[GitHub] [flink] tillrohrmann commented on a change in pull request #17485: [FLINK-24038] Add support for single leader election per JobManager process

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tillrohrmann commented on a change in pull request #17485:
URL: https://github.com/apache/flink/pull/17485#discussion_r791046741



##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/DefaultMultipleComponentLeaderElectionService.java
##########
@@ -0,0 +1,285 @@
+/*
+ * 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.leaderelection;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.runtime.rpc.FatalErrorHandler;
+import org.apache.flink.util.ExceptionUtils;
+import org.apache.flink.util.ExecutorUtils;
+import org.apache.flink.util.FlinkException;
+import org.apache.flink.util.Preconditions;
+import org.apache.flink.util.concurrent.ExecutorThreadFactory;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+
+/**
+ * Default implementation of a {@link MultipleComponentLeaderElectionService} that allows to
+ * register multiple {@link LeaderElectionEventHandler}.
+ */
+public class DefaultMultipleComponentLeaderElectionService
+        implements MultipleComponentLeaderElectionService,
+                MultipleComponentLeaderElectionDriver.Listener {
+    private static final Logger LOG =
+            LoggerFactory.getLogger(DefaultMultipleComponentLeaderElectionService.class);
+
+    private final Object lock = new Object();
+
+    private final MultipleComponentLeaderElectionDriver multipleComponentLeaderElectionDriver;
+
+    private final FatalErrorHandler fatalErrorHandler;
+
+    @GuardedBy("lock")
+    private final ExecutorService leadershipOperationExecutor;
+
+    @GuardedBy("lock")
+    private final Map<String, LeaderElectionEventHandler> leaderElectionEventHandlers;
+
+    private boolean running = true;
+
+    @Nullable
+    @GuardedBy("lock")
+    private UUID currentLeaderSessionId = null;
+
+    @VisibleForTesting
+    DefaultMultipleComponentLeaderElectionService(
+            FatalErrorHandler fatalErrorHandler,
+            String leaderContenderDescription,
+            MultipleComponentLeaderElectionDriverFactory
+                    multipleComponentLeaderElectionDriverFactory,
+            ExecutorService leadershipOperationExecutor)
+            throws Exception {
+        this.fatalErrorHandler = fatalErrorHandler;
+
+        this.leadershipOperationExecutor = leadershipOperationExecutor;
+
+        leaderElectionEventHandlers = new HashMap<>();
+
+        multipleComponentLeaderElectionDriver =
+                multipleComponentLeaderElectionDriverFactory.create(
+                        leaderContenderDescription, this);
+    }
+
+    public DefaultMultipleComponentLeaderElectionService(
+            FatalErrorHandler fatalErrorHandler,
+            String leaderContenderDescription,
+            MultipleComponentLeaderElectionDriverFactory
+                    multipleComponentLeaderElectionDriverFactory)
+            throws Exception {
+        this(
+                fatalErrorHandler,
+                leaderContenderDescription,
+                multipleComponentLeaderElectionDriverFactory,
+                java.util.concurrent.Executors.newSingleThreadExecutor(
+                        new ExecutorThreadFactory(
+                                String.format(
+                                        "leadershipOperation-%s", leaderContenderDescription))));
+    }
+
+    @Override
+    public void close() throws Exception {
+        synchronized (lock) {
+            if (!running) {
+                return;
+            }
+            running = false;
+
+            LOG.info("Closing {}.", this);
+
+            ExecutorUtils.gracefulShutdown(10L, TimeUnit.SECONDS, leadershipOperationExecutor);
+
+            Exception exception = null;
+            try {
+                multipleComponentLeaderElectionDriver.close();
+            } catch (Exception e) {
+                exception = e;
+            }
+
+            ExceptionUtils.tryRethrowException(exception);
+        }
+    }
+
+    @Override
+    public LeaderElectionDriverFactory createDriverFactory(String leaderName) {
+        return new MultipleComponentLeaderElectionDriverAdapterFactory(leaderName, this);
+    }
+
+    @Override
+    public void publishLeaderInformation(String leaderName, LeaderInformation leaderInformation) {
+        try {
+            multipleComponentLeaderElectionDriver.publishLeaderInformation(
+                    leaderName, leaderInformation);
+        } catch (Exception e) {
+            fatalErrorHandler.onFatalError(
+                    new FlinkException(
+                            String.format(
+                                    "Could not write leader information %s for leader %s.",
+                                    leaderInformation, leaderName),
+                            e));
+        }
+    }
+
+    @Override
+    public void registerLeaderElectionEventHandler(
+            String componentId, LeaderElectionEventHandler leaderElectionEventHandler) {
+
+        synchronized (lock) {
+            Preconditions.checkState(
+                    !leaderElectionEventHandlers.containsKey(componentId),
+                    "Do not support duplicate LeaderElectionEventHandler registration under %s",
+                    componentId);
+            leaderElectionEventHandlers.put(componentId, leaderElectionEventHandler);
+
+            if (currentLeaderSessionId != null) {
+                leadershipOperationExecutor.execute(
+                        () -> leaderElectionEventHandler.onGrantLeadership(currentLeaderSessionId));
+            }
+        }
+    }
+
+    @Override
+    public void unregisterLeaderElectionEventHandler(String componentId) throws Exception {
+        final LeaderElectionEventHandler unregisteredLeaderElectionEventHandler;
+        synchronized (lock) {
+            unregisteredLeaderElectionEventHandler =
+                    leaderElectionEventHandlers.remove(componentId);
+
+            if (unregisteredLeaderElectionEventHandler != null) {

Review comment:
       True. Will add it.




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