[GitHub] [flink] TisonKun commented on a change in pull request #9788: [FLINK-14259] Introduce JobManagerRunner interface

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

TisonKun commented on a change in pull request #9788: [FLINK-14259] Introduce JobManagerRunner interface
URL: https://github.com/apache/flink/pull/9788#discussion_r329314925
 
 

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 File path: flink-runtime/src/main/java/org/apache/flink/runtime/jobmaster/JobManagerRunnerImpl.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.flink.runtime.jobmaster;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.runtime.client.JobExecutionException;
+import org.apache.flink.runtime.concurrent.FutureUtils;
+import org.apache.flink.runtime.execution.librarycache.LibraryCacheManager;
+import org.apache.flink.runtime.executiongraph.ArchivedExecutionGraph;
+import org.apache.flink.runtime.highavailability.HighAvailabilityServices;
+import org.apache.flink.runtime.highavailability.RunningJobsRegistry;
+import org.apache.flink.runtime.highavailability.RunningJobsRegistry.JobSchedulingStatus;
+import org.apache.flink.runtime.jobgraph.JobGraph;
+import org.apache.flink.runtime.jobmanager.OnCompletionActions;
+import org.apache.flink.runtime.jobmaster.factories.JobMasterServiceFactory;
+import org.apache.flink.runtime.leaderelection.LeaderContender;
+import org.apache.flink.runtime.leaderelection.LeaderElectionService;
+import org.apache.flink.runtime.messages.Acknowledge;
+import org.apache.flink.runtime.rpc.FatalErrorHandler;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.flink.util.FlinkException;
+import org.apache.flink.util.function.FunctionUtils;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nonnull;
+
+import java.io.IOException;
+import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.Executor;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * The runner for the job manager. It deals with job level leader election and make underlying job manager
+ * properly reacted.
+ */
+public class JobManagerRunnerImpl implements LeaderContender, OnCompletionActions, JobManagerRunner {
+
+	private static final Logger log = LoggerFactory.getLogger(JobManagerRunnerImpl.class);
+
+	// ------------------------------------------------------------------------
+
+	/** Lock to ensure that this runner can deal with leader election event and job completion notifies simultaneously. */
+	private final Object lock = new Object();
+
+	/** The job graph needs to run. */
+	private final JobGraph jobGraph;
+
+	/** Used to check whether a job needs to be run. */
+	private final RunningJobsRegistry runningJobsRegistry;
+
+	/** Leader election for this job. */
+	private final LeaderElectionService leaderElectionService;
+
+	private final LibraryCacheManager libraryCacheManager;
+
+	private final Executor executor;
+
+	private final JobMasterService jobMasterService;
+
+	private final FatalErrorHandler fatalErrorHandler;
+
+	private final CompletableFuture<ArchivedExecutionGraph> resultFuture;
+
+	private final CompletableFuture<Void> terminationFuture;
+
+	private CompletableFuture<Void> leadershipOperation;
+
+	/** flag marking the runner as shut down. */
+	private volatile boolean shutdown;
+
+	private volatile CompletableFuture<JobMasterGateway> leaderGatewayFuture;
+
+	// ------------------------------------------------------------------------
+
+	/**
+	 * Exceptions that occur while creating the JobManager or JobManagerRunner are directly
+	 * thrown and not reported to the given {@code FatalErrorHandler}.
+	 *
+	 * @throws Exception Thrown if the runner cannot be set up, because either one of the
+	 *                   required services could not be started, or the Job could not be initialized.
+	 */
+	public JobManagerRunnerImpl(
+			final JobGraph jobGraph,
+			final JobMasterServiceFactory jobMasterFactory,
+			final HighAvailabilityServices haServices,
+			final LibraryCacheManager libraryCacheManager,
+			final Executor executor,
+			final FatalErrorHandler fatalErrorHandler) throws Exception {
+
+		this.resultFuture = new CompletableFuture<>();
+		this.terminationFuture = new CompletableFuture<>();
+		this.leadershipOperation = CompletableFuture.completedFuture(null);
+
+		// make sure we cleanly shut down out JobManager services if initialization fails
+		try {
+			this.jobGraph = checkNotNull(jobGraph);
+			this.libraryCacheManager = checkNotNull(libraryCacheManager);
+			this.executor = checkNotNull(executor);
+			this.fatalErrorHandler = checkNotNull(fatalErrorHandler);
+
+			checkArgument(jobGraph.getNumberOfVertices() > 0, "The given job is empty");
+
+			// libraries and class loader first
+			try {
+				libraryCacheManager.registerJob(
+						jobGraph.getJobID(), jobGraph.getUserJarBlobKeys(), jobGraph.getClasspaths());
+			} catch (IOException e) {
+				throw new Exception("Cannot set up the user code libraries: " + e.getMessage(), e);
+			}
+
+			final ClassLoader userCodeLoader = libraryCacheManager.getClassLoader(jobGraph.getJobID());
+			if (userCodeLoader == null) {
+				throw new Exception("The user code class loader could not be initialized.");
+			}
+
+			// high availability services next
+			this.runningJobsRegistry = haServices.getRunningJobsRegistry();
+			this.leaderElectionService = haServices.getJobManagerLeaderElectionService(jobGraph.getJobID());
+
+			this.leaderGatewayFuture = new CompletableFuture<>();
+
+			// now start the JobManager
+			this.jobMasterService = jobMasterFactory.createJobMasterService(jobGraph, this, userCodeLoader);
+		}
+		catch (Throwable t) {
+			terminationFuture.completeExceptionally(t);
+			resultFuture.completeExceptionally(t);
+
+			throw new JobExecutionException(jobGraph.getJobID(), "Could not set up JobManager", t);
+		}
+	}
+
+	//----------------------------------------------------------------------------------------------
+	// Getter
+	//----------------------------------------------------------------------------------------------
+
+	@Override
+	public CompletableFuture<JobMasterGateway> getJobMasterGateway() {
+		return leaderGatewayFuture;
+	}
+
+	@Override
+	public CompletableFuture<ArchivedExecutionGraph> getResultFuture() {
+		return resultFuture;
+	}
+
+	@Override
+	public JobID getJobID() {
+		return jobGraph.getJobID();
+	}
+
+	//----------------------------------------------------------------------------------------------
+	// Lifecycle management
+	//----------------------------------------------------------------------------------------------
+
+	@Override
+	public void start() throws Exception {
+		try {
+			leaderElectionService.start(this);
+		} catch (Exception e) {
+			log.error("Could not start the JobManager because the leader election service did not start.", e);
+			throw new Exception("Could not start the leader election service.", e);
+		}
+	}
+
+	@Override
+	public CompletableFuture<Void> closeAsync() {
+		synchronized (lock) {
+			if (!shutdown) {
+				shutdown = true;
+
+				setNewLeaderGatewayFuture();
+				leaderGatewayFuture.completeExceptionally(new FlinkException("JobMaster has been shut down."));
+
+				final CompletableFuture<Void> jobManagerTerminationFuture = jobMasterService.closeAsync();
+
+				jobManagerTerminationFuture.whenComplete(
+					(Void ignored, Throwable throwable) -> {
+						try {
+							leaderElectionService.stop();
+						} catch (Throwable t) {
+							throwable = ExceptionUtils.firstOrSuppressed(t, ExceptionUtils.stripCompletionException(throwable));
+						}
+
+						libraryCacheManager.unregisterJob(jobGraph.getJobID());
+
+						if (throwable != null) {
+							terminationFuture.completeExceptionally(
+								new FlinkException("Could not properly shut down the JobManagerRunner", throwable));
+						} else {
+							terminationFuture.complete(null);
+						}
+					});
+
+				terminationFuture.whenComplete(
+					(Void ignored, Throwable throwable) -> {
+						resultFuture.completeExceptionally(new JobNotFinishedException(jobGraph.getJobID()));
+					});
+			}
+
+			return terminationFuture;
+		}
+	}
+
+	//----------------------------------------------------------------------------------------------
+	// Result and error handling methods
+	//----------------------------------------------------------------------------------------------
+
+	/**
+	 * Job completion notification triggered by JobManager.
+	 */
+	@Override
+	public void jobReachedGloballyTerminalState(ArchivedExecutionGraph executionGraph) {
+		unregisterJobFromHighAvailability();
+		// complete the result future with the terminal execution graph
+		resultFuture.complete(executionGraph);
+	}
+
+	/**
+	 * Job completion notification triggered by self.
+	 */
+	@Override
+	public void jobFinishedByOther() {
+		resultFuture.completeExceptionally(new JobNotFinishedException(jobGraph.getJobID()));
+	}
+
+	@Override
+	public void jobMasterFailed(Throwable cause) {
+		handleJobManagerRunnerError(cause);
+	}
+
+	private void handleJobManagerRunnerError(Throwable cause) {
+		if (ExceptionUtils.isJvmFatalError(cause)) {
+			fatalErrorHandler.onFatalError(cause);
+		} else {
+			resultFuture.completeExceptionally(cause);
+		}
+	}
+
+	/**
+	 * Marks this runner's job as not running. Other JobManager will not recover the job
+	 * after this call.
+	 *
+	 * <p>This method never throws an exception.
+	 */
+	private void unregisterJobFromHighAvailability() {
+		try {
+			runningJobsRegistry.setJobFinished(jobGraph.getJobID());
+		}
+		catch (Throwable t) {
+			log.error("Could not un-register from high-availability services job {} ({})." +
+					"Other JobManager's may attempt to recover it and re-execute it.",
+					jobGraph.getName(), jobGraph.getJobID(), t);
+		}
+	}
+
+	//----------------------------------------------------------------------------------------------
+	// Leadership methods
+	//----------------------------------------------------------------------------------------------
+
+	@Override
+	public void grantLeadership(final UUID leaderSessionID) {
+		synchronized (lock) {
+			if (shutdown) {
+				log.info("JobManagerRunner already shutdown.");
+				return;
+			}
+
+			leadershipOperation = leadershipOperation.thenCompose(
+				(ignored) -> {
+					synchronized (lock) {
+						return verifyJobSchedulingStatusAndStartJobManager(leaderSessionID);
+					}
+				});
+
+			handleException(leadershipOperation, "Could not start the job manager.");
+		}
+	}
+
+	private CompletableFuture<Void> verifyJobSchedulingStatusAndStartJobManager(UUID leaderSessionId) {
+		final CompletableFuture<JobSchedulingStatus> jobSchedulingStatusFuture = getJobSchedulingStatus();
+
+		return jobSchedulingStatusFuture.thenCompose(
+			jobSchedulingStatus -> {
+				if (jobSchedulingStatus == JobSchedulingStatus.DONE) {
+					return jobAlreadyDone();
+				} else {
+					return startJobMaster(leaderSessionId);
+				}
+			});
+	}
+
+	private CompletionStage<Void> startJobMaster(UUID leaderSessionId) {
+		log.info("JobManager runner for job {} ({}) was granted leadership with session id {} at {}.",
+			jobGraph.getName(), jobGraph.getJobID(), leaderSessionId, getAddress());
+
+		try {
+			runningJobsRegistry.setJobRunning(jobGraph.getJobID());
+		} catch (IOException e) {
+			return FutureUtils.completedExceptionally(
+				new FlinkException(
+					String.format("Failed to set the job %s to running in the running jobs registry.", jobGraph.getJobID()),
+					e));
+		}
+
+		final CompletableFuture<Acknowledge> startFuture;
+		try {
+			startFuture = jobMasterService.start(new JobMasterId(leaderSessionId));
+		} catch (Exception e) {
+			return FutureUtils.completedExceptionally(new FlinkException("Failed to start the JobMaster.", e));
+		}
+
+		final CompletableFuture<JobMasterGateway> currentLeaderGatewayFuture = leaderGatewayFuture;
+		return startFuture.thenAcceptAsync(
+			(Acknowledge ack) -> confirmLeaderSessionIdIfStillLeader(leaderSessionId, currentLeaderGatewayFuture),
+			executor);
+	}
+
+	@Nonnull
+	private CompletionStage<Void> jobAlreadyDone() {
+		log.info("Granted leader ship but job {} has been finished. ", jobGraph.getJobID());
+		jobFinishedByOther();
+		return CompletableFuture.completedFuture(null);
+	}
+
+	private CompletableFuture<JobSchedulingStatus> getJobSchedulingStatus() {
+		try {
+			JobSchedulingStatus jobSchedulingStatus = runningJobsRegistry.getJobSchedulingStatus(jobGraph.getJobID());
+			return CompletableFuture.completedFuture(jobSchedulingStatus);
+		} catch (IOException e) {
+			return FutureUtils.completedExceptionally(
+				new FlinkException(
+					String.format("Could not retrieve the job scheduling status for job %s.", jobGraph.getJobID()),
+					e));
+		}
+	}
+
+	private void confirmLeaderSessionIdIfStillLeader(UUID leaderSessionId, CompletableFuture<JobMasterGateway> currentLeaderGatewayFuture) {
+		if (leaderElectionService.hasLeadership(leaderSessionId)) {
 
 Review comment:
   Actually we don't gain anything from `hasLeadership` theoretically. Due to asynchronous operations between LeaderContender and LeaderElection on HA backend said ZK, even we get `true` here we can still fail because lost leadership later. I highly suspect that we can remove `hasLeadership` method (checks) because it misleads that it provides some guarantees.
   
   But it might be out of a refactor pull request, so just for information and follow-up sparks.

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