[GitHub] [sling-org-apache-sling-distribution-journal] tmaret commented on a change in pull request #17: SLING-8932 - Redesign DistributionSubscriber to offload responsibilities

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

tmaret commented on a change in pull request #17: SLING-8932 - Redesign DistributionSubscriber to offload responsibilities
URL: https://github.com/apache/sling-org-apache-sling-distribution-journal/pull/17#discussion_r360589594
 
 

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 File path: src/main/java/org/apache/sling/distribution/journal/impl/subscriber/BookKeeper.java
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+/*
+ * 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.sling.distribution.journal.impl.subscriber;
+
+import static java.lang.String.format;
+import static java.lang.System.currentTimeMillis;
+import static java.util.Collections.singletonMap;
+import static org.apache.sling.api.resource.ResourceResolverFactory.SUBSERVICE;
+import static org.apache.sling.distribution.journal.messages.Messages.PackageStatusMessage.Status.IMPORTED;
+import static org.apache.sling.distribution.journal.messages.Messages.PackageStatusMessage.Status.REMOVED;
+import static org.apache.sling.distribution.journal.messages.Messages.PackageStatusMessage.Status.REMOVED_FAILED;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+
+import org.apache.commons.io.IOUtils;
+import org.apache.sling.api.resource.LoginException;
+import org.apache.sling.api.resource.PersistenceException;
+import org.apache.sling.api.resource.ResourceResolver;
+import org.apache.sling.api.resource.ResourceResolverFactory;
+import org.apache.sling.api.resource.ValueMap;
+import org.apache.sling.commons.metrics.Timer;
+import org.apache.sling.distribution.common.DistributionException;
+import org.apache.sling.distribution.journal.impl.event.DistributionEvent;
+import org.apache.sling.distribution.journal.impl.queue.impl.PackageRetries;
+import org.apache.sling.distribution.journal.impl.shared.DistributionMetricsService;
+import org.apache.sling.distribution.journal.impl.shared.DistributionMetricsService.GaugeService;
+import org.apache.sling.distribution.journal.messages.Messages.PackageMessage;
+import org.apache.sling.distribution.journal.messages.Messages.PackageStatusMessage;
+import org.apache.sling.distribution.journal.messages.Messages.PackageStatusMessage.Status;
+import org.osgi.service.event.Event;
+import org.osgi.service.event.EventAdmin;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.slf4j.MDC;
+
+/**
+ * Keeps track of offset and processed status
+ * 
+ * The offset store is identified by the agentName only.
+ *
+ * With non clustered publish instances deployment, each
+ * instance stores the offset in its own node store, thus
+ * avoiding mix ups. Moreover, when cloning an instance
+ * from a node store, the cloned instance will implicitly
+ * recover the offsets and start from the last processed
+ * offset.
+ *
+ * With clustered publish instances deployment, only one
+ * Subscriber agent must run on the cluster in order to
+ * avoid mix ups.
+ *
+ * The clustered and non clustered publish instances use
+ * cases can be supported by only running the Subscriber
+ * agent on the leader instance.
+ */
+public class BookKeeper implements Closeable {
+    private static final String SUBSERVICE_BOOKKEEPER = "bookkeeper";
+    private static final int RETRY_SEND_DELAY = 1000;
+
+    private final Logger log = LoggerFactory.getLogger(this.getClass());
+    private final ResourceResolverFactory resolverFactory;
+    private final DistributionMetricsService distributionMetricsService;
+    private final EventAdmin eventAdmin;
+    private final Consumer<PackageStatusMessage> sender;
+    private final boolean editable;
+    private final int maxRetries;
+    private final boolean errorQueueEnabled;
+
+    private final PackageRetries packageRetries = new PackageRetries();
+    private final LocalStore statusStore;
+    private final LocalStore processedOffsets;
+    private final String subAgentName;
+    private final String subSlingId;
+    private GaugeService<Integer> retriesGauge;
+
+    public BookKeeper(ResourceResolverFactory resolverFactory, 
+            DistributionMetricsService distributionMetricsService,
+            EventAdmin eventAdmin,
+            Consumer<PackageStatusMessage> sender,
+            String subAgentName,
+            String subSlingId,
+            boolean editable, 
+            int maxRetries) { 
+        this.eventAdmin = eventAdmin;
+        String nameRetries = DistributionMetricsService.SUB_COMPONENT + ".current_retries;sub_name=" + subAgentName;
+        this.retriesGauge = distributionMetricsService.createGauge(nameRetries, "Retries of current package", packageRetries::getSum);
+        this.resolverFactory = resolverFactory;
+        this.distributionMetricsService = distributionMetricsService;
+        this.sender = sender;
+        this.subAgentName = subAgentName;
+        this.subSlingId = subSlingId;
+        this.editable = editable;
+        this.maxRetries = maxRetries;
+        // Error queues are enabled when the number
+        // of retry attempts is limited ; disabled otherwise
+        this.errorQueueEnabled = (maxRetries >= 0);
+        this.statusStore = new LocalStore(resolverFactory, "statuses", subAgentName);
+        this.processedOffsets = new LocalStore(resolverFactory, "packages", subAgentName);
+    }
+    
+    public void addPackageMDC(PackageMessage pkgMsg) {
+        MDC.put("module", "distribution");
+        MDC.put("package-id", pkgMsg.getPkgId());
+        String paths = pkgMsg.getPathsList().stream().collect(Collectors.joining(","));
+        MDC.put("paths", paths);
+        MDC.put("pub-sling-id", pkgMsg.getPubSlingId());
+        String pubAgentName = pkgMsg.getPubAgentName();
+        MDC.put("pub-agent-name", pubAgentName);
+        MDC.put("distribution-message-type", pkgMsg.getReqType().name());
+        MDC.put("retries", Integer.toString(packageRetries.get(pubAgentName)));
+        MDC.put("sub-sling-id", subSlingId);
+        MDC.put("sub-agent-name", subAgentName);
+    }
+    
+    public void imported(ResourceResolver importerResolver, PackageMessage pkgMsg, long offset, long createdTime)
+            throws PersistenceException {
+        if (editable) {
+            store(importerResolver, new PackageStatus(IMPORTED, offset, pkgMsg.getPubAgentName()));
+        }
+        storeOffset(importerResolver, offset);
+        distributionMetricsService.getImportedPackageSize().update(pkgMsg.getPkgLength());
+        distributionMetricsService.getPackageDistributedDuration().update((currentTimeMillis() - createdTime), TimeUnit.MILLISECONDS);
+        packageRetries.clear(pkgMsg.getPubAgentName());
+
+        Event event = DistributionEvent.eventImporterImported(pkgMsg, subAgentName);
+        eventAdmin.postEvent(event);
+    }
+    
+    /**
+     * Should be called on a exception while importing a package.
+     * 
+     * When we use an error queue and the max retries is reached the package is removed.
+     * In all other cases a DistributionException is thrown that signals that we should retry the
+     * package.
+     * 
+     * @param pkgMsg
+     * @param offset
+     * @param e
+     * @throws DistributionException if the package should be retried
+     */
+    public void failure(PackageMessage pkgMsg, long offset, Exception e) throws DistributionException {
+        distributionMetricsService.getFailedPackageImports().mark();
+
+        String pubAgentName = pkgMsg.getPubAgentName();
+        int retries = packageRetries.get(pubAgentName);
+        if (errorQueueEnabled && retries >= maxRetries) {
+            log.warn(format("Failed to import distribution package %s at offset %s after %s retries, removing the package.", pkgMsg.getPkgId(), offset, retries));
+            removeFailedPackage(pkgMsg, offset);
+        } else {
+            packageRetries.increase(pubAgentName);
+            String msg = format("Error processing distribution package %s. Retry attempts %s/%s.", pkgMsg.getPkgId(), retries, errorQueueEnabled ? Integer.toString(maxRetries) : "infinite");
+            throw new DistributionException(msg, e);
+        }
+    }
+
+    public void removePackage(PackageMessage pkgMsg, long offset) throws Exception {
+        log.info(format("Removing distribution package %s of type %s at offset %s", pkgMsg.getPkgId(), pkgMsg.getReqType(), offset));
+        Timer.Context context = distributionMetricsService.getRemovedPackageDuration().time();
+        try (ResourceResolver resolver = getServiceResolver()) {
+            if (editable) {
+                store(resolver, new PackageStatus(REMOVED, offset, pkgMsg.getPubAgentName()));
+            }
+            storeOffset(resolver, offset);
+            resolver.commit();
+        }
+        context.stop();
+    }
+
+    public void sendStoredStatus() throws InterruptedException, IOException {
+        try (Timer.Context context = distributionMetricsService.getSendStoredStatusDuration().time()) {
+            PackageStatus status = new PackageStatus(statusStore.load());
+            boolean sent = status.sent;
+            for (int retry = 0; !sent; retry++) {
+                sent = trySendStoredStatus(status, retry);
+            }
+        }
+    }
+
+    private boolean trySendStoredStatus(PackageStatus status, int retry) throws InterruptedException {
+        try {
+            PackageStatusMessage pkgStatMsg = PackageStatusMessage.newBuilder().setSubSlingId(subSlingId)
+                    .setSubAgentName(subAgentName).setPubAgentName(status.pubAgentName).setOffset(status.offset)
+                    .setStatus(status.status).build();
+            sender.accept(pkgStatMsg);
+            markStatusSent();
+            log.info("Sent status message {}", status);
+            return true;
+        } catch (Exception e) {
+            log.warn("Cannot send status (retry {})", retry, e);
+            Thread.sleep(RETRY_SEND_DELAY);
+            return false;
+        }
+    }
+
+    public void markStatusSent() {
+        try (ResourceResolver resolver = getServiceResolver()) {
+            statusStore.store(resolver, "sent", true);
+            resolver.commit();
+        } catch (Exception e) {
+            log.warn("Failed to mark status as sent", e);
+        }
+    }
+    
+    public long loadOffset() {
+        return  processedOffsets.load("offset", -1L);
+    }
+
+    public int getRetries(String pubAgentName) {
+        return packageRetries.get(pubAgentName);
+    }
+
+    public PackageRetries getPackageRetries() {
+        return packageRetries;
+    }
+
+    @Override
+    public void close() throws IOException {
+        IOUtils.closeQuietly(retriesGauge);
+    }
+    
+    private void removeFailedPackage(PackageMessage pkgMsg, long offset) throws DistributionException {
+        log.info(format("Removing failed distribution package %s of type %s at offset %s", pkgMsg.getPkgId(), pkgMsg.getReqType(), offset));
+        Timer.Context context = distributionMetricsService.getRemovedFailedPackageDuration().time();
+        try (ResourceResolver resolver = getServiceResolver()) {
+            store(resolver, new PackageStatus(REMOVED_FAILED, offset, pkgMsg.getPubAgentName()));
+            storeOffset(resolver, offset);
+            resolver.commit();
+        } catch (Exception e) {
+            throw new DistributionException("Error removing failed package", e);
+        }
+        context.stop();
+    }
+
+    private void store(ResourceResolver resolver, PackageStatus packageStatus) throws PersistenceException {
 
 Review comment:
   I think we should keep `storeStatus` because it effectively stores the status. Suggest to s/store/storeStatus back.
   

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