[GitHub] flink pull request #2435: [FLINK-4478] [flip-6] Add HeartbeatManager

[mxm <gi...@git.apache.org>]

Github user mxm commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2435#discussion_r81313363
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/heartbeat/HeartbeatManagerImpl.java ---
    @@ -0,0 +1,328 @@
    +/*
    + * 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.heartbeat;
    +
    +import org.apache.flink.runtime.clusterframework.types.ResourceID;
    +import org.apache.flink.runtime.concurrent.AcceptFunction;
    +import org.apache.flink.runtime.concurrent.Future;
    +import org.apache.flink.util.Preconditions;
    +import org.slf4j.Logger;
    +
    +import javax.annotation.concurrent.ThreadSafe;
    +import java.util.Collection;
    +import java.util.concurrent.ConcurrentHashMap;
    +import java.util.concurrent.Executor;
    +import java.util.concurrent.ScheduledExecutorService;
    +import java.util.concurrent.ScheduledFuture;
    +import java.util.concurrent.TimeUnit;
    +import java.util.concurrent.atomic.AtomicReference;
    +
    +/**
    + * Heartbeat manager implementation. The heartbeat manager maintains a map of heartbeat monitors
    + * and resource IDs. Each monitor will be updated when a new heartbeat of the associated machine has
    + * been received. If the monitor detects that a heartbeat has timed out, it will notify the
    + * {@link HeartbeatListener} about it. A heartbeat times out iff no heartbeat signal has been
    + * received within a given timeout interval.
    + *
    + * @param <I> Type of the incoming heartbeat payload
    + * @param <O> Type of the outgoing heartbeat payload
    + */
    +@ThreadSafe
    +public class HeartbeatManagerImpl<I, O> implements HeartbeatManager<I, O>, HeartbeatTarget<I> {
    +
    +	/** Heartbeat timeout interval in milli seconds */
    +	private final long heartbeatTimeoutIntervalMs;
    +
    +	/** Resource ID which is used to mark one own's heartbeat signals */
    +	private final ResourceID ownResourceID;
    +
    +	/** Executor service used to run heartbeat timeout notifications */
    +	private final ScheduledExecutorService scheduledExecutorService;
    +
    +	protected final Logger log;
    +
    +	/** Map containing the heartbeat monitors associated with the respective resource ID */
    +	private final ConcurrentHashMap<ResourceID, HeartbeatManagerImpl.HeartbeatMonitor<O>> heartbeatTargets;
    +
    +	/** Execution context used to run future callbacks */
    +	private final Executor executor;
    +
    +	/** Heartbeat listener with which the heartbeat manager has been associated */
    +	private HeartbeatListener<I, O> heartbeatListener;
    +
    +	/** Running state of the heartbeat manager */
    +	protected boolean stopped;
    +
    +	public HeartbeatManagerImpl(
    +		long heartbeatTimeoutIntervalMs,
    +		ResourceID ownResourceID,
    +		Executor executor,
    +		ScheduledExecutorService scheduledExecutorService,
    +		Logger log) {
    +		Preconditions.checkArgument(heartbeatTimeoutIntervalMs > 0L, "The heartbeat timeout has to be larger than 0.");
    +
    +		this.heartbeatTimeoutIntervalMs = heartbeatTimeoutIntervalMs;
    +		this.ownResourceID = Preconditions.checkNotNull(ownResourceID);
    +		this.scheduledExecutorService = Preconditions.checkNotNull(scheduledExecutorService);
    +		this.log = Preconditions.checkNotNull(log);
    +		this.executor = Preconditions.checkNotNull(executor);
    +		this.heartbeatTargets = new ConcurrentHashMap<>(16);
    +
    +		stopped = true;
    +	}
    +
    +	//----------------------------------------------------------------------------------------------
    +	// Getters
    +	//----------------------------------------------------------------------------------------------
    +
    +	ResourceID getOwnResourceID() {
    +		return ownResourceID;
    +	}
    +
    +	Executor getExecutor() {
    +		return executor;
    +	}
    +
    +	HeartbeatListener<I, O> getHeartbeatListener() {
    +		return heartbeatListener;
    +	}
    +
    +	Collection<HeartbeatManagerImpl.HeartbeatMonitor<O>> getHeartbeatTargets() {
    +		return heartbeatTargets.values();
    +	}
    +
    +	//----------------------------------------------------------------------------------------------
    +	// HeartbeatManager methods
    +	//----------------------------------------------------------------------------------------------
    +
    +	@Override
    +	public void monitorTarget(ResourceID resourceID, HeartbeatTarget<O> heartbeatTarget) {
    +		if (!stopped) {
    +			if (heartbeatTargets.containsKey(resourceID)) {
    +				log.info("The target with resource ID {} is already been monitored.", resourceID);
    +			} else {
    +				HeartbeatManagerImpl.HeartbeatMonitor<O> heartbeatMonitor = new HeartbeatManagerImpl.HeartbeatMonitor<>(
    +					resourceID,
    +					heartbeatTarget,
    +					scheduledExecutorService,
    +					heartbeatListener,
    +					heartbeatTimeoutIntervalMs);
    +
    +				heartbeatTargets.put(
    +					resourceID,
    +					heartbeatMonitor);
    +
    +				// check if we have stopped in the meantime (concurrent stop operation)
    +				if (stopped) {
    +					heartbeatMonitor.cancel();
    +
    +					heartbeatTargets.remove(resourceID);
    +				}
    +			}
    +		}
    +	}
    +
    +	@Override
    +	public void unmonitorTarget(ResourceID resourceID) {
    +		if (!stopped) {
    +			HeartbeatManagerImpl.HeartbeatMonitor<O> heartbeatMonitor = heartbeatTargets.remove(resourceID);
    +
    +			if (heartbeatMonitor != null) {
    +				heartbeatMonitor.cancel();
    +			}
    +		}
    +	}
    +
    +	@Override
    +	public void start(HeartbeatListener<I, O> heartbeatListener) {
    +		Preconditions.checkState(stopped, "Cannot start an already started heartbeat manager.");
    +
    +		stopped = false;
    +
    +		this.heartbeatListener = Preconditions.checkNotNull(heartbeatListener);
    +	}
    +
    +	@Override
    +	public void stop() {
    +		stopped = true;
    +
    +		for (HeartbeatManagerImpl.HeartbeatMonitor<O> heartbeatMonitor : heartbeatTargets.values()) {
    +			heartbeatMonitor.cancel();
    +		}
    +
    +		heartbeatTargets.clear();
    +	}
    +
    +	//----------------------------------------------------------------------------------------------
    +	// HeartbeatTarget methods
    +	//----------------------------------------------------------------------------------------------
    +
    +	@Override
    +	public void sendHeartbeat(ResourceID resourceID, I payload) {
    +		if (!stopped) {
    +			log.debug("Received heartbeat from {}.", resourceID);
    +			reportHeartbeat(resourceID);
    +
    +			if (payload != null) {
    +				heartbeatListener.reportPayload(resourceID, payload);
    +			}
    +		}
    +	}
    +
    +	@Override
    +	public void requestHeartbeat(ResourceID resourceID, I payload) {
    +		if (!stopped) {
    +			log.debug("Received heartbeat request from {}.", resourceID);
    +
    +			final HeartbeatTarget<O> heartbeatTarget = reportHeartbeat(resourceID);
    +
    +			if (heartbeatTarget != null) {
    +				if (payload != null) {
    +					heartbeatListener.reportPayload(resourceID, payload);
    +				}
    +
    +				Future<O> futurePayload = heartbeatListener.retrievePayload();
    +
    +				if (futurePayload != null) {
    +					futurePayload.thenAcceptAsync(new AcceptFunction<O>() {
    +						@Override
    +						public void accept(O retrievedPayload) {
    +							heartbeatTarget.sendHeartbeat(getOwnResourceID(), retrievedPayload);
    +						}
    +					}, executor);
    +				} else {
    +					heartbeatTarget.sendHeartbeat(ownResourceID, null);
    +				}
    +			}
    +		}
    +	}
    +
    +	HeartbeatTarget<O> reportHeartbeat(ResourceID resourceID) {
    +		if (heartbeatTargets.containsKey(resourceID)) {
    +			HeartbeatManagerImpl.HeartbeatMonitor<O> heartbeatMonitor = heartbeatTargets.get(resourceID);
    +			heartbeatMonitor.reportHeartbeat();
    +
    +			return heartbeatMonitor.getHeartbeatTarget();
    +		} else {
    +			return null;
    +		}
    +	}
    +
    +	//----------------------------------------------------------------------------------------------
    +	// Utility classes
    +	//----------------------------------------------------------------------------------------------
    +
    +	/**
    +	 * Heartbeat monitor which manages the heartbeat state of the associated heartbeat target. The
    +	 * monitor notifies the {@link HeartbeatListener} whenever it has not seen a heartbeat signal
    +	 * in the specified heartbeat timeout interval. Each heartbeat signal resets this timer.
    +	 *
    +	 * @param <O> Type of the payload being sent to the associated heartbeat target
    +	 */
    +	static class HeartbeatMonitor<O> implements Runnable {
    +
    +		/** Resource ID of the monitored heartbeat target */
    +		private final ResourceID resourceID;
    +
    +		/** Associated heartbeat target */
    +		private final HeartbeatTarget<O> heartbeatTarget;
    +
    +		private final ScheduledExecutorService scheduledExecutorService;
    +
    +		/** Listener which is notified about heartbeat timeouts */
    +		private final HeartbeatListener<?, ?> heartbeatListener;
    +
    +		/** Maximum heartbeat timeout interval */
    +		private final long heartbeatTimeoutIntervalMs;
    +
    +		private volatile ScheduledFuture<?> futureTimeout;
    +
    +		private final AtomicReference<State> state = new AtomicReference<>(State.RUNNING);
    +
    +		HeartbeatMonitor(
    +			ResourceID resourceID,
    +			HeartbeatTarget<O> heartbeatTarget,
    +			ScheduledExecutorService scheduledExecutorService,
    +			HeartbeatListener<?, O> heartbeatListener,
    +			long heartbeatTimeoutIntervalMs) {
    +
    +			this.resourceID = Preconditions.checkNotNull(resourceID);
    +			this.heartbeatTarget = Preconditions.checkNotNull(heartbeatTarget);
    +			this.scheduledExecutorService = Preconditions.checkNotNull(scheduledExecutorService);
    +			this.heartbeatListener = Preconditions.checkNotNull(heartbeatListener);
    +
    +			Preconditions.checkArgument(heartbeatTimeoutIntervalMs >= 0L, "The heartbeat timeout interval has to be larger than 0.");
    +			this.heartbeatTimeoutIntervalMs = heartbeatTimeoutIntervalMs;
    +
    +			resetHeartbeatTimeout(heartbeatTimeoutIntervalMs);
    +		}
    +
    +		HeartbeatTarget<O> getHeartbeatTarget() {
    +			return heartbeatTarget;
    +		}
    +
    +		void reportHeartbeat() {
    +			resetHeartbeatTimeout(heartbeatTimeoutIntervalMs);
    +		}
    +
    +		void resetHeartbeatTimeout(long heartbeatTimeout) {
    +			if (state.get() == State.RUNNING) {
    +				cancelTimeout();
    +
    +				futureTimeout = scheduledExecutorService.schedule(this, heartbeatTimeout, TimeUnit.MILLISECONDS);
    +
    +				// Double check for concurrent accesses (e.g. a firing of the scheduled future)
    +				if (state.get() != State.RUNNING) {
    +					cancelTimeout();
    +				}
    --- End diff --
    
    This looks like an optimization. Is is really necessary? We can still change state after we have checked.


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