        relationships.add(relationship.getName());
+                    }
+                    connStatus.setName(StringUtils.join(relationships, ", "));
+                }
+            } else {
+                connStatus.setName(conn.getIdentifier());
+            }
+
+            final QueueSize queueSize = conn.getFlowFileQueue().size();
+            final int connectionQueuedCount = queueSize.getObjectCount();
+            final long connectionQueuedBytes = queueSize.getByteCount();
+            if (connectionQueuedCount > 0) {
+                connStatus.setQueuedBytes(connectionQueuedBytes);
+                connStatus.setQueuedCount(connectionQueuedCount);
+            }
+
+            if (populateChildStatuses) {
+                connectionStatusCollection.add(connStatus);
+            }
+
+            queuedCount += connectionQueuedCount;
+            queuedContentSize += connectionQueuedBytes;
+
+            final Connectable source = conn.getSource();
+            if (ConnectableType.REMOTE_OUTPUT_PORT.equals(source.getConnectableType())) {
+                final RemoteGroupPort remoteOutputPort = (RemoteGroupPort) source;
+                activeGroupThreads += processScheduler.getActiveThreadCount(remoteOutputPort);
+            }
+
+            final Connectable destination = conn.getDestination();
+            if (ConnectableType.REMOTE_INPUT_PORT.equals(destination.getConnectableType())) {
+                final RemoteGroupPort remoteInputPort = (RemoteGroupPort) destination;
+                activeGroupThreads += processScheduler.getActiveThreadCount(remoteInputPort);
+            }
+        }
+
+        // status for input ports
+        final Collection<PortStatus> inputPortStatusCollection = new ArrayList<>();
+        status.setInputPortStatus(inputPortStatusCollection);
+
+        final Set<Port> inputPorts = group.getInputPorts();
+        for (final Port port : inputPorts) {
+            final boolean isInputPortAuthorized = isAuthorized.test(port);
+
+            final PortStatus portStatus = new PortStatus();
+            portStatus.setId(port.getIdentifier());
+            portStatus.setGroupId(port.getProcessGroup().getIdentifier());
+            portStatus.setName(isInputPortAuthorized ? port.getName() : port.getIdentifier());
+            portStatus.setActiveThreadCount(processScheduler.getActiveThreadCount(port));
+
+            // determine the run status
+            if (ScheduledState.RUNNING.equals(port.getScheduledState())) {
+                portStatus.setRunStatus(RunStatus.Running);
+            } else if (ScheduledState.DISABLED.equals(port.getScheduledState())) {
+                portStatus.setRunStatus(RunStatus.Disabled);
+            } else if (!port.isValid()) {
+                portStatus.setRunStatus(RunStatus.Invalid);
+            } else {
+                portStatus.setRunStatus(RunStatus.Stopped);
+            }
+
+            // special handling for public ports
+            if (port instanceof PublicPort) {
+                portStatus.setTransmitting(((PublicPort) port).isTransmitting());
+            }
+
+            final FlowFileEvent entry = statusReport.getReportEntries().get(port.getIdentifier());
+            if (entry == null) {
+                portStatus.setInputBytes(0L);
+                portStatus.setInputCount(0);
+                portStatus.setOutputBytes(0L);
+                portStatus.setOutputCount(0);
+            } else {
+                final int processedCount = entry.getFlowFilesOut();
+                final long numProcessedBytes = entry.getContentSizeOut();
+                portStatus.setOutputBytes(numProcessedBytes);
+                portStatus.setOutputCount(processedCount);
+
+                final int inputCount = entry.getFlowFilesIn();
+                final long inputBytes = entry.getContentSizeIn();
+                portStatus.setInputBytes(inputBytes);
+                portStatus.setInputCount(inputCount);
+
+                flowFilesIn += port instanceof PublicPort ? entry.getFlowFilesReceived() : inputCount;
+                bytesIn += port instanceof PublicPort ? entry.getBytesReceived() : inputBytes;
+
+                bytesWritten += entry.getBytesWritten();
+
+                flowFilesReceived += entry.getFlowFilesReceived();
+                bytesReceived += entry.getBytesReceived();
+            }
+
+            if (populateChildStatuses) {
+                inputPortStatusCollection.add(portStatus);
+            }
+
+            activeGroupThreads += portStatus.getActiveThreadCount();
+        }
+
+        // status for output ports
+        final Collection<PortStatus> outputPortStatusCollection = new ArrayList<>();
+        status.setOutputPortStatus(outputPortStatusCollection);
+
+        final Set<Port> outputPorts = group.getOutputPorts();
+        for (final Port port : outputPorts) {
+            final boolean isOutputPortAuthorized = isAuthorized.test(port);
+
+            final PortStatus portStatus = new PortStatus();
+            portStatus.setId(port.getIdentifier());
+            portStatus.setGroupId(port.getProcessGroup().getIdentifier());
+            portStatus.setName(isOutputPortAuthorized ? port.getName() : port.getIdentifier());
+            portStatus.setActiveThreadCount(processScheduler.getActiveThreadCount(port));
+
+            // determine the run status
+            if (ScheduledState.RUNNING.equals(port.getScheduledState())) {
+                portStatus.setRunStatus(RunStatus.Running);
+            } else if (ScheduledState.DISABLED.equals(port.getScheduledState())) {
+                portStatus.setRunStatus(RunStatus.Disabled);
+            } else if (!port.isValid()) {
+                portStatus.setRunStatus(RunStatus.Invalid);
+            } else {
+                portStatus.setRunStatus(RunStatus.Stopped);
+            }
+
+            // special handling for public ports
+            if (port instanceof PublicPort) {
+                portStatus.setTransmitting(((PublicPort) port).isTransmitting());
+            }
+
+            final FlowFileEvent entry = statusReport.getReportEntries().get(port.getIdentifier());
+            if (entry == null) {
+                portStatus.setInputBytes(0L);
+                portStatus.setInputCount(0);
+                portStatus.setOutputBytes(0L);
+                portStatus.setOutputCount(0);
+            } else {
+                final int processedCount = entry.getFlowFilesOut();
+                final long numProcessedBytes = entry.getContentSizeOut();
+                portStatus.setOutputBytes(numProcessedBytes);
+                portStatus.setOutputCount(processedCount);
+
+                final int inputCount = entry.getFlowFilesIn();
+                final long inputBytes = entry.getContentSizeIn();
+                portStatus.setInputBytes(inputBytes);
+                portStatus.setInputCount(inputCount);
+
+                bytesRead += entry.getBytesRead();
+
+                flowFilesOut += port instanceof PublicPort ? entry.getFlowFilesSent() : entry.getFlowFilesOut();
+                bytesOut += port instanceof PublicPort ? entry.getBytesSent() : entry.getContentSizeOut();
+
+                flowFilesSent = entry.getFlowFilesSent();
+                bytesSent += entry.getBytesSent();
+            }
+
+            if (populateChildStatuses) {
+                outputPortStatusCollection.add(portStatus);
+            }
+
+            activeGroupThreads += portStatus.getActiveThreadCount();
+        }
+
+        for (final Funnel funnel : group.getFunnels()) {
+            activeGroupThreads += processScheduler.getActiveThreadCount(funnel);
+        }
+
+        status.setActiveThreadCount(activeGroupThreads);
+        status.setTerminatedThreadCount(terminatedGroupThreads);
+        status.setBytesRead(bytesRead);
+        status.setBytesWritten(bytesWritten);
+        status.setQueuedCount(queuedCount);
+        status.setQueuedContentSize(queuedContentSize);
+        status.setInputContentSize(bytesIn);
+        status.setInputCount(flowFilesIn);
+        status.setOutputContentSize(bytesOut);
+        status.setOutputCount(flowFilesOut);
+        status.setFlowFilesReceived(flowFilesReceived);
+        status.setBytesReceived(bytesReceived);
+        status.setFlowFilesSent(flowFilesSent);
+        status.setBytesSent(bytesSent);
+        status.setFlowFilesTransferred(flowFilesTransferred);
+        status.setBytesTransferred(bytesTransferred);
+
+        final VersionControlInformation vci = group.getVersionControlInformation();
+        if (vci != null) {
+            try {
+                final VersionedFlowStatus flowStatus = vci.getStatus();
+                if (flowStatus != null && flowStatus.getState() != null) {
+                    status.setVersionedFlowState(flowStatus.getState());
+                }
+            } catch (final Exception e) {
+                logger.warn("Failed to determine Version Control State for {}. Will consider state to be SYNC_FAILURE", group, e);
+                status.setVersionedFlowState(VersionedFlowState.SYNC_FAILURE);
+            }
+        }
+
+        return status;
+    }
+
+    private RemoteProcessGroupStatus createRemoteGroupStatus(final RemoteProcessGroup remoteGroup, final RepositoryStatusReport statusReport, final Predicate<Authorizable> isAuthorized) {
+        final boolean isRemoteProcessGroupAuthorized = isAuthorized.test(remoteGroup);
+
+        int receivedCount = 0;
+        long receivedContentSize = 0L;
+        int sentCount = 0;
+        long sentContentSize = 0L;
+        int activeThreadCount = 0;
+        int activePortCount = 0;
+        int inactivePortCount = 0;
+
+        final RemoteProcessGroupStatus status = new RemoteProcessGroupStatus();
+        status.setGroupId(remoteGroup.getProcessGroup().getIdentifier());
+        status.setName(isRemoteProcessGroupAuthorized ? remoteGroup.getName() : remoteGroup.getIdentifier());
+        status.setTargetUri(isRemoteProcessGroupAuthorized ? remoteGroup.getTargetUri() : null);
+
+        long lineageMillis = 0L;
+        int flowFilesRemoved = 0;
+        int flowFilesTransferred = 0;
+        for (final Port port : remoteGroup.getInputPorts()) {
+            // determine if this input port is connected
+            final boolean isConnected = port.hasIncomingConnection();
+
+            // we only want to consider remote ports that we are connected to
+            if (isConnected) {
+                if (port.isRunning()) {
+                    activePortCount++;
+                } else {
+                    inactivePortCount++;
+                }
+
+                activeThreadCount += processScheduler.getActiveThreadCount(port);
+
+                final FlowFileEvent portEvent = statusReport.getReportEntry(port.getIdentifier());
+                if (portEvent != null) {
+                    lineageMillis += portEvent.getAggregateLineageMillis();
+                    flowFilesRemoved += portEvent.getFlowFilesRemoved();
+                    flowFilesTransferred += portEvent.getFlowFilesOut();
+                    sentCount += portEvent.getFlowFilesSent();
+                    sentContentSize += portEvent.getBytesSent();
+                }
+            }
+        }
+
+        for (final Port port : remoteGroup.getOutputPorts()) {
+            // determine if this output port is connected
+            final boolean isConnected = !port.getConnections().isEmpty();
+
+            // we only want to consider remote ports that we are connected from
+            if (isConnected) {
+                if (port.isRunning()) {
+                    activePortCount++;
+                } else {
+                    inactivePortCount++;
+                }
+
+                activeThreadCount += processScheduler.getActiveThreadCount(port);
+
+                final FlowFileEvent portEvent = statusReport.getReportEntry(port.getIdentifier());
+                if (portEvent != null) {
+                    receivedCount += portEvent.getFlowFilesReceived();
+                    receivedContentSize += portEvent.getBytesReceived();
+                }
+            }
+        }
+
+        status.setId(remoteGroup.getIdentifier());
+        status.setTransmissionStatus(remoteGroup.isTransmitting() ? TransmissionStatus.Transmitting : TransmissionStatus.NotTransmitting);
+        status.setActiveThreadCount(activeThreadCount);
+        status.setReceivedContentSize(receivedContentSize);
+        status.setReceivedCount(receivedCount);
+        status.setSentContentSize(sentContentSize);
+        status.setSentCount(sentCount);
+        status.setActiveRemotePortCount(activePortCount);
+        status.setInactiveRemotePortCount(inactivePortCount);
+
+        final int flowFilesOutOrRemoved = flowFilesTransferred + flowFilesRemoved;
+        status.setAverageLineageDuration(flowFilesOutOrRemoved == 0 ? 0 : lineageMillis / flowFilesOutOrRemoved, TimeUnit.MILLISECONDS);
+
+        return status;
+    }
+
+    private ProcessorStatus getProcessorStatus(final RepositoryStatusReport report, final ProcessorNode procNode, final Predicate<Authorizable> isAuthorized) {
+        final FlowFileEvent entry = report.getReportEntries().get(procNode.getIdentifier());
+        return getProcessorStatus(entry, procNode, isAuthorized);
+    }
+
+    protected ProcessorStatus getProcessorStatus(final FlowFileEvent flowFileEvent, final ProcessorNode procNode, final Predicate<Authorizable> isAuthorized) {
+        final boolean isProcessorAuthorized = isAuthorized.test(procNode);
+
+        final ProcessorStatus status = new ProcessorStatus();
+        status.setId(procNode.getIdentifier());
+        status.setGroupId(procNode.getProcessGroup().getIdentifier());
+        status.setName(isProcessorAuthorized ? procNode.getName() : procNode.getIdentifier());
+        status.setType(isProcessorAuthorized ? procNode.getComponentType() : "Processor");

Review comment:
       For implementation clarity, would it be worth creating a static String named UNAUTHORIZED_COMPONENT_TYPE to use here as the fallback value?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/config/PropertiesFileFlowDefinitionParser.java
##########
@@ -0,0 +1,335 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.config;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.nifi.registry.client.NiFiRegistryException;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshotMetadata;
+import org.apache.nifi.stateless.core.RegistryUtil;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.flow.DataflowDefinition;
+import org.apache.nifi.stateless.flow.DataflowDefinitionParser;
+import org.apache.nifi.stateless.flow.StandardDataflowDefinition;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class PropertiesFileFlowDefinitionParser implements DataflowDefinitionParser {
+    private static final Logger logger = LoggerFactory.getLogger(PropertiesFileFlowDefinitionParser.class);
+    private static final Pattern PROPERTY_LINE_PATTERN = Pattern.compile("(.*?)(?<!\\\\)=(.*)");
+    // parameter context pattern starts with "nifi.stateless.parameters." followed by the name of a parameter context.
+    // After the name of the parameter context, it may or may not have a ".<parameter name>" component, then an equals (=) and a value.
+    private static final Pattern PARAMETER_CONTEXT_PATTERN = Pattern.compile("\\Qnifi.stateless.parameters.\\E(.*?)(\\..*)?");
+    private static final Pattern REPORTING_TASK_PATTERN = Pattern.compile("\\Qnifi.stateless.reporting.task.\\E(.*?)\\.(.*)");
+
+    // Property names/keys
+    private static final String FAILURE_PORTS_KEY = "nifi.stateless.failure.port.names";
+    private static final String REGISTRY_URL_KEY = "nifi.stateless.registry.url";
+    private static final String BUCKET_ID_KEY = "nifi.stateless.flow.bucketId";
+    private static final String FLOW_ID_KEY = "nifi.stateless.flow.id";
+    private static final String FLOW_VERSION_KEY = "nifi.stateless.flow.version";
+    private static final String FLOW_SNAPSHOT_FILE_KEY = "nifi.stateless.flow.snapshot.file";
+
+
+    public DataflowDefinition<VersionedFlowSnapshot> parseFlowDefinition(final File propertiesFile, final StatelessEngineConfiguration engineConfig)
+                throws IOException, StatelessConfigurationException {
+
+        final Map<String, String> properties = readPropertyValues(propertiesFile);
+
+        // A common problem is users accidentally including whitespace at the beginning or end of property values.
+        // We can't just blindly trim the white space because it may be relevant. For example, there may be a Parameter
+        // that has a value of a literal space ( ), such as a character for a delimiter, and we don't want to remove
+        // that and result in an empty string. So we will log a warning that it may be a problem.
+        warnOnWhitespace(properties, propertiesFile.getAbsolutePath());
+
+        final Set<String> failurePortNames = getFailurePortNames(properties);
+        final SSLContext sslContext = SslConfigurationUtil.createSslContext(engineConfig.getSslContext());
+        final VersionedFlowSnapshot flowSnapshot = fetchVersionedFlowSnapshot(properties, propertiesFile, sslContext);
+        final List<ParameterContextDefinition> parameterContextDefinitions = getParameterContexts(properties);
+        final List<ReportingTaskDefinition> reportingTaskDefinitions = getReportingTasks(properties);
+
+        return new StandardDataflowDefinition.Builder()
+            .flowSnapshot(flowSnapshot)
+            .failurePortNames(failurePortNames)
+            .parameterContexts(parameterContextDefinitions)
+            .reportingTasks(reportingTaskDefinitions)
+            .build();
+    }
+
+    private List<ReportingTaskDefinition> getReportingTasks(final Map<String, String> properties) {
+        final Map<String, ReportingTaskDefinition> reportingTaskDefinitions = new LinkedHashMap<>();
+
+        for (final String propertyName : properties.keySet()) {
+            final Matcher matcher = REPORTING_TASK_PATTERN.matcher(propertyName);
+            if (!matcher.matches()) {
+                continue;
+            }
+
+            // For a property name like:
+            // nifi.stateless.reporting.task.abc.name=hello
+            // We consider 'abc' the <reporting task key> and 'name' the <relative property name>
+            final String reportingTaskKey = matcher.group(1);
+            final ReportingTaskDefinition definition = reportingTaskDefinitions.computeIfAbsent(reportingTaskKey, key -> new ReportingTaskDefinition());
+            final String relativePropertyName = matcher.group(2);
+            final String propertyValue = properties.get(propertyName);
+
+            if (relativePropertyName.startsWith("properties.")) {
+                if (relativePropertyName.length() < 12) {

Review comment:
       The reason for the length check against 12 is not immediately apparent, declaring a static String for properties prefix and properties prefix length would help make this check more intuitive.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/StatelessFlowManager.java
##########
@@ -0,0 +1,365 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.annotation.lifecycle.OnAdded;
+import org.apache.nifi.annotation.lifecycle.OnConfigurationRestored;
+import org.apache.nifi.authorization.resource.Authorizable;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.connectable.ConnectableType;
+import org.apache.nifi.connectable.Connection;
+import org.apache.nifi.connectable.Funnel;
+import org.apache.nifi.connectable.LocalPort;
+import org.apache.nifi.connectable.Port;
+import org.apache.nifi.connectable.StandardConnection;
+import org.apache.nifi.controller.ControllerService;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ProcessorNode;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.StandardFunnel;
+import org.apache.nifi.controller.StandardProcessorNode;
+import org.apache.nifi.controller.exception.ComponentLifeCycleException;
+import org.apache.nifi.controller.exception.ProcessorInstantiationException;
+import org.apache.nifi.controller.flow.AbstractFlowManager;
+import org.apache.nifi.controller.flow.FlowManager;
+import org.apache.nifi.controller.label.Label;
+import org.apache.nifi.controller.label.StandardLabel;
+import org.apache.nifi.controller.queue.ConnectionEventListener;
+import org.apache.nifi.controller.queue.FlowFileQueue;
+import org.apache.nifi.controller.queue.FlowFileQueueFactory;
+import org.apache.nifi.controller.queue.LoadBalanceStrategy;
+import org.apache.nifi.controller.reporting.ReportingTaskInstantiationException;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceNode;
+import org.apache.nifi.flowfile.FlowFilePrioritizer;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.groups.RemoteProcessGroup;
+import org.apache.nifi.groups.StandardProcessGroup;
+import org.apache.nifi.logging.LogRepository;
+import org.apache.nifi.logging.LogRepositoryFactory;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.nar.NarCloseable;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.registry.variable.MutableVariableRegistry;
+import org.apache.nifi.remote.StandardRemoteProcessGroup;
+import org.apache.nifi.stateless.queue.StatelessFlowFileQueue;
+import org.apache.nifi.util.ReflectionUtils;
+import org.apache.nifi.web.api.dto.FlowSnippetDTO;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.function.BooleanSupplier;
+
+import static java.util.Objects.requireNonNull;
+
+public class StatelessFlowManager extends AbstractFlowManager implements FlowManager {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessFlowManager.class);
+
+    private final StatelessEngine<VersionedFlowSnapshot> statelessEngine;
+    private final SSLContext sslContext;
+
+    public StatelessFlowManager(final FlowFileEventRepository flowFileEventRepository, final ParameterContextManager parameterContextManager,
+                                final StatelessEngine<VersionedFlowSnapshot> statelessEngine, final BooleanSupplier flowInitializedCheck,
+                                final SSLContext sslContext) {
+        super(flowFileEventRepository, parameterContextManager, statelessEngine.getFlowRegistryClient(), flowInitializedCheck);
+
+        this.statelessEngine = statelessEngine;
+        this.sslContext = sslContext;
+    }
+
+    @Override
+    public Port createPublicInputPort(final String id, final String name) {
+        throw new UnsupportedOperationException("Create create Public Input Port with name '" + name + "' because Public Input Ports and Public Output Ports are not supported in Stateless NiFi");
+    }
+
+    @Override
+    public Port createPublicOutputPort(final String id, final String name) {
+        throw new UnsupportedOperationException("Create create Public Input Port with name '" + name + "' because Public Input Ports and Public Output Ports are not supported in Stateless NiFi");

Review comment:
       The message should be adjusted to indicate "Public Output Port" instead of "Public Input Port" and the word "create" should not be repeated.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/test/java/org/apache/nifi/stateless/config/TestPropertiesFileFlowDefinitionParser.java
##########
@@ -0,0 +1,98 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.config;
+
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.flow.DataflowDefinition;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class TestPropertiesFileFlowDefinitionParser {
+
+    @Test
+    public void testParse() throws IOException, StatelessConfigurationException {
+        final PropertiesFileFlowDefinitionParser parser = new PropertiesFileFlowDefinitionParser();
+
+        final DataflowDefinition dataflowDefinition = parser.parseFlowDefinition(new File("src/test/resources/flow-configuration.properties"), createStatelessEngineConfiguration());

Review comment:
       Recommend changing the File path reference to use getClass().getResource("/flow-configuration.properties") to avoid having to reference the "src/test/resources" path.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/StatelessProcessScheduler.java
##########
@@ -0,0 +1,285 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.components.validation.ValidationStatus;
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.connectable.Funnel;
+import org.apache.nifi.connectable.Port;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ProcessorNode;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.SchedulingAgentCallback;
+import org.apache.nifi.controller.scheduling.LifecycleState;
+import org.apache.nifi.controller.scheduling.SchedulingAgent;
+import org.apache.nifi.controller.service.ControllerServiceNode;
+import org.apache.nifi.engine.FlowEngine;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.nar.NarCloseable;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.reporting.ReportingTask;
+import org.apache.nifi.scheduling.SchedulingStrategy;
+import org.apache.nifi.util.ReflectionUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+/**
+ * A ProcessScheduler that handles the lifecycle management of components but does not
+ * schedule the triggering of components.
+ */
+public class StatelessProcessScheduler implements ProcessScheduler {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessProcessScheduler.class);
+    private static final int ADMINISTRATIVE_YIELD_MILLIS = 1000;
+
+    private final SchedulingAgent schedulingAgent;
+    private final ExtensionManager extensionManager;
+
+    private FlowEngine componentLifeCycleThreadPool;
+    private ScheduledExecutorService componentMonitoringThreadPool;
+    private ProcessContextFactory processContextFactory;
+
+    public StatelessProcessScheduler(final ExtensionManager extensionManager) {
+        this.extensionManager = extensionManager;
+        schedulingAgent = new StatelessSchedulingAgent(extensionManager);
+    }
+
+    @Override
+    public void shutdown() {
+        if (componentLifeCycleThreadPool != null) {
+            componentLifeCycleThreadPool.shutdown();
+        }
+
+        if (componentMonitoringThreadPool != null) {
+            componentMonitoringThreadPool.shutdown();
+        }
+    }
+
+    public void initialize(final ProcessContextFactory processContextFactory) {
+        this.processContextFactory = processContextFactory;
+
+        componentLifeCycleThreadPool = new FlowEngine(8, "Component Lifecycle");
+        componentMonitoringThreadPool = new FlowEngine(2, "Monitor Processor Lifecycle", true);
+    }
+
+    @Override
+    public Future<Void> startProcessor(final ProcessorNode procNode, final boolean failIfStopping) {
+        final CompletableFuture<Void> future = new CompletableFuture<>();
+        final SchedulingAgentCallback callback = new SchedulingAgentCallback() {
+            @Override
+            public void trigger() {
+                // Initialization / scheduling has completed.
+                future.complete(null);
+            }
+
+            @Override
+            public Future<?> scheduleTask(final Callable<?> task) {
+                return componentLifeCycleThreadPool.submit(task);
+            }
+
+            @Override
+            public void onTaskComplete() {
+            }
+        };
+
+        logger.info("Starting {}", procNode);
+
+        final Supplier<ProcessContext> processContextSupplier = () -> processContextFactory.createProcessContext(procNode);
+        procNode.start(componentMonitoringThreadPool, 1000L, 10_000L, processContextSupplier, callback, failIfStopping);

Review comment:
       Recommend declaring static final variables for 1000L and 10_000L since ADMINISTRATIVE_YIELD_MILLIS follows that patterns and makes the intended usage of these numbers more explicit.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/StandardStatelessEngine.java
##########
@@ -0,0 +1,550 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.bundle.Bundle;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.components.AllowableValue;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.validation.StandardValidationTrigger;
+import org.apache.nifi.components.validation.ValidationTrigger;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ReloadComponent;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.flow.FlowManager;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.encrypt.StringEncryptor;
+import org.apache.nifi.engine.FlowEngine;
+import org.apache.nifi.extensions.ExtensionRepository;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.parameter.Parameter;
+import org.apache.nifi.parameter.ParameterContext;
+import org.apache.nifi.provenance.ProvenanceRepository;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.FlowRegistryClient;
+import org.apache.nifi.registry.flow.VersionedFlow;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.registry.flow.VersionedProcessGroup;
+import org.apache.nifi.reporting.BulletinRepository;
+import org.apache.nifi.reporting.ReportingTask;
+import org.apache.nifi.scheduling.SchedulingStrategy;
+import org.apache.nifi.stateless.config.ParameterContextDefinition;
+import org.apache.nifi.stateless.config.ParameterDefinition;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.ReportingTaskDefinition;
+import org.apache.nifi.stateless.flow.DataflowDefinition;
+import org.apache.nifi.stateless.flow.StandardStatelessFlow;
+import org.apache.nifi.stateless.flow.StatelessDataflow;
+import org.apache.nifi.stateless.repository.RepositoryContextFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Future;
+import java.util.stream.Collectors;
+
+import static java.util.Objects.requireNonNull;
+
+public class StandardStatelessEngine implements StatelessEngine<VersionedFlowSnapshot> {
+    private static final Logger logger = LoggerFactory.getLogger(StandardStatelessEngine.class);
+
+    // Member Variables injected via Builder
+    private final ExtensionManager extensionManager;
+    private final BulletinRepository bulletinRepository;
+    private final StateManagerProvider stateManagerProvider;
+    private final StringEncryptor encryptor;
+    private final FlowRegistryClient flowRegistryClient;
+    private final VariableRegistry rootVariableRegistry;
+    private final ProcessScheduler processScheduler;
+    private final KerberosConfig kerberosConfig;
+    private final FlowFileEventRepository flowFileEventRepository;
+    private final ProvenanceRepository provenanceRepository;
+    private final ExtensionRepository extensionRepository;
+
+    // Member Variables created/managed internally
+    private final ReloadComponent reloadComponent;
+    private final ValidationTrigger validationTrigger;
+
+    // Member Variables injected via initialization. Effectively final.
+    private FlowManager flowManager;
+    private ControllerServiceProvider controllerServiceProvider;
+    private ProcessContextFactory processContextFactory;
+    private RepositoryContextFactory repositoryContextFactory;
+    private boolean initialized = false;
+
+
+    private StandardStatelessEngine(final Builder builder) {
+        this.extensionManager = requireNonNull(builder.extensionManager, "Extension Manager must be provided");
+        this.bulletinRepository = requireNonNull(builder.bulletinRepository, "Bulletin Repository must be provided");
+        this.stateManagerProvider = requireNonNull(builder.stateManagerProvider, "State Manager Provider must be provided");
+        this.encryptor = requireNonNull(builder.encryptor, "Encryptor must be provided");
+        this.flowRegistryClient = requireNonNull(builder.flowRegistryClient, "Flow Registry Client must be provided");
+        this.rootVariableRegistry = requireNonNull(builder.variableRegistry, "Variable Registry must be provided");
+        this.processScheduler = requireNonNull(builder.processScheduler, "Process Scheduler must be provided");
+        this.kerberosConfig = requireNonNull(builder.kerberosConfig, "Kerberos Configuration must be provided");
+        this.flowFileEventRepository = requireNonNull(builder.flowFileEventRepository, "FlowFile Event Repository must be provided");
+        this.provenanceRepository = requireNonNull(builder.provenanceRepository, "Provenance Repository must be provided");
+        this.extensionRepository = requireNonNull(builder.extensionRepository, "Extension Repository must be provided");
+
+        this.reloadComponent = new StatelessReloadComponent();
+        this.validationTrigger = new StandardValidationTrigger(new FlowEngine(1, "Component Validation", true), () -> true);
+    }
+
+    @Override
+    public void initialize(final StatelessEngineInitializationContext initContext) {
+        this.flowManager = initContext.getFlowManager();
+        this.controllerServiceProvider = initContext.getControllerServiceProvider();
+        this.processContextFactory = initContext.getProcessContextFactory();
+        this.repositoryContextFactory = initContext.getRepositoryContextFactory();
+        this.initialized = true;
+    }
+
+    @Override
+    public StatelessDataflow createFlow(final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition, final List<ParameterOverride> parameterOverrides) {
+        if (!this.initialized) {
+            throw new IllegalStateException("Cannot create Flow without first initializing Stateless Engine");
+        }
+
+        final VersionedFlow versionedFlow = dataflowDefinition.getFlowSnapshot().getFlow();
+        logger.info("Building Dataflow {}", versionedFlow == null ? "" : versionedFlow.getName());
+
+        loadNecessaryExtensions(dataflowDefinition);
+
+        extensionManager.logClassLoaderDetails();
+
+        // Create a child group and add it to the root group. We do this, rather than interacting with the root group directly
+        // because the flow may well have Local Input/Output ports, and those are not allowed on the Root Group.
+        final ProcessGroup rootGroup = flowManager.getRootGroup();
+        final ProcessGroup childGroup = flowManager.createProcessGroup("stateless-flow");
+        childGroup.setName("Stateless Flow");
+        rootGroup.addProcessGroup(childGroup);
+
+        childGroup.updateFlow(dataflowDefinition.getFlowSnapshot(), "stateless-component-id-seed", false, true, true);
+
+        // Map existing parameter contexts by name
+        final Set<ParameterContext> parameterContexts = flowManager.getParameterContextManager().getParameterContexts();
+        final Map<String, ParameterContext> parameterContextMap = parameterContexts.stream()
+            .collect(Collectors.toMap(ParameterContext::getName, context -> context));
+
+        // Update Parameters to match those that are provided in the flow configuration, plus those overrides provided
+        final List<ParameterContextDefinition> parameterContextDefinitions = dataflowDefinition.getParameterContexts();
+        if (parameterContextDefinitions != null) {
+            parameterContextDefinitions.forEach(contextDefinition -> registerParameterContext(contextDefinition, parameterContextMap));
+        }
+
+        overrideParameters(parameterContextMap, parameterOverrides);
+
+        final List<ReportingTaskNode> reportingTaskNodes = createReportingTasks(dataflowDefinition);
+        final StandardStatelessFlow dataflow = new StandardStatelessFlow(childGroup, reportingTaskNodes, controllerServiceProvider, processContextFactory,
+            repositoryContextFactory, dataflowDefinition);
+        dataflow.initialize(processScheduler);
+        return dataflow;
+    }
+
+    private void loadNecessaryExtensions(final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition) {
+        final VersionedProcessGroup group = dataflowDefinition.getFlowSnapshot().getFlowContents();
+        final Set<BundleCoordinate> requiredBundles = gatherRequiredBundles(group);
+
+        for (final ReportingTaskDefinition reportingTaskDefinition : dataflowDefinition.getReportingTaskDefinitions()) {
+            final BundleCoordinate coordinate = parseBundleCoordinate(reportingTaskDefinition);
+            if (coordinate == null) {
+                continue;
+            }
+
+            requiredBundles.add(coordinate);
+        }
+
+        final int concurrentDownloads = 4;
+        final ExecutorService executor = new FlowEngine(concurrentDownloads, "Download Extensions", true);
+        final Future<Set<Bundle>> future = extensionRepository.fetch(requiredBundles, executor, concurrentDownloads);
+        executor.shutdown();
+
+        logger.info("Waiting for bundles to complete download...");

Review comment:
       Including the size of the requiredBundles set would be informative for logging.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/controller/ProcessScheduler.java
##########
@@ -29,6 +29,7 @@
 import org.apache.nifi.processor.ProcessContext;
 import org.apache.nifi.processor.ProcessSession;
 import org.apache.nifi.processor.ProcessSessionFactory;
+import org.apache.nifi.processor.exception.TerminatedTaskException;

Review comment:
       This import does not appear to be used.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-nar-utils/src/main/java/org/apache/nifi/nar/NarUnpacker.java
##########
@@ -109,6 +123,12 @@ public static ExtensionMapping unpackNars(final NiFiProperties props, final Bund
                     // get the manifest for this nar
                     try (final JarFile nar = new JarFile(narFile)) {
                         BundleCoordinate bundleCoordinate = createBundleCoordinate(nar.getManifest());
+
+                        if (!narFilter.test(bundleCoordinate)) {
+                            logger.info("Will not expand NAR {} because it does not match the provided filter", bundleCoordinate);

Review comment:
       Is this a common enough situation to log as info, or should this be debug?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-components/src/main/java/org/apache/nifi/groups/StandardProcessGroup.java
##########
@@ -2331,23 +2336,23 @@ public void removeControllerService(final ControllerServiceNode service) {
             // and notify the Process Group that a component has been modified. This way, we know to re-calculate
             // whether or not the Process Group has local modifications.
             service.getReferences().getReferencingComponents().stream()
-                    .map(ComponentNode::getProcessGroupIdentifier)

Review comment:
       This class contains a large number of white space formatting changes, was that intentional?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/controller/ProcessScheduler.java
##########
@@ -234,4 +235,11 @@
      * @param service to disable
      */
     CompletableFuture<Void> disableControllerService(ControllerServiceNode service);
+
+    /**
+     * Submits the given task to be executed exactly once in a background thread
+     *
+     * @param task the task to perform

Review comment:
       Missing return documentation.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-bootstrap/src/main/java/org/apache/nifi/stateless/bootstrap/StatelessBootstrap.java
##########
@@ -0,0 +1,149 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.bootstrap;
+
+import org.apache.nifi.bundle.Bundle;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.nar.NarUnpacker;
+import org.apache.nifi.nar.SystemBundle;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.flow.DataflowDefinition;
+import org.apache.nifi.stateless.flow.DataflowDefinitionParser;
+import org.apache.nifi.stateless.flow.StatelessDataflow;
+import org.apache.nifi.stateless.flow.StatelessDataflowFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.ServiceLoader;
+import java.util.function.Predicate;
+import java.util.regex.Pattern;
+
+public class StatelessBootstrap {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessBootstrap.class);
+    private static final Pattern STATELESS_NAR_PATTERN = Pattern.compile("nifi-stateless-nar-.*\\.nar-unpacked");
+    private final ClassLoader statelessClassLoader;
+    private final StatelessEngineConfiguration engineConfiguration;
+
+    private StatelessBootstrap(final ClassLoader statelessClassLoader, final StatelessEngineConfiguration engineConfiguration) {
+        this.statelessClassLoader = statelessClassLoader;
+        this.engineConfiguration = engineConfiguration;
+    }
+
+    public <T> StatelessDataflow createDataflow(final DataflowDefinition<T> dataflowDefinition, final List<ParameterOverride> parameterOverrides)
+                throws IOException, StatelessConfigurationException {
+        final StatelessDataflowFactory<T> dataflowFactory = getSingleInstance(statelessClassLoader, StatelessDataflowFactory.class);
+        final StatelessDataflow dataflow = dataflowFactory.createDataflow(engineConfiguration, dataflowDefinition, parameterOverrides);
+        return dataflow;
+    }
+
+    public DataflowDefinition<?> parseDataflowDefinition(final File flowDefinitionFile) throws StatelessConfigurationException, IOException {
+        final DataflowDefinitionParser dataflowDefinitionParser = getSingleInstance(statelessClassLoader, DataflowDefinitionParser.class);
+        final DataflowDefinition<?> dataflowDefinition = dataflowDefinitionParser.parseFlowDefinition(flowDefinitionFile, engineConfiguration);
+        return dataflowDefinition;
+    }
+
+    public static StatelessBootstrap bootstrap(final StatelessEngineConfiguration engineConfiguration) throws IOException {
+        final File narDirectory = engineConfiguration.getNarDirectory();
+        final File workingDirectory = engineConfiguration.getWorkingDirectory();
+
+        final Bundle systemBundle = SystemBundle.create(narDirectory.getAbsolutePath(), ClassLoader.getSystemClassLoader());
+        final File frameworkWorkingDir = new File(workingDirectory, "nifi-framework");
+        final File extensionsWorkingDir = new File(workingDirectory, "extensions");
+        final File docsWorkingDir = new File(workingDirectory, "documentation");
+        final List<Path> narDirectories = Collections.singletonList(narDirectory.toPath());
+
+        // Unpack NARs
+        final long unpackStart = System.currentTimeMillis();
+        final Predicate<BundleCoordinate> narFilter = coordinate -> true;
+        NarUnpacker.unpackNars(systemBundle, frameworkWorkingDir, extensionsWorkingDir, docsWorkingDir, narDirectories, false, false, narFilter);
+        final long unpackMillis = System.currentTimeMillis() - unpackStart;
+        logger.info("Unpacked NAR's in {} millis", unpackMillis);

Review comment:
       Recommend changing message to read "Unpacked NAR files in {} millis"

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-components/src/test/java/org/apache/nifi/parameter/TestStandardParameterContext.java
##########
@@ -54,12 +53,12 @@ public void testUpdatesApply() {
 
         final Parameter abcParam = context.getParameter("abc").get();
         assertEquals(abcDescriptor, abcParam.getDescriptor());
-        assertNull(abcParam.getDescriptor().getDescription());
+        Assert.assertNull(abcParam.getDescriptor().getDescription());

Review comment:
       Instead of changing these lines, what about replacing import static org.testng.Assert.assertNull with org.junit.Assert.assertNull?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/service/TestStandardControllerServiceProvider.java
##########
@@ -448,8 +429,9 @@ private ProcessorNode createProcessor(final StandardProcessScheduler scheduler,
         Mockito.when(flowController.getFlowManager()).thenReturn(flowManager);
         Mockito.when(flowController.getStateManagerProvider()).thenReturn(stateManagerProvider);
 
-        final ProcessGroup group = new StandardProcessGroup(UUID.randomUUID().toString(), serviceProvider, scheduler, null, null, flowController,
-            new MutableVariableRegistry(variableRegistry));
+//        final ProcessGroup group = new StandardProcessGroup(UUID.randomUUID().toString(), serviceProvider, scheduler, null, null, flowController,

Review comment:
       Is there a reason to leave these lines commented out as opposed to removing them?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-bootstrap/src/main/java/org/apache/nifi/stateless/bootstrap/StatelessBootstrap.java
##########
@@ -0,0 +1,149 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.bootstrap;
+
+import org.apache.nifi.bundle.Bundle;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.nar.NarUnpacker;
+import org.apache.nifi.nar.SystemBundle;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.flow.DataflowDefinition;
+import org.apache.nifi.stateless.flow.DataflowDefinitionParser;
+import org.apache.nifi.stateless.flow.StatelessDataflow;
+import org.apache.nifi.stateless.flow.StatelessDataflowFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.ServiceLoader;
+import java.util.function.Predicate;
+import java.util.regex.Pattern;
+
+public class StatelessBootstrap {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessBootstrap.class);
+    private static final Pattern STATELESS_NAR_PATTERN = Pattern.compile("nifi-stateless-nar-.*\\.nar-unpacked");
+    private final ClassLoader statelessClassLoader;
+    private final StatelessEngineConfiguration engineConfiguration;
+
+    private StatelessBootstrap(final ClassLoader statelessClassLoader, final StatelessEngineConfiguration engineConfiguration) {
+        this.statelessClassLoader = statelessClassLoader;
+        this.engineConfiguration = engineConfiguration;
+    }
+
+    public <T> StatelessDataflow createDataflow(final DataflowDefinition<T> dataflowDefinition, final List<ParameterOverride> parameterOverrides)
+                throws IOException, StatelessConfigurationException {
+        final StatelessDataflowFactory<T> dataflowFactory = getSingleInstance(statelessClassLoader, StatelessDataflowFactory.class);
+        final StatelessDataflow dataflow = dataflowFactory.createDataflow(engineConfiguration, dataflowDefinition, parameterOverrides);
+        return dataflow;
+    }
+
+    public DataflowDefinition<?> parseDataflowDefinition(final File flowDefinitionFile) throws StatelessConfigurationException, IOException {
+        final DataflowDefinitionParser dataflowDefinitionParser = getSingleInstance(statelessClassLoader, DataflowDefinitionParser.class);
+        final DataflowDefinition<?> dataflowDefinition = dataflowDefinitionParser.parseFlowDefinition(flowDefinitionFile, engineConfiguration);
+        return dataflowDefinition;
+    }
+
+    public static StatelessBootstrap bootstrap(final StatelessEngineConfiguration engineConfiguration) throws IOException {
+        final File narDirectory = engineConfiguration.getNarDirectory();
+        final File workingDirectory = engineConfiguration.getWorkingDirectory();
+
+        final Bundle systemBundle = SystemBundle.create(narDirectory.getAbsolutePath(), ClassLoader.getSystemClassLoader());
+        final File frameworkWorkingDir = new File(workingDirectory, "nifi-framework");
+        final File extensionsWorkingDir = new File(workingDirectory, "extensions");
+        final File docsWorkingDir = new File(workingDirectory, "documentation");
+        final List<Path> narDirectories = Collections.singletonList(narDirectory.toPath());
+
+        // Unpack NARs
+        final long unpackStart = System.currentTimeMillis();
+        final Predicate<BundleCoordinate> narFilter = coordinate -> true;
+        NarUnpacker.unpackNars(systemBundle, frameworkWorkingDir, extensionsWorkingDir, docsWorkingDir, narDirectories, false, false, narFilter);
+        final long unpackMillis = System.currentTimeMillis() - unpackStart;
+        logger.info("Unpacked NAR's in {} millis", unpackMillis);
+
+        final File statelessNarWorkingDir = locateStatelessNarWorkingDirectory(extensionsWorkingDir);
+        final File statelessNarInf = new File(statelessNarWorkingDir, "NAR-INF");
+        final File statelessNarDependencies = new File(statelessNarInf, "bundled-dependencies");
+        final File[] statelessNarContents = statelessNarDependencies.listFiles();
+        if (statelessNarContents == null || statelessNarContents.length == 0) {
+            throw new IOException("Could not access contents of Stateless NAR dependencies at " + statelessNarDependencies);
+        }
+
+        final URL[] urls = new URL[statelessNarContents.length];
+        for (int i=0; i < statelessNarContents.length; i++) {
+            final File dependency = statelessNarContents[i];
+            final URL url = dependency.toURI().toURL();
+            urls[i] = url;
+        }
+
+        final URLClassLoader statelessClassLoader = new URLClassLoader(urls, ClassLoader.getSystemClassLoader());
+        Thread.currentThread().setContextClassLoader(statelessClassLoader);
+        return new StatelessBootstrap(statelessClassLoader, engineConfiguration);
+    }
+
+    private static File locateStatelessNarWorkingDirectory(final File workingDirectory) throws IOException {
+        final File[] files = workingDirectory.listFiles();
+        if (files == null) {
+            throw new IOException("Could not read contents of working directory " + workingDirectory);
+        }
+
+        final List<File> matching = new ArrayList<>();
+        for (final File file : files) {
+            final String filename = file.getName();
+            if (STATELESS_NAR_PATTERN.matcher(filename).matches()) {
+                matching.add(file);
+            }
+        }
+
+        if (matching.isEmpty()) {

Review comment:
       These conditionals could be combined to a single check along the lines of: if (matching.size() == 1) { return ... } else { throw new IOException(...) }

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/StandardStatelessEngine.java
##########
@@ -0,0 +1,550 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.bundle.Bundle;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.components.AllowableValue;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.validation.StandardValidationTrigger;
+import org.apache.nifi.components.validation.ValidationTrigger;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ReloadComponent;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.flow.FlowManager;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.encrypt.StringEncryptor;
+import org.apache.nifi.engine.FlowEngine;
+import org.apache.nifi.extensions.ExtensionRepository;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.parameter.Parameter;
+import org.apache.nifi.parameter.ParameterContext;
+import org.apache.nifi.provenance.ProvenanceRepository;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.FlowRegistryClient;
+import org.apache.nifi.registry.flow.VersionedFlow;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.registry.flow.VersionedProcessGroup;
+import org.apache.nifi.reporting.BulletinRepository;
+import org.apache.nifi.reporting.ReportingTask;
+import org.apache.nifi.scheduling.SchedulingStrategy;
+import org.apache.nifi.stateless.config.ParameterContextDefinition;
+import org.apache.nifi.stateless.config.ParameterDefinition;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.ReportingTaskDefinition;
+import org.apache.nifi.stateless.flow.DataflowDefinition;
+import org.apache.nifi.stateless.flow.StandardStatelessFlow;
+import org.apache.nifi.stateless.flow.StatelessDataflow;
+import org.apache.nifi.stateless.repository.RepositoryContextFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Future;
+import java.util.stream.Collectors;
+
+import static java.util.Objects.requireNonNull;
+
+public class StandardStatelessEngine implements StatelessEngine<VersionedFlowSnapshot> {
+    private static final Logger logger = LoggerFactory.getLogger(StandardStatelessEngine.class);
+
+    // Member Variables injected via Builder
+    private final ExtensionManager extensionManager;
+    private final BulletinRepository bulletinRepository;
+    private final StateManagerProvider stateManagerProvider;
+    private final StringEncryptor encryptor;
+    private final FlowRegistryClient flowRegistryClient;
+    private final VariableRegistry rootVariableRegistry;
+    private final ProcessScheduler processScheduler;
+    private final KerberosConfig kerberosConfig;
+    private final FlowFileEventRepository flowFileEventRepository;
+    private final ProvenanceRepository provenanceRepository;
+    private final ExtensionRepository extensionRepository;
+
+    // Member Variables created/managed internally
+    private final ReloadComponent reloadComponent;
+    private final ValidationTrigger validationTrigger;
+
+    // Member Variables injected via initialization. Effectively final.
+    private FlowManager flowManager;
+    private ControllerServiceProvider controllerServiceProvider;
+    private ProcessContextFactory processContextFactory;
+    private RepositoryContextFactory repositoryContextFactory;
+    private boolean initialized = false;
+
+
+    private StandardStatelessEngine(final Builder builder) {
+        this.extensionManager = requireNonNull(builder.extensionManager, "Extension Manager must be provided");
+        this.bulletinRepository = requireNonNull(builder.bulletinRepository, "Bulletin Repository must be provided");
+        this.stateManagerProvider = requireNonNull(builder.stateManagerProvider, "State Manager Provider must be provided");
+        this.encryptor = requireNonNull(builder.encryptor, "Encryptor must be provided");
+        this.flowRegistryClient = requireNonNull(builder.flowRegistryClient, "Flow Registry Client must be provided");
+        this.rootVariableRegistry = requireNonNull(builder.variableRegistry, "Variable Registry must be provided");
+        this.processScheduler = requireNonNull(builder.processScheduler, "Process Scheduler must be provided");
+        this.kerberosConfig = requireNonNull(builder.kerberosConfig, "Kerberos Configuration must be provided");
+        this.flowFileEventRepository = requireNonNull(builder.flowFileEventRepository, "FlowFile Event Repository must be provided");
+        this.provenanceRepository = requireNonNull(builder.provenanceRepository, "Provenance Repository must be provided");
+        this.extensionRepository = requireNonNull(builder.extensionRepository, "Extension Repository must be provided");
+
+        this.reloadComponent = new StatelessReloadComponent();
+        this.validationTrigger = new StandardValidationTrigger(new FlowEngine(1, "Component Validation", true), () -> true);
+    }
+
+    @Override
+    public void initialize(final StatelessEngineInitializationContext initContext) {
+        this.flowManager = initContext.getFlowManager();
+        this.controllerServiceProvider = initContext.getControllerServiceProvider();
+        this.processContextFactory = initContext.getProcessContextFactory();
+        this.repositoryContextFactory = initContext.getRepositoryContextFactory();
+        this.initialized = true;
+    }
+
+    @Override
+    public StatelessDataflow createFlow(final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition, final List<ParameterOverride> parameterOverrides) {
+        if (!this.initialized) {
+            throw new IllegalStateException("Cannot create Flow without first initializing Stateless Engine");
+        }
+
+        final VersionedFlow versionedFlow = dataflowDefinition.getFlowSnapshot().getFlow();
+        logger.info("Building Dataflow {}", versionedFlow == null ? "" : versionedFlow.getName());
+
+        loadNecessaryExtensions(dataflowDefinition);
+
+        extensionManager.logClassLoaderDetails();
+
+        // Create a child group and add it to the root group. We do this, rather than interacting with the root group directly
+        // because the flow may well have Local Input/Output ports, and those are not allowed on the Root Group.
+        final ProcessGroup rootGroup = flowManager.getRootGroup();
+        final ProcessGroup childGroup = flowManager.createProcessGroup("stateless-flow");
+        childGroup.setName("Stateless Flow");
+        rootGroup.addProcessGroup(childGroup);
+
+        childGroup.updateFlow(dataflowDefinition.getFlowSnapshot(), "stateless-component-id-seed", false, true, true);
+
+        // Map existing parameter contexts by name
+        final Set<ParameterContext> parameterContexts = flowManager.getParameterContextManager().getParameterContexts();
+        final Map<String, ParameterContext> parameterContextMap = parameterContexts.stream()
+            .collect(Collectors.toMap(ParameterContext::getName, context -> context));
+
+        // Update Parameters to match those that are provided in the flow configuration, plus those overrides provided
+        final List<ParameterContextDefinition> parameterContextDefinitions = dataflowDefinition.getParameterContexts();
+        if (parameterContextDefinitions != null) {
+            parameterContextDefinitions.forEach(contextDefinition -> registerParameterContext(contextDefinition, parameterContextMap));
+        }
+
+        overrideParameters(parameterContextMap, parameterOverrides);
+
+        final List<ReportingTaskNode> reportingTaskNodes = createReportingTasks(dataflowDefinition);
+        final StandardStatelessFlow dataflow = new StandardStatelessFlow(childGroup, reportingTaskNodes, controllerServiceProvider, processContextFactory,
+            repositoryContextFactory, dataflowDefinition);
+        dataflow.initialize(processScheduler);
+        return dataflow;
+    }
+
+    private void loadNecessaryExtensions(final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition) {
+        final VersionedProcessGroup group = dataflowDefinition.getFlowSnapshot().getFlowContents();
+        final Set<BundleCoordinate> requiredBundles = gatherRequiredBundles(group);
+
+        for (final ReportingTaskDefinition reportingTaskDefinition : dataflowDefinition.getReportingTaskDefinitions()) {
+            final BundleCoordinate coordinate = parseBundleCoordinate(reportingTaskDefinition);
+            if (coordinate == null) {
+                continue;
+            }
+
+            requiredBundles.add(coordinate);
+        }
+
+        final int concurrentDownloads = 4;

Review comment:
       Recommend declaring this as a static final class variable since it is never changed.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/components/state/HashMapStateProvider.java
##########
@@ -0,0 +1,123 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.components.state;
+
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.components.Validator;
+import org.apache.nifi.controller.state.StandardStateMap;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+public class HashMapStateProvider implements StateProvider {
+    private final ConcurrentMap<String, StateMap> states = new ConcurrentHashMap<>();
+
+    @Override
+    public void initialize(final StateProviderInitializationContext context) {
+    }
+
+    @Override
+    public void shutdown() {
+    }
+
+    @Override
+    public void setState(final Map<String, String> state, final String componentId) {
+        final StateMap existing = states.get(componentId);
+        final long version = existing == null ? -1 : existing.getVersion();

Review comment:
       Recommend declaring a static variable equal to -1 named something like NULL_VERSION or EMPTY_VERSION and using in this method and in getState()

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/StatelessFlowManager.java
##########
@@ -0,0 +1,365 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.annotation.lifecycle.OnAdded;
+import org.apache.nifi.annotation.lifecycle.OnConfigurationRestored;
+import org.apache.nifi.authorization.resource.Authorizable;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.connectable.ConnectableType;
+import org.apache.nifi.connectable.Connection;
+import org.apache.nifi.connectable.Funnel;
+import org.apache.nifi.connectable.LocalPort;
+import org.apache.nifi.connectable.Port;
+import org.apache.nifi.connectable.StandardConnection;
+import org.apache.nifi.controller.ControllerService;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ProcessorNode;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.StandardFunnel;
+import org.apache.nifi.controller.StandardProcessorNode;
+import org.apache.nifi.controller.exception.ComponentLifeCycleException;
+import org.apache.nifi.controller.exception.ProcessorInstantiationException;
+import org.apache.nifi.controller.flow.AbstractFlowManager;
+import org.apache.nifi.controller.flow.FlowManager;
+import org.apache.nifi.controller.label.Label;
+import org.apache.nifi.controller.label.StandardLabel;
+import org.apache.nifi.controller.queue.ConnectionEventListener;
+import org.apache.nifi.controller.queue.FlowFileQueue;
+import org.apache.nifi.controller.queue.FlowFileQueueFactory;
+import org.apache.nifi.controller.queue.LoadBalanceStrategy;
+import org.apache.nifi.controller.reporting.ReportingTaskInstantiationException;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceNode;
+import org.apache.nifi.flowfile.FlowFilePrioritizer;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.groups.RemoteProcessGroup;
+import org.apache.nifi.groups.StandardProcessGroup;
+import org.apache.nifi.logging.LogRepository;
+import org.apache.nifi.logging.LogRepositoryFactory;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.nar.NarCloseable;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.registry.variable.MutableVariableRegistry;
+import org.apache.nifi.remote.StandardRemoteProcessGroup;
+import org.apache.nifi.stateless.queue.StatelessFlowFileQueue;
+import org.apache.nifi.util.ReflectionUtils;
+import org.apache.nifi.web.api.dto.FlowSnippetDTO;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.function.BooleanSupplier;
+
+import static java.util.Objects.requireNonNull;
+
+public class StatelessFlowManager extends AbstractFlowManager implements FlowManager {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessFlowManager.class);
+
+    private final StatelessEngine<VersionedFlowSnapshot> statelessEngine;
+    private final SSLContext sslContext;
+
+    public StatelessFlowManager(final FlowFileEventRepository flowFileEventRepository, final ParameterContextManager parameterContextManager,
+                                final StatelessEngine<VersionedFlowSnapshot> statelessEngine, final BooleanSupplier flowInitializedCheck,
+                                final SSLContext sslContext) {
+        super(flowFileEventRepository, parameterContextManager, statelessEngine.getFlowRegistryClient(), flowInitializedCheck);
+
+        this.statelessEngine = statelessEngine;
+        this.sslContext = sslContext;
+    }
+
+    @Override
+    public Port createPublicInputPort(final String id, final String name) {
+        throw new UnsupportedOperationException("Create create Public Input Port with name '" + name + "' because Public Input Ports and Public Output Ports are not supported in Stateless NiFi");
+    }
+
+    @Override
+    public Port createPublicOutputPort(final String id, final String name) {
+        throw new UnsupportedOperationException("Create create Public Input Port with name '" + name + "' because Public Input Ports and Public Output Ports are not supported in Stateless NiFi");
+    }
+
+    @Override
+    public Set<Port> getPublicInputPorts() {
+        return Collections.emptySet();
+    }
+
+    @Override
+    public Set<Port> getPublicOutputPorts() {
+        return Collections.emptySet();
+    }
+
+    @Override
+    public Optional<Port> getPublicInputPort(final String name) {
+        return Optional.empty();
+    }
+
+    @Override
+    public Optional<Port> getPublicOutputPort(final String name) {
+        return Optional.empty();
+    }
+
+    @Override
+    public RemoteProcessGroup createRemoteProcessGroup(final String id, final String uris) {
+        return new StandardRemoteProcessGroup(id, uris, null, statelessEngine.getProcessScheduler(), statelessEngine.getBulletinRepository(), sslContext,
+            statelessEngine.getStateManagerProvider().getStateManager(id), TimeUnit.SECONDS.toMillis(30));
+    }
+
+    @Override
+    public void instantiateSnippet(final ProcessGroup group, final FlowSnippetDTO dto) {
+        throw new UnsupportedOperationException("Flow Snippets are not supported in Stateless NiFi");
+    }
+
+    @Override
+    public FlowFilePrioritizer createPrioritizer(final String type) {
+        // This will never actually be used, as the the Stateless FlowFile Queues will not take prioritizers into account.
+        // However, we avoid returning null in order to ensure that we don't encounter any NullPointerExceptions, etc.
+        return (o1, o2) -> o1.getLastQueueDate().compareTo(o2.getLastQueueDate());
+    }
+
+    @Override
+    public ProcessorNode createProcessor(final String type, final String id, final BundleCoordinate coordinate, final Set<URL> additionalUrls, final boolean firstTimeAdded,
+                                         final boolean registerLogObserver) {
+        logger.debug("Creating Processor of type {} with id {}", type, id);
+
+        // make sure the first reference to LogRepository happens outside of a NarCloseable so that we use the framework's ClassLoader
+        final LogRepository logRepository = LogRepositoryFactory.getRepository(id);
+        final ExtensionManager extensionManager = statelessEngine.getExtensionManager();
+
+        try {
+            final ProcessorNode procNode = new ComponentBuilder()
+                .identifier(id)
+                .type(type)
+                .bundleCoordinate(coordinate)
+                .statelessEngine(statelessEngine)
+                .additionalClassPathUrls(additionalUrls)
+                .buildProcessor();
+
+            try (final NarCloseable x = NarCloseable.withComponentNarLoader(extensionManager, procNode.getProcessor().getClass(), procNode.getProcessor().getIdentifier())) {
+                ReflectionUtils.invokeMethodsWithAnnotation(OnAdded.class, procNode.getProcessor());
+            } catch (final Exception e) {
+                if (registerLogObserver) {
+                    logRepository.removeObserver(StandardProcessorNode.BULLETIN_OBSERVER_ID);
+                }
+
+                throw new ComponentLifeCycleException("Failed to invoke @OnAdded methods of " + procNode.getProcessor(), e);
+            }
+
+            try (final NarCloseable nc = NarCloseable.withComponentNarLoader(extensionManager, procNode.getProcessor().getClass(), procNode.getProcessor().getIdentifier())) {
+                ReflectionUtils.quietlyInvokeMethodsWithAnnotation(OnConfigurationRestored.class, procNode.getProcessor());
+            }
+
+            logger.debug("Processor with id {} successfully created", id);
+
+            return procNode;
+        } catch (final ProcessorInstantiationException e) {
+            throw new IllegalStateException("Could not create Processor of type " + type, e);
+        }
+    }
+
+    @Override
+    public Label createLabel(final String id, final String text) {
+        return new StandardLabel(id, text);
+    }
+
+    @Override
+    public Funnel createFunnel(final String id) {
+        return new StandardFunnel(id, 1, 50000);
+    }
+
+    @Override
+    public Port createLocalInputPort(final String id, final String name) {
+        return new LocalPort(id, name, ConnectableType.INPUT_PORT, statelessEngine.getProcessScheduler(), 1, 50000, "10 millis");
+
+    }
+
+    @Override
+    public Port createLocalOutputPort(final String id, final String name) {
+        return new LocalPort(id, name, ConnectableType.OUTPUT_PORT, statelessEngine.getProcessScheduler(), 1, 50000, "10 millis");
+    }
+
+    @Override
+    public ProcessGroup createProcessGroup(final String id) {
+        final MutableVariableRegistry mutableVariableRegistry = new MutableVariableRegistry(statelessEngine.getRootVariableRegistry());
+
+        return new StandardProcessGroup(id, statelessEngine.getControllerServiceProvider(),
+            statelessEngine.getProcessScheduler(),
+            statelessEngine.getEncryptor(),
+            statelessEngine.getExtensionManager(),
+            statelessEngine.getStateManagerProvider(),
+            this,
+            statelessEngine.getFlowRegistryClient(),
+            statelessEngine.getReloadComponent(),
+            mutableVariableRegistry,
+            new StatelessNodeTypeProvider());
+    }
+
+    @Override
+    public Connection createConnection(final String id, final String name, final Connectable source, final Connectable destination, final Collection<String> relationshipNames) {
+        final StandardConnection.Builder builder = new StandardConnection.Builder(statelessEngine.getProcessScheduler());
+
+        final List<Relationship> relationships = new ArrayList<>();
+        for (final String relationshipName : requireNonNull(relationshipNames)) {
+            relationships.add(new Relationship.Builder().name(relationshipName).build());
+        }
+
+        final FlowFileQueueFactory flowFileQueueFactory = new FlowFileQueueFactory() {
+            @Override
+            public FlowFileQueue createFlowFileQueue(final LoadBalanceStrategy loadBalanceStrategy, final String partitioningAttribute, final ConnectionEventListener eventListener) {
+                return new StatelessFlowFileQueue(id);
+            }
+        };
+
+        final Connection connection = builder.id(requireNonNull(id).intern())
+            .name(name == null ? null : name.intern())
+            .relationships(relationships)
+            .source(requireNonNull(source))
+            .destination(destination)
+            .flowFileQueueFactory(flowFileQueueFactory)
+            .build();
+
+        return connection;
+    }
+
+    @Override
+    public ReportingTaskNode createReportingTask(final String type, final String id, final BundleCoordinate bundleCoordinate, final Set<URL> additionalUrls, final boolean firstTimeAdded,
+                                                 final boolean register) {
+
+        if (type == null || id == null || bundleCoordinate == null) {
+            throw new NullPointerException();

Review comment:
       It would be helpful to include the values of type, id, and bundleCoordinate in the exception message for easier troubleshooting.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/registry/flow/InMemoryFlowRegistry.java
##########
@@ -0,0 +1,207 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.registry.flow;
+
+import org.apache.nifi.authorization.user.NiFiUser;
+import org.apache.nifi.registry.bucket.Bucket;
+import org.apache.nifi.registry.client.NiFiRegistryException;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class InMemoryFlowRegistry implements FlowRegistry {
+    private final AtomicInteger flowIdGenerator = new AtomicInteger(1);
+    private static final String DEFAULT_BUCKET_ID = "stateless-bucket-1";
+
+    private volatile String description;
+    private volatile String name;
+    private volatile String url;
+
+    private final Map<FlowCoordinates, List<VersionedFlowSnapshot>> flowSnapshots = new ConcurrentHashMap<>();
+
+    @Override
+    public String getIdentifier() {
+        return "in-memory-flow-registry";
+    }
+
+    @Override
+    public String getDescription() {
+        return description;
+    }
+
+    @Override
+    public void setDescription(final String description) {
+        this.description = description;
+    }
+
+    @Override
+    public String getURL() {
+        return url;
+    }
+
+    @Override
+    public void setURL(final String url) {
+        this.url = url;
+    }
+
+    @Override
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public void setName(final String name) {
+        this.name = name;
+    }
+
+    @Override
+    public Set<Bucket> getBuckets(final NiFiUser user) {
+        throw new UnsupportedOperationException("User-specific actions are not implemented with this Registry");

Review comment:
       Recommend declaring a static error message string and reusing it for applicable UnsupportedOperationExceptions

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core-api/src/main/java/org/apache/nifi/provenance/InternalProvenanceReporter.java
##########
@@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.provenance;
+
+import org.apache.nifi.flowfile.FlowFile;
+
+import java.util.Collection;
+import java.util.Set;
+
+/**
+ * An extension of the ProvenanceReporter that provides methods that are meant to be used only internally by the framework
+ * and not by the extensions that have access to the Provenance Reporter.
+ */
+public interface InternalProvenanceReporter extends ProvenanceReporter {
+    ProvenanceEventRecord generateDropEvent(FlowFile flowFile, String explanation);
+
+    void clone(FlowFile parent, FlowFile child, boolean verifyFlowFile);
+
+    ProvenanceEventRecord generateJoinEvent(Collection<FlowFile> parents, FlowFile child);
+
+    void remove(final ProvenanceEventRecord event);

Review comment:
       The final keyword is not necessary on interface methods.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/extensions/NexusExtensionClient.java
##########
@@ -0,0 +1,137 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.extensions;
+
+import okhttp3.Call;
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.Response;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.security.util.OkHttpClientUtils;
+import org.apache.nifi.security.util.TlsConfiguration;
+import org.apache.nifi.stateless.config.SslConfigurationUtil;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+import org.apache.nifi.util.FormatUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+import java.util.concurrent.TimeUnit;
+
+public class NexusExtensionClient implements ExtensionClient {
+    private static final Logger logger = LoggerFactory.getLogger(NexusExtensionClient.class);
+    private static final long DEFAULT_TIMEOUT_MILLIS = TimeUnit.SECONDS.toMillis(30);
+    private static final String URL_CHARSET = "UTF-8";
+
+    private final String baseUrl;
+    private final long timeoutMillis;
+    private final SslContextDefinition sslContextDefinition;
+
+    public NexusExtensionClient(final String baseUrl, final SslContextDefinition sslContextDefinition, final String timeout) {
+        this.baseUrl = baseUrl;
+        this.sslContextDefinition = sslContextDefinition;
+        this.timeoutMillis = timeout == null ? DEFAULT_TIMEOUT_MILLIS : FormatUtils.getTimeDuration(timeout, TimeUnit.MILLISECONDS);
+    }
+
+    @Override
+    public InputStream getExtension(final BundleCoordinate bundleCoordinate) throws IOException {
+        final String url = resolveUrl(bundleCoordinate);
+        logger.debug("Attempting to fetch {} from {}", bundleCoordinate, url);
+
+        final OkHttpClient okHttpClient = createClient();
+        final Request request = new Request.Builder()
+            .get()
+            .url(url)
+            .build();
+
+        final Call call = okHttpClient.newCall(request);
+        final Response response = call.execute();
+        if (response.isSuccessful() && response.body() != null) {
+            logger.debug("Successfully obtained stream for extension {} from {}", bundleCoordinate, url);
+            final InputStream extensionByteStream = response.body().byteStream();
+            return new FilterInputStream(extensionByteStream) {
+                @Override
+                public void close() throws IOException {
+                    response.close();
+                    super.close();
+                }
+            };
+        } else {
+            try {
+                if (response.code() == javax.ws.rs.core.Response.Status.NOT_FOUND.getStatusCode()) {

Review comment:
       The javax.ws.rs.core.Response.Status.NOT_FOUND could be referenced through an import static declaration.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/session/StatelessProcessSession.java
##########
@@ -0,0 +1,173 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.session;
+
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.connectable.ConnectableType;
+import org.apache.nifi.connectable.Connection;
+import org.apache.nifi.controller.repository.FlowFileRecord;
+import org.apache.nifi.controller.repository.RepositoryContext;
+import org.apache.nifi.controller.repository.StandardProcessSession;
+import org.apache.nifi.controller.repository.metrics.StandardFlowFileEvent;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSessionFactory;
+import org.apache.nifi.stateless.engine.ProcessContextFactory;
+import org.apache.nifi.stateless.flow.FailurePortEncounteredException;
+import org.apache.nifi.stateless.queue.DrainableFlowFileQueue;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+
+public class StatelessProcessSession extends StandardProcessSession {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessProcessSession.class);
+    private static final String PARENT_FLOW_GROUP_ID = "stateless-flow";
+
+    private final RepositoryContext context;
+    private final StatelessProcessSessionFactory sessionFactory;
+    private final ProcessContextFactory processContextFactory;
+    private final Set<String> failurePortNames;
+
+    public StatelessProcessSession(final RepositoryContext context, final StatelessProcessSessionFactory sessionFactory, final ProcessContextFactory processContextFactory,
+                                   final Set<String> failurePortNames) {
+        super(context, () -> false);
+        this.context = context;
+        this.sessionFactory = sessionFactory;
+        this.processContextFactory = processContextFactory;
+        this.failurePortNames = failurePortNames;
+    }
+
+    @Override
+    protected void commit(final StandardProcessSession.Checkpoint checkpoint) {
+        super.commit(checkpoint);
+
+        final long followOnStart = System.nanoTime();
+        for (final Connection connection : context.getConnectable().getConnections()) {
+            while (!connection.getFlowFileQueue().isEmpty()) {
+                final Connectable connectable = connection.getDestination();
+                if (isTerminalPort(connectable)) {
+                    if (failurePortNames.contains(connectable.getName())) {
+                        abortProcessing();
+                        throw new FailurePortEncounteredException("Flow failed because a FlowFile was routed from " + connection.getSource() + " to Failure Port " + connection.getDestination());
+                    }
+
+                    break;
+                }
+
+                final ProcessContext connectableContext = processContextFactory.createProcessContext(connectable);
+                final ProcessSessionFactory connectableSessionFactory = new StatelessProcessSessionFactory(connectable, this.sessionFactory.getRepositoryContextFactory(),
+                    processContextFactory, failurePortNames);
+
+                logger.debug("Triggering {}", connectable);
+                final long start = System.nanoTime();
+                try {
+                    connectable.onTrigger(connectableContext, connectableSessionFactory);
+                } catch (final Throwable t) {
+                    abortProcessing();
+                    throw t;
+                }
+
+                final long nanos = System.nanoTime() - start;
+                registerProcessEvent(connectable, nanos);
+            }
+        }
+
+        // When this component finishes running, the flowfile event repo will be updated to include the number of nanoseconds it took to
+        // trigger this component. But that will include the amount of time that it took to trigger follow-on components as well.
+        // Because we want to include only the time it took for this component, subtract away the amount of time that it took for
+        // follow-on components.
+        // Note that for a period of time, this could result in showing a negative amount of time for the current component to complete,
+        // since the subtraction will be performed before the addition of the time the current component was run. But this is an approximation,
+        // and it's probably the best that we can do without either introducing a very ugly hack or significantly changing the API.
+        final long followOnNanos = System.nanoTime() - followOnStart;
+        registerProcessEvent(context.getConnectable(), -followOnNanos);
+    }
+
+    private void abortProcessing() {
+        try {
+            rollback(false, true);
+        } finally {
+            purgeFlowFiles();
+        }
+    }
+
+    private void purgeFlowFiles() {
+        final ProcessGroup rootGroup = getRootGroup();
+        final List<Connection> allConnections = rootGroup.findAllConnections();
+        for (final Connection connection : allConnections) {
+            final DrainableFlowFileQueue flowFileQueue = (DrainableFlowFileQueue) connection.getFlowFileQueue();
+            final List<FlowFileRecord> flowFileRecords = new ArrayList<>(flowFileQueue.size().getObjectCount());
+            flowFileQueue.drainTo(flowFileRecords);
+
+            for (final FlowFileRecord flowFileRecord : flowFileRecords) {
+                context.getContentRepository().decrementClaimantCount(flowFileRecord.getContentClaim());
+            }
+        }
+    }
+
+    private ProcessGroup getRootGroup() {
+        final Connectable connectable = context.getConnectable();
+        final ProcessGroup group = connectable.getProcessGroup();
+        return getRootGroup(group);
+    }
+
+    private ProcessGroup getRootGroup(final ProcessGroup group) {
+        final ProcessGroup parent = group.getParent();
+        if (parent == null) {
+            return group;
+        }
+
+        return getRootGroup(parent);
+    }
+
+    private void registerProcessEvent(final Connectable connectable, final long processingNanos) {
+        try {
+            final StandardFlowFileEvent procEvent = new StandardFlowFileEvent();
+            procEvent.setProcessingNanos(processingNanos);
+            procEvent.setInvocations(1);
+            context.getFlowFileEventRepository().updateRepository(procEvent, connectable.getIdentifier());
+        } catch (final IOException e) {
+            logger.error("Unable to update FlowFileEvent Repository for {}; statistics may be inaccurate. Reason for failure: {}", connectable.getRunnableComponent(), e.toString(), e);
+            logger.error("", e);

Review comment:
       Is there a reason for logging an empty string with the same exception again?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/StatelessFlowManager.java
##########
@@ -0,0 +1,365 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.annotation.lifecycle.OnAdded;
+import org.apache.nifi.annotation.lifecycle.OnConfigurationRestored;
+import org.apache.nifi.authorization.resource.Authorizable;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.connectable.ConnectableType;
+import org.apache.nifi.connectable.Connection;
+import org.apache.nifi.connectable.Funnel;
+import org.apache.nifi.connectable.LocalPort;
+import org.apache.nifi.connectable.Port;
+import org.apache.nifi.connectable.StandardConnection;
+import org.apache.nifi.controller.ControllerService;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ProcessorNode;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.StandardFunnel;
+import org.apache.nifi.controller.StandardProcessorNode;
+import org.apache.nifi.controller.exception.ComponentLifeCycleException;
+import org.apache.nifi.controller.exception.ProcessorInstantiationException;
+import org.apache.nifi.controller.flow.AbstractFlowManager;
+import org.apache.nifi.controller.flow.FlowManager;
+import org.apache.nifi.controller.label.Label;
+import org.apache.nifi.controller.label.StandardLabel;
+import org.apache.nifi.controller.queue.ConnectionEventListener;
+import org.apache.nifi.controller.queue.FlowFileQueue;
+import org.apache.nifi.controller.queue.FlowFileQueueFactory;
+import org.apache.nifi.controller.queue.LoadBalanceStrategy;
+import org.apache.nifi.controller.reporting.ReportingTaskInstantiationException;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceNode;
+import org.apache.nifi.flowfile.FlowFilePrioritizer;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.groups.RemoteProcessGroup;
+import org.apache.nifi.groups.StandardProcessGroup;
+import org.apache.nifi.logging.LogRepository;
+import org.apache.nifi.logging.LogRepositoryFactory;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.nar.NarCloseable;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.registry.variable.MutableVariableRegistry;
+import org.apache.nifi.remote.StandardRemoteProcessGroup;
+import org.apache.nifi.stateless.queue.StatelessFlowFileQueue;
+import org.apache.nifi.util.ReflectionUtils;
+import org.apache.nifi.web.api.dto.FlowSnippetDTO;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.function.BooleanSupplier;
+
+import static java.util.Objects.requireNonNull;
+
+public class StatelessFlowManager extends AbstractFlowManager implements FlowManager {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessFlowManager.class);
+
+    private final StatelessEngine<VersionedFlowSnapshot> statelessEngine;
+    private final SSLContext sslContext;
+
+    public StatelessFlowManager(final FlowFileEventRepository flowFileEventRepository, final ParameterContextManager parameterContextManager,
+                                final StatelessEngine<VersionedFlowSnapshot> statelessEngine, final BooleanSupplier flowInitializedCheck,
+                                final SSLContext sslContext) {
+        super(flowFileEventRepository, parameterContextManager, statelessEngine.getFlowRegistryClient(), flowInitializedCheck);
+
+        this.statelessEngine = statelessEngine;
+        this.sslContext = sslContext;
+    }
+
+    @Override
+    public Port createPublicInputPort(final String id, final String name) {
+        throw new UnsupportedOperationException("Create create Public Input Port with name '" + name + "' because Public Input Ports and Public Output Ports are not supported in Stateless NiFi");

Review comment:
       Recommend adjusting the message to start with "Public Input Port ID [%s] Name [%s] create failed because Public Input Ports and Public Output Ports are not supported in Stateless NiFi"

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/flow/StandardStatelessDataflowFactory.java
##########
@@ -0,0 +1,306 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.flow;
+
+import org.apache.nifi.components.state.HashMapStateProvider;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.state.StateProvider;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.repository.ContentRepository;
+import org.apache.nifi.controller.repository.CounterRepository;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.repository.FlowFileRepository;
+import org.apache.nifi.controller.repository.StandardCounterRepository;
+import org.apache.nifi.controller.repository.claim.ResourceClaimManager;
+import org.apache.nifi.controller.repository.claim.StandardResourceClaimManager;
+import org.apache.nifi.controller.repository.metrics.RingBufferEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.controller.service.StandardControllerServiceProvider;
+import org.apache.nifi.controller.state.manager.StandardStateManagerProvider;
+import org.apache.nifi.encrypt.StringEncryptor;
+import org.apache.nifi.events.EventReporter;
+import org.apache.nifi.events.VolatileBulletinRepository;
+import org.apache.nifi.extensions.ExtensionClient;
+import org.apache.nifi.extensions.ExtensionRepository;
+import org.apache.nifi.extensions.FileSystemExtensionRepository;
+import org.apache.nifi.extensions.NexusExtensionClient;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.nar.ExtensionDiscoveringManager;
+import org.apache.nifi.nar.NarClassLoaders;
+import org.apache.nifi.nar.NarClassLoadersHolder;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.parameter.StandardParameterContextManager;
+import org.apache.nifi.provenance.IdentifierLookup;
+import org.apache.nifi.provenance.ProvenanceRepository;
+import org.apache.nifi.provenance.VolatileProvenanceRepository;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.FlowRegistryClient;
+import org.apache.nifi.registry.flow.InMemoryFlowRegistry;
+import org.apache.nifi.registry.flow.StandardFlowRegistryClient;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.reporting.BulletinRepository;
+import org.apache.nifi.stateless.bootstrap.ExtensionDiscovery;
+import org.apache.nifi.stateless.config.ExtensionClientDefinition;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.SslConfigurationUtil;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.CachingProcessContextFactory;
+import org.apache.nifi.stateless.engine.ProcessContextFactory;
+import org.apache.nifi.stateless.engine.StandardStatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessAuthorizer;
+import org.apache.nifi.stateless.engine.StatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.engine.StatelessEngineInitializationContext;
+import org.apache.nifi.stateless.engine.StatelessFlowManager;
+import org.apache.nifi.stateless.engine.StatelessProcessContextFactory;
+import org.apache.nifi.stateless.engine.StatelessProcessScheduler;
+import org.apache.nifi.stateless.engine.StatelessProvenanceAuthorizableFactory;
+import org.apache.nifi.stateless.repository.ByteArrayContentRepository;
+import org.apache.nifi.stateless.repository.RepositoryContextFactory;
+import org.apache.nifi.stateless.repository.StatelessFlowFileRepository;
+import org.apache.nifi.stateless.repository.StatelessRepositoryContextFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.ArrayList;
+import java.util.List;
+
+public class StandardStatelessDataflowFactory implements StatelessDataflowFactory<VersionedFlowSnapshot> {
+    private static final Logger logger = LoggerFactory.getLogger(StandardStatelessDataflowFactory.class);
+
+    @Override
+    public StatelessDataflow createDataflow(final StatelessEngineConfiguration engineConfiguration, final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition,
+                                            final List<ParameterOverride> parameterOverrides) throws IOException, StatelessConfigurationException {
+        final long start = System.currentTimeMillis();
+
+        final VersionedFlowSnapshot flowSnapshot = dataflowDefinition.getFlowSnapshot();
+
+        ProvenanceRepository provenanceRepo = null;
+        ContentRepository contentRepo = null;
+        StatelessProcessScheduler processScheduler = null;
+        FlowFileRepository flowFileRepo = null;
+        FlowFileEventRepository flowFileEventRepo = null;
+
+        try {
+            final BulletinRepository bulletinRepository = new VolatileBulletinRepository();
+            final File workingDir = engineConfiguration.getWorkingDirectory();
+            if (!workingDir.exists() && !workingDir.mkdirs()) {
+                throw new IOException("Working Directory " + workingDir + " does not exist and could not be created");
+            }
+
+            final InMemoryFlowRegistry flowRegistry = new InMemoryFlowRegistry();
+            flowRegistry.addFlowSnapshot(flowSnapshot);
+            final FlowRegistryClient flowRegistryClient = new StandardFlowRegistryClient();
+            flowRegistryClient.addFlowRegistry(flowRegistry);
+
+            final File extensionsWorkingDir = new File(workingDir, "extensions");
+            final ClassLoader systemClassLoader = createSystemClassLoader(engineConfiguration.getNarDirectory());
+            final ExtensionDiscoveringManager extensionManager = ExtensionDiscovery.discover(extensionsWorkingDir, systemClassLoader);
+
+            flowFileEventRepo = new RingBufferEventRepository(5);
+
+            final StateProvider stateProvider = new HashMapStateProvider();
+            final StateManagerProvider stateManagerProvider = new StandardStateManagerProvider(stateProvider, stateProvider);
+
+            final ParameterContextManager parameterContextManager = new StandardParameterContextManager();
+            processScheduler = new StatelessProcessScheduler(extensionManager);
+            provenanceRepo = new VolatileProvenanceRepository(1_000, "", "");
+            provenanceRepo.initialize(EventReporter.NO_OP, new StatelessAuthorizer(), new StatelessProvenanceAuthorizableFactory(), IdentifierLookup.EMPTY);
+
+            final SSLContext sslContext;
+            try {
+                sslContext = SslConfigurationUtil.createSslContext(engineConfiguration.getSslContext());
+            } catch (StatelessConfigurationException e) {
+                throw new StatelessConfigurationException("Could not create SSLContext", e);
+            }
+
+            // Build Extension Repository
+            final NarClassLoaders narClassLoaders = NarClassLoadersHolder.getInstance();
+            final List<ExtensionClient> extensionClients = new ArrayList<>();
+            for (final ExtensionClientDefinition extensionClientDefinition : engineConfiguration.getExtensionClients()) {
+                final ExtensionClient extensionClient = createExtensionClient(extensionClientDefinition, engineConfiguration.getSslContext());
+                extensionClients.add(extensionClient);
+            }
+
+            final ExtensionRepository extensionRepository = new FileSystemExtensionRepository(extensionManager, engineConfiguration.getNarDirectory(), engineConfiguration.getWorkingDirectory(),
+                narClassLoaders, extensionClients);
+
+            final VariableRegistry variableRegistry = VariableRegistry.EMPTY_REGISTRY;
+            final StringEncryptor encryptor = StringEncryptor.createEncryptor("PBEWITHMD5AND256BITAES-CBC-OPENSSL", "BC", engineConfiguration.getSensitivePropsKey());
+
+            final File krb5File = engineConfiguration.getKrb5File();
+            final KerberosConfig kerberosConfig = new KerberosConfig(null, null, krb5File);
+            logger.info("Setting java.security.krb5.conf to {}", krb5File.getAbsolutePath());
+            System.setProperty("java.security.krb5.conf", krb5File.getAbsolutePath());
+
+            final StatelessEngine<VersionedFlowSnapshot> statelessEngine = new StandardStatelessEngine.Builder()
+                .bulletinRepository(bulletinRepository)
+                .encryptor(encryptor)
+                .extensionManager(extensionManager)
+                .flowRegistryClient(flowRegistryClient)
+                .stateManagerProvider(stateManagerProvider)
+                .variableRegistry(variableRegistry)
+                .processScheduler(processScheduler)
+                .kerberosConfiguration(kerberosConfig)
+                .flowFileEventRepository(flowFileEventRepo)
+                .provenanceRepository(provenanceRepo)
+                .extensionRepository(extensionRepository)
+                .build();
+
+            final StatelessFlowManager flowManager = new StatelessFlowManager(flowFileEventRepo, parameterContextManager, statelessEngine, () -> true, sslContext);
+            final ControllerServiceProvider controllerServiceProvider = new StandardControllerServiceProvider(processScheduler, bulletinRepository, flowManager, extensionManager);
+
+            final ProcessContextFactory rawProcessContextFactory = new StatelessProcessContextFactory(controllerServiceProvider, encryptor, stateManagerProvider);
+            final ProcessContextFactory processContextFactory = new CachingProcessContextFactory(rawProcessContextFactory);
+            contentRepo = new ByteArrayContentRepository();
+            flowFileRepo = new StatelessFlowFileRepository();
+            final CounterRepository counterRepo = new StandardCounterRepository();
+
+            final RepositoryContextFactory repositoryContextFactory = new StatelessRepositoryContextFactory(contentRepo, flowFileRepo, flowFileEventRepo, counterRepo, provenanceRepo);
+            final StatelessEngineInitializationContext statelessEngineInitializationContext = new StatelessEngineInitializationContext(controllerServiceProvider, flowManager, processContextFactory,
+                repositoryContextFactory);
+
+            processScheduler.initialize(processContextFactory);
+            statelessEngine.initialize(statelessEngineInitializationContext);
+
+            // Initialize components. This is generally needed because of the interdependencies between the components.
+            // There are some circular dependencies that are resolved by passing objects via initialization rather than by providing to the constructors.
+            final ResourceClaimManager resourceClaimManager = new StandardResourceClaimManager();
+            contentRepo.initialize(resourceClaimManager);
+            flowFileRepo.initialize(resourceClaimManager);
+            flowManager.initialize(controllerServiceProvider);
+
+            // Create flow
+            final ProcessGroup rootGroup = flowManager.createProcessGroup("root");
+            rootGroup.setName("root");
+            flowManager.setRootGroup(rootGroup);
+
+            final StatelessDataflow dataflow = statelessEngine.createFlow(dataflowDefinition, parameterOverrides);
+            final long millis = System.currentTimeMillis() - start;
+            logger.info("NiFi Stateless Engine and Dataflow created and initialized in {} millis", millis);
+
+            return dataflow;
+        } catch (final Exception e) {
+            try {
+                if (provenanceRepo != null) {
+                    provenanceRepo.close();
+                }
+            } catch (final IOException ioe) {
+                e.addSuppressed(ioe);
+            }
+
+            if (contentRepo != null) {
+                contentRepo.shutdown();
+            }
+
+            if (processScheduler != null) {
+                processScheduler.shutdown();
+            }
+
+            if (flowFileRepo != null) {
+                try {
+                    flowFileRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            if (flowFileEventRepo != null) {
+                try {
+                    flowFileEventRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            throw e;
+        }
+    }
+
+    private ExtensionClient createExtensionClient(final ExtensionClientDefinition definition, final SslContextDefinition sslContextDefinition) {
+        final String type = definition.getExtensionClientType();
+        if (!"nexus".equalsIgnoreCase(type.trim())) {
+            throw new IllegalArgumentException("Invalid Extension Client type: <" + definition.getExtensionClientType() +">. Currently, the only supported type is <nexus>");
+        }
+
+        final SslContextDefinition sslContext = (definition.isUseSslContext() && sslContextDefinition != null) ? sslContextDefinition : null;
+        return new NexusExtensionClient(definition.getBaseUrl(), sslContext, definition.getCommsTimeout());
+    }
+
+    private ClassLoader createSystemClassLoader(final File narDirectory) throws StatelessConfigurationException {
+        final ClassLoader systemClassLoader = StatelessDataflowFactory.class.getClassLoader();
+        final int javaMajorVersion = getJavaMajorVersion();
+        if (javaMajorVersion >= 11) {

Review comment:
       Perhaps refactor this check into a method named something like isRecentJavaVersion() or requiresAdditionalNars() would help indicate the reason for this approach, in addition to the existing comment provided.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/ComponentBuilder.java
##########
@@ -0,0 +1,286 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.commons.lang3.ClassUtils;
+import org.apache.nifi.bundle.Bundle;
+import org.apache.nifi.bundle.BundleCoordinate;
+import org.apache.nifi.components.ConfigurableComponent;
+import org.apache.nifi.components.state.StateManager;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.validation.ValidationTrigger;
+import org.apache.nifi.controller.ControllerService;
+import org.apache.nifi.controller.ControllerServiceInitializationContext;
+import org.apache.nifi.controller.LoggableComponent;
+import org.apache.nifi.controller.NodeTypeProvider;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ProcessorNode;
+import org.apache.nifi.controller.ReloadComponent;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.StandardProcessorNode;
+import org.apache.nifi.controller.TerminationAwareLogger;
+import org.apache.nifi.controller.ValidationContextFactory;
+import org.apache.nifi.controller.exception.ControllerServiceInstantiationException;
+import org.apache.nifi.controller.exception.ProcessorInstantiationException;
+import org.apache.nifi.controller.flow.FlowManager;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.reporting.ReportingTaskInstantiationException;
+import org.apache.nifi.controller.reporting.StandardReportingInitializationContext;
+import org.apache.nifi.controller.reporting.StatelessReportingTaskNode;
+import org.apache.nifi.controller.service.ControllerServiceNode;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.controller.service.StandardControllerServiceInitializationContext;
+import org.apache.nifi.controller.service.StandardControllerServiceInvocationHandler;
+import org.apache.nifi.controller.service.StandardControllerServiceNode;
+import org.apache.nifi.logging.ComponentLog;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.processor.Processor;
+import org.apache.nifi.processor.ProcessorInitializationContext;
+import org.apache.nifi.processor.SimpleProcessLogger;
+import org.apache.nifi.processor.StandardProcessorInitializationContext;
+import org.apache.nifi.processor.StandardValidationContextFactory;
+import org.apache.nifi.registry.ComponentVariableRegistry;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.registry.variable.StandardComponentVariableRegistry;
+import org.apache.nifi.reporting.ReportingInitializationContext;
+import org.apache.nifi.reporting.ReportingTask;
+import org.apache.nifi.scheduling.SchedulingStrategy;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.Proxy;
+import java.net.URL;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+
+public class ComponentBuilder {
+    private static final Logger logger = LoggerFactory.getLogger(ComponentBuilder.class);
+
+    private StatelessEngine<VersionedFlowSnapshot> statelessEngine;
+    private FlowManager flowManager;
+    private String identifier;
+    private String type;
+    private BundleCoordinate bundleCoordinate;
+    private Set<URL> additionalClassPathUrls;
+
+    public ComponentBuilder statelessEngine(final StatelessEngine<VersionedFlowSnapshot> statelessEngine) {
+        this.statelessEngine = statelessEngine;
+        return this;
+    }
+
+    public ComponentBuilder identifier(final String identifier) {
+        this.identifier = identifier;
+        return this;
+    }
+
+    public ComponentBuilder type(final String type) {
+        this.type = type;
+        return this;
+    }
+
+    public ComponentBuilder bundleCoordinate(final BundleCoordinate bundleCoordinate) {
+        this.bundleCoordinate = bundleCoordinate;
+        return this;
+    }
+
+    public ComponentBuilder additionalClassPathUrls(final Set<URL> additionalClassPathUrls) {
+        this.additionalClassPathUrls = additionalClassPathUrls;
+        return this;
+    }
+
+    public ComponentBuilder flowManager(final FlowManager flowManager) {
+        this.flowManager = flowManager;
+        return this;
+    }
+
+    public ProcessorNode buildProcessor() throws ProcessorInstantiationException {
+        final LoggableComponent<Processor> loggableProcessor = createLoggableProcessor();
+        final ProcessScheduler processScheduler = statelessEngine.getProcessScheduler();
+        final ControllerServiceProvider controllerServiceProvider = statelessEngine.getControllerServiceProvider();
+        final ComponentVariableRegistry componentVariableRegistry = new StandardComponentVariableRegistry(statelessEngine.getRootVariableRegistry());
+        final ReloadComponent reloadComponent = statelessEngine.getReloadComponent();
+        final ExtensionManager extensionManager = statelessEngine.getExtensionManager();
+        final ValidationTrigger validationTrigger = statelessEngine.getValidationTrigger();
+        final ValidationContextFactory validationContextFactory = new StandardValidationContextFactory(controllerServiceProvider, componentVariableRegistry);
+
+        final ProcessorNode procNode = new StandardProcessorNode(loggableProcessor, identifier, validationContextFactory, processScheduler, controllerServiceProvider,
+            componentVariableRegistry, reloadComponent, extensionManager, validationTrigger);
+
+        logger.info("Created Processor of type {} with identifier {}", type, identifier);
+
+        return procNode;
+    }
+
+    public ReportingTaskNode buildReportingTask() throws ReportingTaskInstantiationException {
+        final LoggableComponent<ReportingTask> reportingTaskComponent = createLoggableReportingTask();
+        final ProcessScheduler processScheduler = statelessEngine.getProcessScheduler();
+        final ControllerServiceProvider controllerServiceProvider = statelessEngine.getControllerServiceProvider();
+        final ComponentVariableRegistry componentVariableRegistry = new StandardComponentVariableRegistry(statelessEngine.getRootVariableRegistry());
+        final ReloadComponent reloadComponent = statelessEngine.getReloadComponent();
+        final ExtensionManager extensionManager = statelessEngine.getExtensionManager();
+        final ValidationTrigger validationTrigger = statelessEngine.getValidationTrigger();
+        final ValidationContextFactory validationContextFactory = new StandardValidationContextFactory(controllerServiceProvider, componentVariableRegistry);
+
+        final ReportingTaskNode taskNode = new StatelessReportingTaskNode(reportingTaskComponent, identifier, statelessEngine, flowManager,
+            processScheduler, validationContextFactory, componentVariableRegistry, reloadComponent, extensionManager, validationTrigger);
+
+        logger.info("Created Reporting Task of type {} with identifier {}", type, identifier);
+        return taskNode;
+    }
+
+    private LoggableComponent<ReportingTask> createLoggableReportingTask() throws ReportingTaskInstantiationException {
+        try {
+            final LoggableComponent<ReportingTask> taskComponent = createLoggableComponent(ReportingTask.class);
+            final String taskName = taskComponent.getComponent().getClass().getSimpleName();
+            final NodeTypeProvider nodeTypeProvider = new StatelessNodeTypeProvider();
+
+            final ReportingInitializationContext config = new StandardReportingInitializationContext(identifier, taskName,
+                SchedulingStrategy.TIMER_DRIVEN, "1 min", taskComponent.getLogger(), statelessEngine.getControllerServiceProvider(),

Review comment:
       Declaring a static variable for the "1 min" duration would help clarify the reason for the selected duration.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/engine/StatelessProcessScheduler.java
##########
@@ -0,0 +1,285 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.engine;
+
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.components.validation.ValidationStatus;
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.connectable.Funnel;
+import org.apache.nifi.connectable.Port;
+import org.apache.nifi.controller.ProcessScheduler;
+import org.apache.nifi.controller.ProcessorNode;
+import org.apache.nifi.controller.ReportingTaskNode;
+import org.apache.nifi.controller.SchedulingAgentCallback;
+import org.apache.nifi.controller.scheduling.LifecycleState;
+import org.apache.nifi.controller.scheduling.SchedulingAgent;
+import org.apache.nifi.controller.service.ControllerServiceNode;
+import org.apache.nifi.engine.FlowEngine;
+import org.apache.nifi.nar.ExtensionManager;
+import org.apache.nifi.nar.NarCloseable;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.reporting.ReportingTask;
+import org.apache.nifi.scheduling.SchedulingStrategy;
+import org.apache.nifi.util.ReflectionUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+/**
+ * A ProcessScheduler that handles the lifecycle management of components but does not
+ * schedule the triggering of components.
+ */
+public class StatelessProcessScheduler implements ProcessScheduler {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessProcessScheduler.class);
+    private static final int ADMINISTRATIVE_YIELD_MILLIS = 1000;
+
+    private final SchedulingAgent schedulingAgent;
+    private final ExtensionManager extensionManager;
+
+    private FlowEngine componentLifeCycleThreadPool;
+    private ScheduledExecutorService componentMonitoringThreadPool;
+    private ProcessContextFactory processContextFactory;
+
+    public StatelessProcessScheduler(final ExtensionManager extensionManager) {
+        this.extensionManager = extensionManager;
+        schedulingAgent = new StatelessSchedulingAgent(extensionManager);
+    }
+
+    @Override
+    public void shutdown() {
+        if (componentLifeCycleThreadPool != null) {
+            componentLifeCycleThreadPool.shutdown();
+        }
+
+        if (componentMonitoringThreadPool != null) {
+            componentMonitoringThreadPool.shutdown();
+        }
+    }
+
+    public void initialize(final ProcessContextFactory processContextFactory) {
+        this.processContextFactory = processContextFactory;
+
+        componentLifeCycleThreadPool = new FlowEngine(8, "Component Lifecycle");
+        componentMonitoringThreadPool = new FlowEngine(2, "Monitor Processor Lifecycle", true);

Review comment:
       Recommend creating static variables for these two core pool sizes.  Was there a particular reason for selecting these pool sizes?

##########
File path: nifi-nar-bundles/nifi-standard-bundle/nifi-standard-reporting-tasks/src/main/java/org/apache/nifi/controller/ControllerStatusReportingTask.java
##########
@@ -117,25 +161,76 @@ public void onTrigger(final ReportingContext context) {
         builder.append(processorBorderLine);
         builder.append("\n");
 
-        printProcessorStatus(controllerStatus, builder, showDeltas);
+        printProcessorStatus(controllerStatus, builder, showDeltas, divisor);
 
         builder.append(processorBorderLine);
         processorLogger.info(builder.toString());
+    }
+
+    private void printConnectionStatuses(final ProcessGroupStatus controllerStatus, final boolean showDeltas, final long divisor) {
+        final StringBuilder builder = new StringBuilder();
 
-        builder.setLength(0);
         builder.append("Connection Statuses:\n");
         builder.append(connectionBorderLine);
         builder.append("\n");
         builder.append(connectionHeader);
         builder.append(connectionBorderLine);
         builder.append("\n");
 
-        printConnectionStatus(controllerStatus, builder, showDeltas);
+        printConnectionStatus(controllerStatus, builder, showDeltas, divisor);
 
         builder.append(connectionBorderLine);
         connectionLogger.info(builder.toString());
     }
 
+    private void printCounters(final ProcessGroupStatus controllerStatus, final boolean showDeltas, final long divisor) {
+        final StringBuilder builder = new StringBuilder();
+
+        builder.append("Counters:\n");
+        builder.append(counterBorderLine);
+        builder.append("\n");
+        builder.append(counterHeader);
+        builder.append(counterBorderLine);
+        builder.append("\n");
+
+        printCounterStatus(controllerStatus, builder, showDeltas, divisor);
+
+        builder.append(counterBorderLine);
+        counterLogger.info(builder.toString());
+    }
+
+    private void printCounterStatus(final ProcessGroupStatus status, final StringBuilder builder, final boolean showDeltas, final long divisor) {
+        final Collection<ProcessorStatus> processorStatuses = status.getProcessorStatus();
+        for (final ProcessorStatus processorStatus : processorStatuses) {
+            final Map<String, Long> counters = processorStatus.getCounters();
+
+            for (final Map.Entry<String, Long> entry : counters.entrySet()) {
+                final String counterName = entry.getKey();
+                final Long counterValue = entry.getValue() / divisor;
+
+                final String counterId = processorStatus.getId() + "_" + counterName;
+                final Long lastValue = lastCounterValues.getOrDefault(counterId, 0L);
+
+                lastCounterValues.put(counterId, counterValue);
+
+                if (showDeltas) {
+                    final String diff = toDiff(lastValue, counterValue);
+
+                    builder.append(String.format(COUNTER_LINE_FORMAT,
+                        processorStatus.getName() + "(" + processorStatus.getId() + ")",

Review comment:
       Since String.format() is being used, recommend incorporating the parentheses in the COUNTER_LINE_FORMAT definition to avoid the String concatenation.

##########
File path: nifi-system-tests/nifi-stateless-system-test-suite/src/test/java/org/apache/nifi/stateless/StatelessSystemIT.java
##########
@@ -0,0 +1,143 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.nifi.registry.flow.Bundle;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.stateless.bootstrap.StatelessBootstrap;
+import org.apache.nifi.stateless.config.ExtensionClientDefinition;
+import org.apache.nifi.stateless.config.ParameterContextDefinition;
+import org.apache.nifi.stateless.config.ReportingTaskDefinition;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.flow.DataflowDefinition;
+import org.apache.nifi.stateless.flow.StatelessDataflow;
+import org.junit.After;
+import org.junit.Before;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+
+public class StatelessSystemIT {
+    private final List<StatelessDataflow> createdFlows = new ArrayList<>();
+    protected static final Bundle SYSTEM_TEST_EXTENSIONS_BUNDLE = new Bundle("org.apache.nifi", "nifi-system-test-extensions-nar", "1.13.0");

Review comment:
       How will this version number be updated during releases?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/repository/StatelessRepositoryContextFactory.java
##########
@@ -0,0 +1,88 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.repository;
+
+import org.apache.nifi.connectable.Connectable;
+import org.apache.nifi.controller.repository.ContentRepository;
+import org.apache.nifi.controller.repository.CounterRepository;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.repository.FlowFileRepository;
+import org.apache.nifi.controller.repository.RepositoryContext;
+import org.apache.nifi.provenance.ProvenanceEventRepository;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicLong;
+
+public class StatelessRepositoryContextFactory implements RepositoryContextFactory {
+    private static final Logger logger = LoggerFactory.getLogger(StatelessRepositoryContextFactory.class);
+
+    private final ContentRepository contentRepository;
+    private final FlowFileRepository flowFileRepository;
+    private final FlowFileEventRepository flowFileEventRepository;
+    private final CounterRepository counterRepository;
+    private final ProvenanceEventRepository provenanceEventRepository;
+
+    public StatelessRepositoryContextFactory(final ContentRepository contentRepository, final FlowFileRepository flowFileRepository, final FlowFileEventRepository flowFileEventRepository,
+                                             final CounterRepository counterRepository, final ProvenanceEventRepository provenanceRepository) {
+        this.contentRepository = contentRepository;
+        this.flowFileRepository = flowFileRepository;
+        this.flowFileEventRepository = flowFileEventRepository;
+        this.counterRepository = counterRepository;
+        this.provenanceEventRepository = provenanceRepository;
+    }
+
+    @Override
+    public RepositoryContext createRepositoryContext(final Connectable connectable) {
+        return new StatelessRepositoryContext(connectable, new AtomicLong(0L), contentRepository, flowFileRepository, flowFileEventRepository, counterRepository, provenanceEventRepository);
+    }
+
+    @Override
+    public ContentRepository getContentRepository() {
+        return contentRepository;
+    }
+
+    @Override
+    public FlowFileEventRepository getFlowFileEventRepository() {
+        return flowFileEventRepository;
+    }
+
+    @Override
+    public void shutdown() {
+        contentRepository.shutdown();
+
+        try {
+            flowFileRepository.close();
+        } catch (final IOException e) {
+            logger.warn("Failed to properly shutdown FlowFIle Repository", e);

Review comment:
       The casing of FlowFile should be corrected

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/flow/StandardStatelessDataflowFactory.java
##########
@@ -0,0 +1,306 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.flow;
+
+import org.apache.nifi.components.state.HashMapStateProvider;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.state.StateProvider;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.repository.ContentRepository;
+import org.apache.nifi.controller.repository.CounterRepository;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.repository.FlowFileRepository;
+import org.apache.nifi.controller.repository.StandardCounterRepository;
+import org.apache.nifi.controller.repository.claim.ResourceClaimManager;
+import org.apache.nifi.controller.repository.claim.StandardResourceClaimManager;
+import org.apache.nifi.controller.repository.metrics.RingBufferEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.controller.service.StandardControllerServiceProvider;
+import org.apache.nifi.controller.state.manager.StandardStateManagerProvider;
+import org.apache.nifi.encrypt.StringEncryptor;
+import org.apache.nifi.events.EventReporter;
+import org.apache.nifi.events.VolatileBulletinRepository;
+import org.apache.nifi.extensions.ExtensionClient;
+import org.apache.nifi.extensions.ExtensionRepository;
+import org.apache.nifi.extensions.FileSystemExtensionRepository;
+import org.apache.nifi.extensions.NexusExtensionClient;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.nar.ExtensionDiscoveringManager;
+import org.apache.nifi.nar.NarClassLoaders;
+import org.apache.nifi.nar.NarClassLoadersHolder;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.parameter.StandardParameterContextManager;
+import org.apache.nifi.provenance.IdentifierLookup;
+import org.apache.nifi.provenance.ProvenanceRepository;
+import org.apache.nifi.provenance.VolatileProvenanceRepository;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.FlowRegistryClient;
+import org.apache.nifi.registry.flow.InMemoryFlowRegistry;
+import org.apache.nifi.registry.flow.StandardFlowRegistryClient;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.reporting.BulletinRepository;
+import org.apache.nifi.stateless.bootstrap.ExtensionDiscovery;
+import org.apache.nifi.stateless.config.ExtensionClientDefinition;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.SslConfigurationUtil;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.CachingProcessContextFactory;
+import org.apache.nifi.stateless.engine.ProcessContextFactory;
+import org.apache.nifi.stateless.engine.StandardStatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessAuthorizer;
+import org.apache.nifi.stateless.engine.StatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.engine.StatelessEngineInitializationContext;
+import org.apache.nifi.stateless.engine.StatelessFlowManager;
+import org.apache.nifi.stateless.engine.StatelessProcessContextFactory;
+import org.apache.nifi.stateless.engine.StatelessProcessScheduler;
+import org.apache.nifi.stateless.engine.StatelessProvenanceAuthorizableFactory;
+import org.apache.nifi.stateless.repository.ByteArrayContentRepository;
+import org.apache.nifi.stateless.repository.RepositoryContextFactory;
+import org.apache.nifi.stateless.repository.StatelessFlowFileRepository;
+import org.apache.nifi.stateless.repository.StatelessRepositoryContextFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.ArrayList;
+import java.util.List;
+
+public class StandardStatelessDataflowFactory implements StatelessDataflowFactory<VersionedFlowSnapshot> {
+    private static final Logger logger = LoggerFactory.getLogger(StandardStatelessDataflowFactory.class);
+
+    @Override
+    public StatelessDataflow createDataflow(final StatelessEngineConfiguration engineConfiguration, final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition,
+                                            final List<ParameterOverride> parameterOverrides) throws IOException, StatelessConfigurationException {
+        final long start = System.currentTimeMillis();
+
+        final VersionedFlowSnapshot flowSnapshot = dataflowDefinition.getFlowSnapshot();
+
+        ProvenanceRepository provenanceRepo = null;
+        ContentRepository contentRepo = null;
+        StatelessProcessScheduler processScheduler = null;
+        FlowFileRepository flowFileRepo = null;
+        FlowFileEventRepository flowFileEventRepo = null;
+
+        try {
+            final BulletinRepository bulletinRepository = new VolatileBulletinRepository();
+            final File workingDir = engineConfiguration.getWorkingDirectory();
+            if (!workingDir.exists() && !workingDir.mkdirs()) {
+                throw new IOException("Working Directory " + workingDir + " does not exist and could not be created");
+            }
+
+            final InMemoryFlowRegistry flowRegistry = new InMemoryFlowRegistry();
+            flowRegistry.addFlowSnapshot(flowSnapshot);
+            final FlowRegistryClient flowRegistryClient = new StandardFlowRegistryClient();
+            flowRegistryClient.addFlowRegistry(flowRegistry);
+
+            final File extensionsWorkingDir = new File(workingDir, "extensions");
+            final ClassLoader systemClassLoader = createSystemClassLoader(engineConfiguration.getNarDirectory());
+            final ExtensionDiscoveringManager extensionManager = ExtensionDiscovery.discover(extensionsWorkingDir, systemClassLoader);
+
+            flowFileEventRepo = new RingBufferEventRepository(5);
+
+            final StateProvider stateProvider = new HashMapStateProvider();
+            final StateManagerProvider stateManagerProvider = new StandardStateManagerProvider(stateProvider, stateProvider);
+
+            final ParameterContextManager parameterContextManager = new StandardParameterContextManager();
+            processScheduler = new StatelessProcessScheduler(extensionManager);
+            provenanceRepo = new VolatileProvenanceRepository(1_000, "", "");
+            provenanceRepo.initialize(EventReporter.NO_OP, new StatelessAuthorizer(), new StatelessProvenanceAuthorizableFactory(), IdentifierLookup.EMPTY);
+
+            final SSLContext sslContext;
+            try {
+                sslContext = SslConfigurationUtil.createSslContext(engineConfiguration.getSslContext());
+            } catch (StatelessConfigurationException e) {
+                throw new StatelessConfigurationException("Could not create SSLContext", e);
+            }
+
+            // Build Extension Repository
+            final NarClassLoaders narClassLoaders = NarClassLoadersHolder.getInstance();
+            final List<ExtensionClient> extensionClients = new ArrayList<>();
+            for (final ExtensionClientDefinition extensionClientDefinition : engineConfiguration.getExtensionClients()) {
+                final ExtensionClient extensionClient = createExtensionClient(extensionClientDefinition, engineConfiguration.getSslContext());
+                extensionClients.add(extensionClient);
+            }
+
+            final ExtensionRepository extensionRepository = new FileSystemExtensionRepository(extensionManager, engineConfiguration.getNarDirectory(), engineConfiguration.getWorkingDirectory(),
+                narClassLoaders, extensionClients);
+
+            final VariableRegistry variableRegistry = VariableRegistry.EMPTY_REGISTRY;
+            final StringEncryptor encryptor = StringEncryptor.createEncryptor("PBEWITHMD5AND256BITAES-CBC-OPENSSL", "BC", engineConfiguration.getSensitivePropsKey());
+
+            final File krb5File = engineConfiguration.getKrb5File();
+            final KerberosConfig kerberosConfig = new KerberosConfig(null, null, krb5File);
+            logger.info("Setting java.security.krb5.conf to {}", krb5File.getAbsolutePath());
+            System.setProperty("java.security.krb5.conf", krb5File.getAbsolutePath());
+
+            final StatelessEngine<VersionedFlowSnapshot> statelessEngine = new StandardStatelessEngine.Builder()
+                .bulletinRepository(bulletinRepository)
+                .encryptor(encryptor)
+                .extensionManager(extensionManager)
+                .flowRegistryClient(flowRegistryClient)
+                .stateManagerProvider(stateManagerProvider)
+                .variableRegistry(variableRegistry)
+                .processScheduler(processScheduler)
+                .kerberosConfiguration(kerberosConfig)
+                .flowFileEventRepository(flowFileEventRepo)
+                .provenanceRepository(provenanceRepo)
+                .extensionRepository(extensionRepository)
+                .build();
+
+            final StatelessFlowManager flowManager = new StatelessFlowManager(flowFileEventRepo, parameterContextManager, statelessEngine, () -> true, sslContext);
+            final ControllerServiceProvider controllerServiceProvider = new StandardControllerServiceProvider(processScheduler, bulletinRepository, flowManager, extensionManager);
+
+            final ProcessContextFactory rawProcessContextFactory = new StatelessProcessContextFactory(controllerServiceProvider, encryptor, stateManagerProvider);
+            final ProcessContextFactory processContextFactory = new CachingProcessContextFactory(rawProcessContextFactory);
+            contentRepo = new ByteArrayContentRepository();
+            flowFileRepo = new StatelessFlowFileRepository();
+            final CounterRepository counterRepo = new StandardCounterRepository();
+
+            final RepositoryContextFactory repositoryContextFactory = new StatelessRepositoryContextFactory(contentRepo, flowFileRepo, flowFileEventRepo, counterRepo, provenanceRepo);
+            final StatelessEngineInitializationContext statelessEngineInitializationContext = new StatelessEngineInitializationContext(controllerServiceProvider, flowManager, processContextFactory,
+                repositoryContextFactory);
+
+            processScheduler.initialize(processContextFactory);
+            statelessEngine.initialize(statelessEngineInitializationContext);
+
+            // Initialize components. This is generally needed because of the interdependencies between the components.
+            // There are some circular dependencies that are resolved by passing objects via initialization rather than by providing to the constructors.
+            final ResourceClaimManager resourceClaimManager = new StandardResourceClaimManager();
+            contentRepo.initialize(resourceClaimManager);
+            flowFileRepo.initialize(resourceClaimManager);
+            flowManager.initialize(controllerServiceProvider);
+
+            // Create flow
+            final ProcessGroup rootGroup = flowManager.createProcessGroup("root");
+            rootGroup.setName("root");
+            flowManager.setRootGroup(rootGroup);
+
+            final StatelessDataflow dataflow = statelessEngine.createFlow(dataflowDefinition, parameterOverrides);
+            final long millis = System.currentTimeMillis() - start;
+            logger.info("NiFi Stateless Engine and Dataflow created and initialized in {} millis", millis);
+
+            return dataflow;
+        } catch (final Exception e) {
+            try {
+                if (provenanceRepo != null) {
+                    provenanceRepo.close();
+                }
+            } catch (final IOException ioe) {
+                e.addSuppressed(ioe);
+            }
+
+            if (contentRepo != null) {
+                contentRepo.shutdown();
+            }
+
+            if (processScheduler != null) {
+                processScheduler.shutdown();
+            }
+
+            if (flowFileRepo != null) {
+                try {
+                    flowFileRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            if (flowFileEventRepo != null) {
+                try {
+                    flowFileEventRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            throw e;
+        }
+    }
+
+    private ExtensionClient createExtensionClient(final ExtensionClientDefinition definition, final SslContextDefinition sslContextDefinition) {
+        final String type = definition.getExtensionClientType();
+        if (!"nexus".equalsIgnoreCase(type.trim())) {
+            throw new IllegalArgumentException("Invalid Extension Client type: <" + definition.getExtensionClientType() +">. Currently, the only supported type is <nexus>");
+        }
+
+        final SslContextDefinition sslContext = (definition.isUseSslContext() && sslContextDefinition != null) ? sslContextDefinition : null;
+        return new NexusExtensionClient(definition.getBaseUrl(), sslContext, definition.getCommsTimeout());
+    }
+
+    private ClassLoader createSystemClassLoader(final File narDirectory) throws StatelessConfigurationException {
+        final ClassLoader systemClassLoader = StatelessDataflowFactory.class.getClassLoader();
+        final int javaMajorVersion = getJavaMajorVersion();
+        if (javaMajorVersion >= 11) {
+            // If running on Java 11 or greater, add the JAXB/activation/annotation libs to the classpath.
+            // TODO: Once the minimum Java version requirement of NiFi is 11, this processing should be removed.
+            // JAXB/activation/annotation will be added as an actual dependency via pom.xml.
+            return createJava11OrLaterSystemClassLoader(javaMajorVersion, narDirectory, systemClassLoader);
+        }
+
+        return systemClassLoader;
+    }
+
+    private ClassLoader createJava11OrLaterSystemClassLoader(final int javaMajorVersion, final File narDirectory, final ClassLoader parentClassLoader) throws StatelessConfigurationException {
+        final List<URL> java11JarFileUrls = new ArrayList<>();
+
+        final File java11Dir = new File(narDirectory, "java11");

Review comment:
       Should this directory be named something other than java11 since the libraries are required for Java 11 and higher?  Referencing the reason for the change, perhaps naming the directory jep-320 or or java-ee would be an option?

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/queue/StatelessFlowFileQueue.java
##########
@@ -0,0 +1,349 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.queue;
+
+import org.apache.nifi.controller.queue.DropFlowFileStatus;
+import org.apache.nifi.controller.queue.ListFlowFileStatus;
+import org.apache.nifi.controller.queue.LoadBalanceCompression;
+import org.apache.nifi.controller.queue.LoadBalanceStrategy;
+import org.apache.nifi.controller.queue.QueueDiagnostics;
+import org.apache.nifi.controller.queue.QueueSize;
+import org.apache.nifi.controller.repository.FlowFileRecord;
+import org.apache.nifi.controller.repository.SwapSummary;
+import org.apache.nifi.flowfile.FlowFilePrioritizer;
+import org.apache.nifi.processor.FlowFileFilter;
+import org.apache.nifi.util.FormatUtils;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class StatelessFlowFileQueue implements DrainableFlowFileQueue {
+    private final String identifier;
+    private volatile long expirationMillis;
+    private final BlockingQueue<FlowFileRecord> flowFiles = new LinkedBlockingQueue<>();
+    private final AtomicInteger unacknowledgedCount = new AtomicInteger(0);
+
+    public StatelessFlowFileQueue(final String identifier) {
+        this.identifier = identifier;
+    }
+
+    @Override
+    public String getIdentifier() {
+        return identifier;
+    }
+
+    @Override
+    public List<FlowFilePrioritizer> getPriorities() {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public SwapSummary recoverSwappedFlowFiles() {
+        return null;
+    }
+
+    @Override
+    public void purgeSwapFiles() {
+    }
+
+    @Override
+    public void setPriorities(final List<FlowFilePrioritizer> newPriorities) {
+    }
+
+    @Override
+    public void setBackPressureObjectThreshold(final long maxQueueSize) {
+    }
+
+    @Override
+    public long getBackPressureObjectThreshold() {
+        return 0;
+    }
+
+    @Override
+    public void setBackPressureDataSizeThreshold(final String maxDataSize) {
+    }
+
+    @Override
+    public String getBackPressureDataSizeThreshold() {
+        return "0 B";
+    }
+
+    @Override
+    public QueueSize size() {
+        return new QueueSize(flowFiles.size() + unacknowledgedCount.get(), 0);
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return flowFiles.isEmpty() && unacknowledgedCount.get() == 0;
+    }
+
+    @Override
+    public boolean isActiveQueueEmpty() {
+        return flowFiles.isEmpty();
+    }
+
+    @Override
+    public void acknowledge(final FlowFileRecord flowFile) {
+        unacknowledgedCount.decrementAndGet();
+    }
+
+    @Override
+    public void acknowledge(final Collection<FlowFileRecord> flowFiles) {
+        unacknowledgedCount.addAndGet(-flowFiles.size());
+    }
+
+    @Override
+    public boolean isUnacknowledgedFlowFile() {
+        return unacknowledgedCount.get() > 0;
+    }
+
+    @Override
+    public boolean isFull() {
+        return false;
+    }
+
+    @Override
+    public void put(final FlowFileRecord flowFile) {
+        flowFiles.add(flowFile);
+    }
+
+    @Override
+    public void putAll(final Collection<FlowFileRecord> flowFiles) {
+        this.flowFiles.addAll(flowFiles);
+    }
+
+    @Override
+    public synchronized FlowFileRecord poll(final Set<FlowFileRecord> expiredRecords) {
+        while (!flowFiles.isEmpty()) {
+            final FlowFileRecord flowFile = flowFiles.peek();
+            if (flowFile == null) {
+                return null;
+            }
+
+            if (isExpired(flowFile)) {
+                expiredRecords.add(flowFile);
+                if (expiredRecords.size() >= 10_000) {

Review comment:
       Is there a particular reason for checking the size at 10_000?  Recommend replacing this and other references in the file with a static class variable that helps indicate the reason for the particular value.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/flow/StandardStatelessDataflowFactory.java
##########
@@ -0,0 +1,306 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.flow;
+
+import org.apache.nifi.components.state.HashMapStateProvider;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.state.StateProvider;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.repository.ContentRepository;
+import org.apache.nifi.controller.repository.CounterRepository;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.repository.FlowFileRepository;
+import org.apache.nifi.controller.repository.StandardCounterRepository;
+import org.apache.nifi.controller.repository.claim.ResourceClaimManager;
+import org.apache.nifi.controller.repository.claim.StandardResourceClaimManager;
+import org.apache.nifi.controller.repository.metrics.RingBufferEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.controller.service.StandardControllerServiceProvider;
+import org.apache.nifi.controller.state.manager.StandardStateManagerProvider;
+import org.apache.nifi.encrypt.StringEncryptor;
+import org.apache.nifi.events.EventReporter;
+import org.apache.nifi.events.VolatileBulletinRepository;
+import org.apache.nifi.extensions.ExtensionClient;
+import org.apache.nifi.extensions.ExtensionRepository;
+import org.apache.nifi.extensions.FileSystemExtensionRepository;
+import org.apache.nifi.extensions.NexusExtensionClient;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.nar.ExtensionDiscoveringManager;
+import org.apache.nifi.nar.NarClassLoaders;
+import org.apache.nifi.nar.NarClassLoadersHolder;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.parameter.StandardParameterContextManager;
+import org.apache.nifi.provenance.IdentifierLookup;
+import org.apache.nifi.provenance.ProvenanceRepository;
+import org.apache.nifi.provenance.VolatileProvenanceRepository;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.FlowRegistryClient;
+import org.apache.nifi.registry.flow.InMemoryFlowRegistry;
+import org.apache.nifi.registry.flow.StandardFlowRegistryClient;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.reporting.BulletinRepository;
+import org.apache.nifi.stateless.bootstrap.ExtensionDiscovery;
+import org.apache.nifi.stateless.config.ExtensionClientDefinition;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.SslConfigurationUtil;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.CachingProcessContextFactory;
+import org.apache.nifi.stateless.engine.ProcessContextFactory;
+import org.apache.nifi.stateless.engine.StandardStatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessAuthorizer;
+import org.apache.nifi.stateless.engine.StatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.engine.StatelessEngineInitializationContext;
+import org.apache.nifi.stateless.engine.StatelessFlowManager;
+import org.apache.nifi.stateless.engine.StatelessProcessContextFactory;
+import org.apache.nifi.stateless.engine.StatelessProcessScheduler;
+import org.apache.nifi.stateless.engine.StatelessProvenanceAuthorizableFactory;
+import org.apache.nifi.stateless.repository.ByteArrayContentRepository;
+import org.apache.nifi.stateless.repository.RepositoryContextFactory;
+import org.apache.nifi.stateless.repository.StatelessFlowFileRepository;
+import org.apache.nifi.stateless.repository.StatelessRepositoryContextFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.ArrayList;
+import java.util.List;
+
+public class StandardStatelessDataflowFactory implements StatelessDataflowFactory<VersionedFlowSnapshot> {
+    private static final Logger logger = LoggerFactory.getLogger(StandardStatelessDataflowFactory.class);
+
+    @Override
+    public StatelessDataflow createDataflow(final StatelessEngineConfiguration engineConfiguration, final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition,
+                                            final List<ParameterOverride> parameterOverrides) throws IOException, StatelessConfigurationException {
+        final long start = System.currentTimeMillis();
+
+        final VersionedFlowSnapshot flowSnapshot = dataflowDefinition.getFlowSnapshot();
+
+        ProvenanceRepository provenanceRepo = null;
+        ContentRepository contentRepo = null;
+        StatelessProcessScheduler processScheduler = null;
+        FlowFileRepository flowFileRepo = null;
+        FlowFileEventRepository flowFileEventRepo = null;
+
+        try {
+            final BulletinRepository bulletinRepository = new VolatileBulletinRepository();
+            final File workingDir = engineConfiguration.getWorkingDirectory();
+            if (!workingDir.exists() && !workingDir.mkdirs()) {
+                throw new IOException("Working Directory " + workingDir + " does not exist and could not be created");
+            }
+
+            final InMemoryFlowRegistry flowRegistry = new InMemoryFlowRegistry();
+            flowRegistry.addFlowSnapshot(flowSnapshot);
+            final FlowRegistryClient flowRegistryClient = new StandardFlowRegistryClient();
+            flowRegistryClient.addFlowRegistry(flowRegistry);
+
+            final File extensionsWorkingDir = new File(workingDir, "extensions");
+            final ClassLoader systemClassLoader = createSystemClassLoader(engineConfiguration.getNarDirectory());
+            final ExtensionDiscoveringManager extensionManager = ExtensionDiscovery.discover(extensionsWorkingDir, systemClassLoader);
+
+            flowFileEventRepo = new RingBufferEventRepository(5);
+
+            final StateProvider stateProvider = new HashMapStateProvider();
+            final StateManagerProvider stateManagerProvider = new StandardStateManagerProvider(stateProvider, stateProvider);
+
+            final ParameterContextManager parameterContextManager = new StandardParameterContextManager();
+            processScheduler = new StatelessProcessScheduler(extensionManager);
+            provenanceRepo = new VolatileProvenanceRepository(1_000, "", "");
+            provenanceRepo.initialize(EventReporter.NO_OP, new StatelessAuthorizer(), new StatelessProvenanceAuthorizableFactory(), IdentifierLookup.EMPTY);
+
+            final SSLContext sslContext;
+            try {
+                sslContext = SslConfigurationUtil.createSslContext(engineConfiguration.getSslContext());
+            } catch (StatelessConfigurationException e) {
+                throw new StatelessConfigurationException("Could not create SSLContext", e);
+            }
+
+            // Build Extension Repository
+            final NarClassLoaders narClassLoaders = NarClassLoadersHolder.getInstance();
+            final List<ExtensionClient> extensionClients = new ArrayList<>();
+            for (final ExtensionClientDefinition extensionClientDefinition : engineConfiguration.getExtensionClients()) {
+                final ExtensionClient extensionClient = createExtensionClient(extensionClientDefinition, engineConfiguration.getSslContext());
+                extensionClients.add(extensionClient);
+            }
+
+            final ExtensionRepository extensionRepository = new FileSystemExtensionRepository(extensionManager, engineConfiguration.getNarDirectory(), engineConfiguration.getWorkingDirectory(),
+                narClassLoaders, extensionClients);
+
+            final VariableRegistry variableRegistry = VariableRegistry.EMPTY_REGISTRY;
+            final StringEncryptor encryptor = StringEncryptor.createEncryptor("PBEWITHMD5AND256BITAES-CBC-OPENSSL", "BC", engineConfiguration.getSensitivePropsKey());

Review comment:
       Recommend making the algorithm a configurable option or at least promoting the setting to a static class variable for documentation purposes.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/flow/StandardStatelessDataflowFactory.java
##########
@@ -0,0 +1,306 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.flow;
+
+import org.apache.nifi.components.state.HashMapStateProvider;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.state.StateProvider;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.repository.ContentRepository;
+import org.apache.nifi.controller.repository.CounterRepository;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.repository.FlowFileRepository;
+import org.apache.nifi.controller.repository.StandardCounterRepository;
+import org.apache.nifi.controller.repository.claim.ResourceClaimManager;
+import org.apache.nifi.controller.repository.claim.StandardResourceClaimManager;
+import org.apache.nifi.controller.repository.metrics.RingBufferEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.controller.service.StandardControllerServiceProvider;
+import org.apache.nifi.controller.state.manager.StandardStateManagerProvider;
+import org.apache.nifi.encrypt.StringEncryptor;
+import org.apache.nifi.events.EventReporter;
+import org.apache.nifi.events.VolatileBulletinRepository;
+import org.apache.nifi.extensions.ExtensionClient;
+import org.apache.nifi.extensions.ExtensionRepository;
+import org.apache.nifi.extensions.FileSystemExtensionRepository;
+import org.apache.nifi.extensions.NexusExtensionClient;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.nar.ExtensionDiscoveringManager;
+import org.apache.nifi.nar.NarClassLoaders;
+import org.apache.nifi.nar.NarClassLoadersHolder;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.parameter.StandardParameterContextManager;
+import org.apache.nifi.provenance.IdentifierLookup;
+import org.apache.nifi.provenance.ProvenanceRepository;
+import org.apache.nifi.provenance.VolatileProvenanceRepository;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.FlowRegistryClient;
+import org.apache.nifi.registry.flow.InMemoryFlowRegistry;
+import org.apache.nifi.registry.flow.StandardFlowRegistryClient;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.reporting.BulletinRepository;
+import org.apache.nifi.stateless.bootstrap.ExtensionDiscovery;
+import org.apache.nifi.stateless.config.ExtensionClientDefinition;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.SslConfigurationUtil;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.CachingProcessContextFactory;
+import org.apache.nifi.stateless.engine.ProcessContextFactory;
+import org.apache.nifi.stateless.engine.StandardStatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessAuthorizer;
+import org.apache.nifi.stateless.engine.StatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.engine.StatelessEngineInitializationContext;
+import org.apache.nifi.stateless.engine.StatelessFlowManager;
+import org.apache.nifi.stateless.engine.StatelessProcessContextFactory;
+import org.apache.nifi.stateless.engine.StatelessProcessScheduler;
+import org.apache.nifi.stateless.engine.StatelessProvenanceAuthorizableFactory;
+import org.apache.nifi.stateless.repository.ByteArrayContentRepository;
+import org.apache.nifi.stateless.repository.RepositoryContextFactory;
+import org.apache.nifi.stateless.repository.StatelessFlowFileRepository;
+import org.apache.nifi.stateless.repository.StatelessRepositoryContextFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.ArrayList;
+import java.util.List;
+
+public class StandardStatelessDataflowFactory implements StatelessDataflowFactory<VersionedFlowSnapshot> {
+    private static final Logger logger = LoggerFactory.getLogger(StandardStatelessDataflowFactory.class);
+
+    @Override
+    public StatelessDataflow createDataflow(final StatelessEngineConfiguration engineConfiguration, final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition,
+                                            final List<ParameterOverride> parameterOverrides) throws IOException, StatelessConfigurationException {
+        final long start = System.currentTimeMillis();
+
+        final VersionedFlowSnapshot flowSnapshot = dataflowDefinition.getFlowSnapshot();
+
+        ProvenanceRepository provenanceRepo = null;
+        ContentRepository contentRepo = null;
+        StatelessProcessScheduler processScheduler = null;
+        FlowFileRepository flowFileRepo = null;
+        FlowFileEventRepository flowFileEventRepo = null;
+
+        try {
+            final BulletinRepository bulletinRepository = new VolatileBulletinRepository();
+            final File workingDir = engineConfiguration.getWorkingDirectory();
+            if (!workingDir.exists() && !workingDir.mkdirs()) {
+                throw new IOException("Working Directory " + workingDir + " does not exist and could not be created");
+            }
+
+            final InMemoryFlowRegistry flowRegistry = new InMemoryFlowRegistry();
+            flowRegistry.addFlowSnapshot(flowSnapshot);
+            final FlowRegistryClient flowRegistryClient = new StandardFlowRegistryClient();
+            flowRegistryClient.addFlowRegistry(flowRegistry);
+
+            final File extensionsWorkingDir = new File(workingDir, "extensions");
+            final ClassLoader systemClassLoader = createSystemClassLoader(engineConfiguration.getNarDirectory());
+            final ExtensionDiscoveringManager extensionManager = ExtensionDiscovery.discover(extensionsWorkingDir, systemClassLoader);
+
+            flowFileEventRepo = new RingBufferEventRepository(5);
+
+            final StateProvider stateProvider = new HashMapStateProvider();
+            final StateManagerProvider stateManagerProvider = new StandardStateManagerProvider(stateProvider, stateProvider);
+
+            final ParameterContextManager parameterContextManager = new StandardParameterContextManager();
+            processScheduler = new StatelessProcessScheduler(extensionManager);
+            provenanceRepo = new VolatileProvenanceRepository(1_000, "", "");
+            provenanceRepo.initialize(EventReporter.NO_OP, new StatelessAuthorizer(), new StatelessProvenanceAuthorizableFactory(), IdentifierLookup.EMPTY);
+
+            final SSLContext sslContext;
+            try {
+                sslContext = SslConfigurationUtil.createSslContext(engineConfiguration.getSslContext());
+            } catch (StatelessConfigurationException e) {
+                throw new StatelessConfigurationException("Could not create SSLContext", e);
+            }
+
+            // Build Extension Repository
+            final NarClassLoaders narClassLoaders = NarClassLoadersHolder.getInstance();
+            final List<ExtensionClient> extensionClients = new ArrayList<>();
+            for (final ExtensionClientDefinition extensionClientDefinition : engineConfiguration.getExtensionClients()) {
+                final ExtensionClient extensionClient = createExtensionClient(extensionClientDefinition, engineConfiguration.getSslContext());
+                extensionClients.add(extensionClient);
+            }
+
+            final ExtensionRepository extensionRepository = new FileSystemExtensionRepository(extensionManager, engineConfiguration.getNarDirectory(), engineConfiguration.getWorkingDirectory(),
+                narClassLoaders, extensionClients);
+
+            final VariableRegistry variableRegistry = VariableRegistry.EMPTY_REGISTRY;
+            final StringEncryptor encryptor = StringEncryptor.createEncryptor("PBEWITHMD5AND256BITAES-CBC-OPENSSL", "BC", engineConfiguration.getSensitivePropsKey());
+
+            final File krb5File = engineConfiguration.getKrb5File();
+            final KerberosConfig kerberosConfig = new KerberosConfig(null, null, krb5File);
+            logger.info("Setting java.security.krb5.conf to {}", krb5File.getAbsolutePath());
+            System.setProperty("java.security.krb5.conf", krb5File.getAbsolutePath());
+
+            final StatelessEngine<VersionedFlowSnapshot> statelessEngine = new StandardStatelessEngine.Builder()
+                .bulletinRepository(bulletinRepository)
+                .encryptor(encryptor)
+                .extensionManager(extensionManager)
+                .flowRegistryClient(flowRegistryClient)
+                .stateManagerProvider(stateManagerProvider)
+                .variableRegistry(variableRegistry)
+                .processScheduler(processScheduler)
+                .kerberosConfiguration(kerberosConfig)
+                .flowFileEventRepository(flowFileEventRepo)
+                .provenanceRepository(provenanceRepo)
+                .extensionRepository(extensionRepository)
+                .build();
+
+            final StatelessFlowManager flowManager = new StatelessFlowManager(flowFileEventRepo, parameterContextManager, statelessEngine, () -> true, sslContext);
+            final ControllerServiceProvider controllerServiceProvider = new StandardControllerServiceProvider(processScheduler, bulletinRepository, flowManager, extensionManager);
+
+            final ProcessContextFactory rawProcessContextFactory = new StatelessProcessContextFactory(controllerServiceProvider, encryptor, stateManagerProvider);
+            final ProcessContextFactory processContextFactory = new CachingProcessContextFactory(rawProcessContextFactory);
+            contentRepo = new ByteArrayContentRepository();
+            flowFileRepo = new StatelessFlowFileRepository();
+            final CounterRepository counterRepo = new StandardCounterRepository();
+
+            final RepositoryContextFactory repositoryContextFactory = new StatelessRepositoryContextFactory(contentRepo, flowFileRepo, flowFileEventRepo, counterRepo, provenanceRepo);
+            final StatelessEngineInitializationContext statelessEngineInitializationContext = new StatelessEngineInitializationContext(controllerServiceProvider, flowManager, processContextFactory,
+                repositoryContextFactory);
+
+            processScheduler.initialize(processContextFactory);
+            statelessEngine.initialize(statelessEngineInitializationContext);
+
+            // Initialize components. This is generally needed because of the interdependencies between the components.
+            // There are some circular dependencies that are resolved by passing objects via initialization rather than by providing to the constructors.
+            final ResourceClaimManager resourceClaimManager = new StandardResourceClaimManager();
+            contentRepo.initialize(resourceClaimManager);
+            flowFileRepo.initialize(resourceClaimManager);
+            flowManager.initialize(controllerServiceProvider);
+
+            // Create flow
+            final ProcessGroup rootGroup = flowManager.createProcessGroup("root");
+            rootGroup.setName("root");
+            flowManager.setRootGroup(rootGroup);
+
+            final StatelessDataflow dataflow = statelessEngine.createFlow(dataflowDefinition, parameterOverrides);
+            final long millis = System.currentTimeMillis() - start;
+            logger.info("NiFi Stateless Engine and Dataflow created and initialized in {} millis", millis);
+
+            return dataflow;
+        } catch (final Exception e) {
+            try {
+                if (provenanceRepo != null) {
+                    provenanceRepo.close();
+                }
+            } catch (final IOException ioe) {
+                e.addSuppressed(ioe);
+            }
+
+            if (contentRepo != null) {
+                contentRepo.shutdown();
+            }
+
+            if (processScheduler != null) {
+                processScheduler.shutdown();
+            }
+
+            if (flowFileRepo != null) {
+                try {
+                    flowFileRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            if (flowFileEventRepo != null) {
+                try {
+                    flowFileEventRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            throw e;
+        }
+    }
+
+    private ExtensionClient createExtensionClient(final ExtensionClientDefinition definition, final SslContextDefinition sslContextDefinition) {
+        final String type = definition.getExtensionClientType();
+        if (!"nexus".equalsIgnoreCase(type.trim())) {

Review comment:
       Although it is a simple check, creating a separate method named something like isValidExtensionClientType() would help add some context to this element of validation.

##########
File path: nifi-nar-bundles/nifi-framework-bundle/nifi-stateless-bundle/nifi-stateless-engine/src/main/java/org/apache/nifi/stateless/flow/StandardStatelessDataflowFactory.java
##########
@@ -0,0 +1,306 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.nifi.stateless.flow;
+
+import org.apache.nifi.components.state.HashMapStateProvider;
+import org.apache.nifi.components.state.StateManagerProvider;
+import org.apache.nifi.components.state.StateProvider;
+import org.apache.nifi.controller.kerberos.KerberosConfig;
+import org.apache.nifi.controller.repository.ContentRepository;
+import org.apache.nifi.controller.repository.CounterRepository;
+import org.apache.nifi.controller.repository.FlowFileEventRepository;
+import org.apache.nifi.controller.repository.FlowFileRepository;
+import org.apache.nifi.controller.repository.StandardCounterRepository;
+import org.apache.nifi.controller.repository.claim.ResourceClaimManager;
+import org.apache.nifi.controller.repository.claim.StandardResourceClaimManager;
+import org.apache.nifi.controller.repository.metrics.RingBufferEventRepository;
+import org.apache.nifi.controller.service.ControllerServiceProvider;
+import org.apache.nifi.controller.service.StandardControllerServiceProvider;
+import org.apache.nifi.controller.state.manager.StandardStateManagerProvider;
+import org.apache.nifi.encrypt.StringEncryptor;
+import org.apache.nifi.events.EventReporter;
+import org.apache.nifi.events.VolatileBulletinRepository;
+import org.apache.nifi.extensions.ExtensionClient;
+import org.apache.nifi.extensions.ExtensionRepository;
+import org.apache.nifi.extensions.FileSystemExtensionRepository;
+import org.apache.nifi.extensions.NexusExtensionClient;
+import org.apache.nifi.groups.ProcessGroup;
+import org.apache.nifi.nar.ExtensionDiscoveringManager;
+import org.apache.nifi.nar.NarClassLoaders;
+import org.apache.nifi.nar.NarClassLoadersHolder;
+import org.apache.nifi.parameter.ParameterContextManager;
+import org.apache.nifi.parameter.StandardParameterContextManager;
+import org.apache.nifi.provenance.IdentifierLookup;
+import org.apache.nifi.provenance.ProvenanceRepository;
+import org.apache.nifi.provenance.VolatileProvenanceRepository;
+import org.apache.nifi.registry.VariableRegistry;
+import org.apache.nifi.registry.flow.FlowRegistryClient;
+import org.apache.nifi.registry.flow.InMemoryFlowRegistry;
+import org.apache.nifi.registry.flow.StandardFlowRegistryClient;
+import org.apache.nifi.registry.flow.VersionedFlowSnapshot;
+import org.apache.nifi.reporting.BulletinRepository;
+import org.apache.nifi.stateless.bootstrap.ExtensionDiscovery;
+import org.apache.nifi.stateless.config.ExtensionClientDefinition;
+import org.apache.nifi.stateless.config.ParameterOverride;
+import org.apache.nifi.stateless.config.SslConfigurationUtil;
+import org.apache.nifi.stateless.config.SslContextDefinition;
+import org.apache.nifi.stateless.config.StatelessConfigurationException;
+import org.apache.nifi.stateless.engine.CachingProcessContextFactory;
+import org.apache.nifi.stateless.engine.ProcessContextFactory;
+import org.apache.nifi.stateless.engine.StandardStatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessAuthorizer;
+import org.apache.nifi.stateless.engine.StatelessEngine;
+import org.apache.nifi.stateless.engine.StatelessEngineConfiguration;
+import org.apache.nifi.stateless.engine.StatelessEngineInitializationContext;
+import org.apache.nifi.stateless.engine.StatelessFlowManager;
+import org.apache.nifi.stateless.engine.StatelessProcessContextFactory;
+import org.apache.nifi.stateless.engine.StatelessProcessScheduler;
+import org.apache.nifi.stateless.engine.StatelessProvenanceAuthorizableFactory;
+import org.apache.nifi.stateless.repository.ByteArrayContentRepository;
+import org.apache.nifi.stateless.repository.RepositoryContextFactory;
+import org.apache.nifi.stateless.repository.StatelessFlowFileRepository;
+import org.apache.nifi.stateless.repository.StatelessRepositoryContextFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLContext;
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.ArrayList;
+import java.util.List;
+
+public class StandardStatelessDataflowFactory implements StatelessDataflowFactory<VersionedFlowSnapshot> {
+    private static final Logger logger = LoggerFactory.getLogger(StandardStatelessDataflowFactory.class);
+
+    @Override
+    public StatelessDataflow createDataflow(final StatelessEngineConfiguration engineConfiguration, final DataflowDefinition<VersionedFlowSnapshot> dataflowDefinition,
+                                            final List<ParameterOverride> parameterOverrides) throws IOException, StatelessConfigurationException {
+        final long start = System.currentTimeMillis();
+
+        final VersionedFlowSnapshot flowSnapshot = dataflowDefinition.getFlowSnapshot();
+
+        ProvenanceRepository provenanceRepo = null;
+        ContentRepository contentRepo = null;
+        StatelessProcessScheduler processScheduler = null;
+        FlowFileRepository flowFileRepo = null;
+        FlowFileEventRepository flowFileEventRepo = null;
+
+        try {
+            final BulletinRepository bulletinRepository = new VolatileBulletinRepository();
+            final File workingDir = engineConfiguration.getWorkingDirectory();
+            if (!workingDir.exists() && !workingDir.mkdirs()) {
+                throw new IOException("Working Directory " + workingDir + " does not exist and could not be created");
+            }
+
+            final InMemoryFlowRegistry flowRegistry = new InMemoryFlowRegistry();
+            flowRegistry.addFlowSnapshot(flowSnapshot);
+            final FlowRegistryClient flowRegistryClient = new StandardFlowRegistryClient();
+            flowRegistryClient.addFlowRegistry(flowRegistry);
+
+            final File extensionsWorkingDir = new File(workingDir, "extensions");
+            final ClassLoader systemClassLoader = createSystemClassLoader(engineConfiguration.getNarDirectory());
+            final ExtensionDiscoveringManager extensionManager = ExtensionDiscovery.discover(extensionsWorkingDir, systemClassLoader);
+
+            flowFileEventRepo = new RingBufferEventRepository(5);
+
+            final StateProvider stateProvider = new HashMapStateProvider();
+            final StateManagerProvider stateManagerProvider = new StandardStateManagerProvider(stateProvider, stateProvider);
+
+            final ParameterContextManager parameterContextManager = new StandardParameterContextManager();
+            processScheduler = new StatelessProcessScheduler(extensionManager);
+            provenanceRepo = new VolatileProvenanceRepository(1_000, "", "");
+            provenanceRepo.initialize(EventReporter.NO_OP, new StatelessAuthorizer(), new StatelessProvenanceAuthorizableFactory(), IdentifierLookup.EMPTY);
+
+            final SSLContext sslContext;
+            try {
+                sslContext = SslConfigurationUtil.createSslContext(engineConfiguration.getSslContext());
+            } catch (StatelessConfigurationException e) {
+                throw new StatelessConfigurationException("Could not create SSLContext", e);
+            }
+
+            // Build Extension Repository
+            final NarClassLoaders narClassLoaders = NarClassLoadersHolder.getInstance();
+            final List<ExtensionClient> extensionClients = new ArrayList<>();
+            for (final ExtensionClientDefinition extensionClientDefinition : engineConfiguration.getExtensionClients()) {
+                final ExtensionClient extensionClient = createExtensionClient(extensionClientDefinition, engineConfiguration.getSslContext());
+                extensionClients.add(extensionClient);
+            }
+
+            final ExtensionRepository extensionRepository = new FileSystemExtensionRepository(extensionManager, engineConfiguration.getNarDirectory(), engineConfiguration.getWorkingDirectory(),
+                narClassLoaders, extensionClients);
+
+            final VariableRegistry variableRegistry = VariableRegistry.EMPTY_REGISTRY;
+            final StringEncryptor encryptor = StringEncryptor.createEncryptor("PBEWITHMD5AND256BITAES-CBC-OPENSSL", "BC", engineConfiguration.getSensitivePropsKey());
+
+            final File krb5File = engineConfiguration.getKrb5File();
+            final KerberosConfig kerberosConfig = new KerberosConfig(null, null, krb5File);
+            logger.info("Setting java.security.krb5.conf to {}", krb5File.getAbsolutePath());
+            System.setProperty("java.security.krb5.conf", krb5File.getAbsolutePath());
+
+            final StatelessEngine<VersionedFlowSnapshot> statelessEngine = new StandardStatelessEngine.Builder()
+                .bulletinRepository(bulletinRepository)
+                .encryptor(encryptor)
+                .extensionManager(extensionManager)
+                .flowRegistryClient(flowRegistryClient)
+                .stateManagerProvider(stateManagerProvider)
+                .variableRegistry(variableRegistry)
+                .processScheduler(processScheduler)
+                .kerberosConfiguration(kerberosConfig)
+                .flowFileEventRepository(flowFileEventRepo)
+                .provenanceRepository(provenanceRepo)
+                .extensionRepository(extensionRepository)
+                .build();
+
+            final StatelessFlowManager flowManager = new StatelessFlowManager(flowFileEventRepo, parameterContextManager, statelessEngine, () -> true, sslContext);
+            final ControllerServiceProvider controllerServiceProvider = new StandardControllerServiceProvider(processScheduler, bulletinRepository, flowManager, extensionManager);
+
+            final ProcessContextFactory rawProcessContextFactory = new StatelessProcessContextFactory(controllerServiceProvider, encryptor, stateManagerProvider);
+            final ProcessContextFactory processContextFactory = new CachingProcessContextFactory(rawProcessContextFactory);
+            contentRepo = new ByteArrayContentRepository();
+            flowFileRepo = new StatelessFlowFileRepository();
+            final CounterRepository counterRepo = new StandardCounterRepository();
+
+            final RepositoryContextFactory repositoryContextFactory = new StatelessRepositoryContextFactory(contentRepo, flowFileRepo, flowFileEventRepo, counterRepo, provenanceRepo);
+            final StatelessEngineInitializationContext statelessEngineInitializationContext = new StatelessEngineInitializationContext(controllerServiceProvider, flowManager, processContextFactory,
+                repositoryContextFactory);
+
+            processScheduler.initialize(processContextFactory);
+            statelessEngine.initialize(statelessEngineInitializationContext);
+
+            // Initialize components. This is generally needed because of the interdependencies between the components.
+            // There are some circular dependencies that are resolved by passing objects via initialization rather than by providing to the constructors.
+            final ResourceClaimManager resourceClaimManager = new StandardResourceClaimManager();
+            contentRepo.initialize(resourceClaimManager);
+            flowFileRepo.initialize(resourceClaimManager);
+            flowManager.initialize(controllerServiceProvider);
+
+            // Create flow
+            final ProcessGroup rootGroup = flowManager.createProcessGroup("root");
+            rootGroup.setName("root");
+            flowManager.setRootGroup(rootGroup);
+
+            final StatelessDataflow dataflow = statelessEngine.createFlow(dataflowDefinition, parameterOverrides);
+            final long millis = System.currentTimeMillis() - start;
+            logger.info("NiFi Stateless Engine and Dataflow created and initialized in {} millis", millis);
+
+            return dataflow;
+        } catch (final Exception e) {
+            try {
+                if (provenanceRepo != null) {
+                    provenanceRepo.close();
+                }
+            } catch (final IOException ioe) {
+                e.addSuppressed(ioe);
+            }
+
+            if (contentRepo != null) {
+                contentRepo.shutdown();
+            }
+
+            if (processScheduler != null) {
+                processScheduler.shutdown();
+            }
+
+            if (flowFileRepo != null) {
+                try {
+                    flowFileRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            if (flowFileEventRepo != null) {
+                try {
+                    flowFileEventRepo.close();
+                } catch (final IOException ioe) {
+                    e.addSuppressed(ioe);
+                }
+            }
+
+            throw e;
+        }
+    }
+
+    private ExtensionClient createExtensionClient(final ExtensionClientDefinition definition, final SslContextDefinition sslContextDefinition) {
+        final String type = definition.getExtensionClientType();
+        if (!"nexus".equalsIgnoreCase(type.trim())) {
+            throw new IllegalArgumentException("Invalid Extension Client type: <" + definition.getExtensionClientType() +">. Currently, the only supported type is <nexus>");
+        }
+
+        final SslContextDefinition sslContext = (definition.isUseSslContext() && sslContextDefinition != null) ? sslContextDefinition : null;
+        return new NexusExtensionClient(definition.getBaseUrl(), sslContext, definition.getCommsTimeout());
+    }
+
+    private ClassLoader createSystemClassLoader(final File narDirectory) throws StatelessConfigurationException {
+        final ClassLoader systemClassLoader = StatelessDataflowFactory.class.getClassLoader();
+        final int javaMajorVersion = getJavaMajorVersion();
+        if (javaMajorVersion >= 11) {
+            // If running on Java 11 or greater, add the JAXB/activation/annotation libs to the classpath.
+            // TODO: Once the minimum Java version requirement of NiFi is 11, this processing should be removed.
+            // JAXB/activation/annotation will be added as an actual dependency via pom.xml.
+            return createJava11OrLaterSystemClassLoader(javaMajorVersion, narDirectory, systemClassLoader);
+        }
+
+        return systemClassLoader;
+    }
+
+    private ClassLoader createJava11OrLaterSystemClassLoader(final int javaMajorVersion, final File narDirectory, final ClassLoader parentClassLoader) throws StatelessConfigurationException {
+        final List<URL> java11JarFileUrls = new ArrayList<>();
+
+        final File java11Dir = new File(narDirectory, "java11");
+        if (!java11Dir.exists()) {
+            throw new StatelessConfigurationException("Could not create System-level ClassLoader because Java version is " + javaMajorVersion + " but could not find the requisite Java 11 libraries " +
+                "at " + java11Dir.getAbsolutePath());
+        }
+
+        final File[] java11JarFiles = java11Dir.listFiles(filename -> filename.getName().toLowerCase().endsWith(".jar"));
+        if (java11JarFiles == null || java11JarFiles.length == 0) {
+            throw new StatelessConfigurationException("Could not create System-level ClassLoader because Java version is " + javaMajorVersion + " but could not find the requisite Java 11 libraries " +
+                "at " + java11Dir.getAbsolutePath());
+        }
+
+        try {
+            for (final File file : java11JarFiles) {
+                java11JarFileUrls.add(file.toURI().toURL());
+            }
+        } catch (final Exception e) {
+            throw new StatelessConfigurationException("Could not create System-level ClassLoader", e);
+        }
+
+        final ClassLoader classLoader = new URLClassLoader(java11JarFileUrls.toArray(new URL[0]), parentClassLoader);
+        return classLoader;
+    }
+
+    private int getJavaMajorVersion() {

Review comment:
       There are several other places in the project that evaluate the Java version, so there should probably be another PR to refactor these methods into a shared utility class.




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