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Posted to issues@flink.apache.org by GitBox <gi...@apache.org> on 2021/10/18 10:26:16 UTC
[GitHub] [flink] rkhachatryan commented on a change in pull request #16606: [FLINK-21357][runtime/statebackend]Periodic materialization for generalized incremental checkpoints
rkhachatryan commented on a change in pull request #16606:
URL: https://github.com/apache/flink/pull/16606#discussion_r730782566
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File path: flink-state-backends/flink-statebackend-changelog/src/main/java/org/apache/flink/state/changelog/PeriodicMaterializationManager.java
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@@ -0,0 +1,269 @@
+/*
+ * 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.flink.state.changelog;
+
+import org.apache.flink.api.common.operators.MailboxExecutor;
+import org.apache.flink.core.fs.FileSystemSafetyNet;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.runtime.state.StateObject;
+import org.apache.flink.runtime.state.changelog.SequenceNumber;
+import org.apache.flink.runtime.taskmanager.AsyncExceptionHandler;
+import org.apache.flink.util.concurrent.ExecutorThreadFactory;
+import org.apache.flink.util.concurrent.FutureUtils;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.Closeable;
+import java.util.Optional;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/** Stateless Materialization Manager. */
+public class PeriodicMaterializationManager implements Closeable {
+ private static final Logger LOG = LoggerFactory.getLogger(PeriodicMaterializationManager.class);
+
+ /** task mailbox executor, execute from Task Thread. */
+ private final MailboxExecutor mailboxExecutor;
+
+ /** Async thread pool, to complete async phase of materialization. */
+ private final ExecutorService asyncOperationsThreadPool;
+
+ /** scheduled executor, periodically trigger materialization. */
+ private final ScheduledExecutorService periodicExecutor;
+
+ private final AsyncExceptionHandler asyncExceptionHandler;
+
+ private final String subtaskName;
+
+ private final long periodicMaterializeDelay;
+
+ /** Allowed number of consecutive materialization failures. */
+ private final int allowedNumberOfFailures;
+
+ /** Number of consecutive materialization failures. */
+ private final AtomicInteger numberOfConsecutiveFailures;
+
+ private final ChangelogKeyedStateBackend<?> keyedStateBackend;
+
+ private boolean started = false;
+
+ PeriodicMaterializationManager(
+ MailboxExecutor mailboxExecutor,
+ ExecutorService asyncOperationsThreadPool,
+ String subtaskName,
+ AsyncExceptionHandler asyncExceptionHandler,
+ ChangelogKeyedStateBackend<?> keyedStateBackend,
+ long periodicMaterializeDelay,
+ int allowedNumberOfFailures) {
+ this.mailboxExecutor = checkNotNull(mailboxExecutor);
+ this.asyncOperationsThreadPool = checkNotNull(asyncOperationsThreadPool);
+ this.subtaskName = checkNotNull(subtaskName);
+ this.asyncExceptionHandler = checkNotNull(asyncExceptionHandler);
+ this.keyedStateBackend = checkNotNull(keyedStateBackend);
+
+ this.periodicMaterializeDelay = periodicMaterializeDelay;
+ this.allowedNumberOfFailures = allowedNumberOfFailures;
+ this.numberOfConsecutiveFailures = new AtomicInteger(0);
+
+ this.periodicExecutor =
+ Executors.newSingleThreadScheduledExecutor(
+ new ExecutorThreadFactory(
+ "periodic-materialization-scheduler-" + subtaskName));
+ }
+
+ public void start() {
+ if (!started) {
+
+ started = true;
+
+ LOG.info(
+ "Task {} starts periodic materialization, scheduling the next one in {} seconds",
+ subtaskName,
+ periodicMaterializeDelay / 1000);
+
+ scheduleNextMaterialization();
+ }
+ }
+
+ private void triggerMaterialization() {
+ mailboxExecutor.execute(
+ () -> {
+ Optional<MaterializationRunnable> materializationRunnableOptional =
+ keyedStateBackend.initMaterialization();
+
+ if (materializationRunnableOptional.isPresent()) {
+ MaterializationRunnable runnable = materializationRunnableOptional.get();
+ asyncOperationsThreadPool.execute(
+ () ->
+ asyncMaterializationPhase(
+ runnable.getMaterializationRunnable(),
+ runnable.getMaterializedTo()));
+ } else {
+ scheduleNextMaterialization();
+
+ LOG.info(
+ "Task {} has no state updates since last materialization, "
+ + "skip this one and schedule the next one in {} seconds",
+ subtaskName,
+ periodicMaterializeDelay / 1000);
+ }
+ },
+ "materialization");
+ }
+
+ private void asyncMaterializationPhase(
+ RunnableFuture<SnapshotResult<KeyedStateHandle>> materializedRunnableFuture,
+ SequenceNumber upTo) {
+
+ SnapshotResult<KeyedStateHandle> materializedSnapshot =
+ uploadSnapshot(materializedRunnableFuture);
+
+ // if succeed, update state and finish up
+ if (materializedSnapshot != null) {
+
+ numberOfConsecutiveFailures.set(0);
+
+ final SnapshotResult<KeyedStateHandle> copyMaterializedSnapshot = materializedSnapshot;
+
+ mailboxExecutor.execute(
+ () ->
+ keyedStateBackend.updateChangelogSnapshotState(
+ copyMaterializedSnapshot,
+ upTo),
+ "Task {} update materializedSnapshot up to changelog sequence number: {}",
+ subtaskName,
+ upTo);
+ }
+
+ LOG.info(
+ "Task {} schedules the next materialization in {} seconds.",
+ subtaskName,
+ periodicMaterializeDelay / 1000);
+
+ scheduleNextMaterialization();
+ }
+
+ private SnapshotResult<KeyedStateHandle> uploadSnapshot(
+ RunnableFuture<SnapshotResult<KeyedStateHandle>> materializedRunnableFuture) {
+
+ FileSystemSafetyNet.initializeSafetyNetForThread();
+ try {
+ FutureUtils.runIfNotDoneAndGet(materializedRunnableFuture);
+
+ LOG.debug("Task {} finishes asynchronous part of materialization.", subtaskName);
+
+ return materializedRunnableFuture.get();
+
+ } catch (Exception e) {
+ int retryTime = numberOfConsecutiveFailures.incrementAndGet();
+
+ LOG.info(
+ "Task {} asynchronous part of materialization is not completed for the {} time.",
+ subtaskName,
+ retryTime,
+ e);
+
+ discardFailedUploads(materializedRunnableFuture);
+
+ if (retryTime >= allowedNumberOfFailures) {
+ // Fail the task externally, this causes task failover
+ asyncExceptionHandler.handleAsyncException(
+ "Task "
+ + subtaskName
+ + " fails to complete the asynchronous part of materialization",
+ e);
+ }
+ } finally {
+ FileSystemSafetyNet.closeSafetyNetAndGuardedResourcesForThread();
+ }
+
+ return null;
+ }
+
+ private void discardFailedUploads(
+ RunnableFuture<SnapshotResult<KeyedStateHandle>> materializedRunnableFuture) {
+
+ LOG.info("Task {} cleanup asynchronous runnable for materialization.", subtaskName);
+
+ if (materializedRunnableFuture != null) {
+ // materialization has started
+ if (!materializedRunnableFuture.cancel(true)) {
+ try {
+ StateObject stateObject = materializedRunnableFuture.get();
+ if (stateObject != null) {
+ stateObject.discardState();
+ }
+ } catch (Exception ex) {
+ LOG.debug(
+ "Task "
+ + subtaskName
+ + " cancelled execution of snapshot future runnable. "
+ + "Cancellation produced the following "
+ + "exception, which is expected and can be ignored.",
+ ex);
+ }
+ }
+ }
+ }
+
+ // Only be called in the task thread to simplify the threading model
+ private void scheduleNextMaterialization() {
+ periodicExecutor.schedule(
+ this::triggerMaterialization, periodicMaterializeDelay, TimeUnit.MILLISECONDS);
+ }
Review comment:
I think there is a race condition in the code you added to address this:
```
if (!shutdown) {
periodicExecutor.schedule(
```
Even with `shutdown` being `volatile`, it can be set by T1, then checked by T2, then executor closed by T1, then schedule attempt made by T2.
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