Github user mxm commented on a diff in the pull request:
https://github.com/apache/flink/pull/2435#discussion_r81310859
--- 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);
+ }
--- End diff --
What if the `stopped = true` is set here? It seems kind of arbitrary to
check at this point in time. Isn't it enough to put the `heartbeatMonitor` into
the ConcurrentHashMap and remove the above lines? If we really want to be sure
that no concurrency occurs while adding a new `HeartbeatMonitor`, why don't we
synchronize on a lock then?
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