tillrohrmann commented on a change in pull request #9832: [FLINK-11843] Bind lifespan of Dispatcher to leader session URL: https://github.com/apache/flink/pull/9832#discussion_r339045019
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/dispatcher/runner/DefaultDispatcherRunner.java ########## @@ -0,0 +1,197 @@ +/* + * 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.dispatcher.runner; + +import org.apache.flink.runtime.clusterframework.ApplicationStatus; +import org.apache.flink.runtime.concurrent.FutureUtils; +import org.apache.flink.runtime.leaderelection.LeaderContender; +import org.apache.flink.runtime.leaderelection.LeaderElectionService; +import org.apache.flink.runtime.rpc.FatalErrorHandler; +import org.apache.flink.util.FlinkException; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.Arrays; +import java.util.UUID; +import java.util.concurrent.CompletableFuture; + +/** + * Runner for the {@link org.apache.flink.runtime.dispatcher.Dispatcher} which is responsible for the + * leader election. + */ +public final class DefaultDispatcherRunner implements DispatcherRunner, LeaderContender { + + private static final Logger LOG = LoggerFactory.getLogger(DefaultDispatcherRunner.class); + + private final Object lock = new Object(); + + private final LeaderElectionService leaderElectionService; + + private final FatalErrorHandler fatalErrorHandler; + + private final DispatcherLeaderProcessFactory dispatcherLeaderProcessFactory; + + private final CompletableFuture<Void> terminationFuture; + + private final CompletableFuture<ApplicationStatus> shutDownFuture; + + private boolean running; + + private DispatcherLeaderProcess dispatcherLeaderProcess; + + private CompletableFuture<Void> previousDispatcherLeaderProcessTerminationFuture; + + private DefaultDispatcherRunner( + LeaderElectionService leaderElectionService, + FatalErrorHandler fatalErrorHandler, + DispatcherLeaderProcessFactory dispatcherLeaderProcessFactory) { + this.leaderElectionService = leaderElectionService; + this.fatalErrorHandler = fatalErrorHandler; + this.dispatcherLeaderProcessFactory = dispatcherLeaderProcessFactory; + this.terminationFuture = new CompletableFuture<>(); + this.shutDownFuture = new CompletableFuture<>(); + + this.running = true; + this.dispatcherLeaderProcess = StoppedDispatcherLeaderProcess.INSTANCE; + this.previousDispatcherLeaderProcessTerminationFuture = CompletableFuture.completedFuture(null); + } + + @Override + public CompletableFuture<ApplicationStatus> getShutDownFuture() { + return shutDownFuture; + } + + @Override + public CompletableFuture<Void> closeAsync() { + synchronized (lock) { + if (!running) { + return terminationFuture; + } else { + running = false; + } + } + + stopDispatcherLeaderProcess(); + + FutureUtils.forward( + previousDispatcherLeaderProcessTerminationFuture, + terminationFuture); + + return terminationFuture; + } + + // --------------------------------------------------------------- + // Leader election + // --------------------------------------------------------------- + + @Override + public void grantLeadership(UUID leaderSessionID) { + runActionIfRunning(() -> startNewDispatcherLeaderProcess(leaderSessionID)); + } + + private void startNewDispatcherLeaderProcess(UUID leaderSessionID) { + stopDispatcherLeaderProcess(); + + dispatcherLeaderProcess = createNewDispatcherLeaderProcess(leaderSessionID); + + final DispatcherLeaderProcess newDispatcherLeaderProcess = dispatcherLeaderProcess; + FutureUtils.assertNoException( + previousDispatcherLeaderProcessTerminationFuture.thenRun(newDispatcherLeaderProcess::start)); + } + + private void stopDispatcherLeaderProcess() { + final CompletableFuture<Void> terminationFuture = dispatcherLeaderProcess.closeAsync(); + previousDispatcherLeaderProcessTerminationFuture = FutureUtils.completeAll( + Arrays.asList( + previousDispatcherLeaderProcessTerminationFuture, + terminationFuture)); + } + + private DispatcherLeaderProcess createNewDispatcherLeaderProcess(UUID leaderSessionID) { + LOG.debug("Create new {} with leader session id {}.", DispatcherLeaderProcess.class.getSimpleName(), leaderSessionID); + + final DispatcherLeaderProcess newDispatcherLeaderProcess = dispatcherLeaderProcessFactory.create(leaderSessionID); + + forwardShutDownFuture(newDispatcherLeaderProcess); + forwardConfirmLeaderSessionFuture(leaderSessionID, newDispatcherLeaderProcess); + + return newDispatcherLeaderProcess; + } + + private void forwardShutDownFuture(DispatcherLeaderProcess newDispatcherLeaderProcess) { + newDispatcherLeaderProcess.getShutDownFuture().whenComplete( + (applicationStatus, throwable) -> { + synchronized (lock) { + // ignore if no longer running or if leader processes is no longer valid + if (running && this.dispatcherLeaderProcess == newDispatcherLeaderProcess) { + if (throwable != null) { + shutDownFuture.completeExceptionally(throwable); + } else { + shutDownFuture.complete(applicationStatus); + } + } + } + }); + } + + private void forwardConfirmLeaderSessionFuture(UUID leaderSessionID, DispatcherLeaderProcess newDispatcherLeaderProcess) { + FutureUtils.assertNoException( + newDispatcherLeaderProcess.getLeaderAddressFuture().thenAccept( + leaderAddress -> { + if (leaderElectionService.hasLeadership(leaderSessionID)) { + leaderElectionService.confirmLeadership(leaderSessionID, leaderAddress); + } + })); + } + + @Override + public void revokeLeadership() { + runActionIfRunning(this::stopDispatcherLeaderProcess); + } + + private void runActionIfRunning(Runnable runnable) { + synchronized (lock) { + if (running) { + runnable.run(); + } else { + LOG.debug("Ignoring action because {} has already been stopped.", getClass().getSimpleName()); + } + } + } + + @Override + public void handleError(Exception exception) { + fatalErrorHandler.onFatalError( + new FlinkException( + String.format("Exception during leader election of %s occurred.", getClass().getSimpleName()), Review comment: True. Will remove it. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
