xintongsong commented on a change in pull request #13644: URL: https://github.com/apache/flink/pull/13644#discussion_r512440752
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/DefaultLeaderElectionService.java ########## @@ -0,0 +1,253 @@ +/* + * 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.util.Preconditions; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.Nonnull; +import javax.annotation.Nullable; +import javax.annotation.concurrent.GuardedBy; + +import java.util.Objects; +import java.util.UUID; + +/** + * Default implementation for leader election service. Composed with different {@link LeaderElectionDriver}, we could + * perform a leader election for the contender, and then persist the leader information to various storage. + */ +public class DefaultLeaderElectionService implements LeaderElectionService, LeaderElectionEventHandler { + + private static final Logger LOG = LoggerFactory.getLogger(DefaultLeaderElectionService.class); + + private final Object lock = new Object(); + + private final LeaderElectionDriverFactory leaderElectionDriverFactory; + + /** The leader contender which applies for leadership. */ + @GuardedBy("lock") + private volatile LeaderContender leaderContender; + + @GuardedBy("lock") + private volatile UUID issuedLeaderSessionID; + + @GuardedBy("lock") + private volatile UUID confirmedLeaderSessionID; + + @GuardedBy("lock") + private volatile String confirmedLeaderAddress; + + @GuardedBy("lock") + private volatile boolean running; + + @GuardedBy("lock") + private LeaderElectionDriver leaderElectionDriver; + + public DefaultLeaderElectionService(LeaderElectionDriverFactory leaderElectionDriverFactory) { + this.leaderElectionDriverFactory = leaderElectionDriverFactory; Review comment: minor: null check ########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/LeaderInformation.java ########## @@ -0,0 +1,86 @@ +/* + * 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 javax.annotation.Nullable; + +import java.io.Serializable; +import java.util.Objects; +import java.util.UUID; + +/** + * Information about leader including the confirmed leader session id and leader address. + */ +public class LeaderInformation implements Serializable { + + private static final long serialVersionUID = 1L; + + private final UUID leaderSessionID; + + private final String leaderAddress; + + private static final LeaderInformation EMPTY = new LeaderInformation(null, null); + + public LeaderInformation(@Nullable UUID leaderSessionID, @Nullable String leaderAddress) { + this.leaderSessionID = leaderSessionID; + this.leaderAddress = leaderAddress; + } + + @Nullable + public UUID getLeaderSessionID() { + return leaderSessionID; + } + + @Nullable + public String getLeaderAddress() { + return leaderAddress; + } + + @Override + public boolean equals(Object obj) { + if (obj == this) { + return true; + } else if (obj != null && obj.getClass() == LeaderInformation.class) { + final LeaderInformation that = (LeaderInformation) obj; + return Objects.equals(this.leaderSessionID, that.leaderSessionID) && + Objects.equals(this.leaderAddress, that.leaderAddress); + } else { + return false; + } + } + + @Override + public int hashCode() { + int result = leaderSessionID.hashCode(); Review comment: This may throw NPE if `leaderSessionID` is `null`. ########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/LeaderInformation.java ########## @@ -0,0 +1,86 @@ +/* + * 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 javax.annotation.Nullable; + +import java.io.Serializable; +import java.util.Objects; +import java.util.UUID; + +/** + * Information about leader including the confirmed leader session id and leader address. + */ +public class LeaderInformation implements Serializable { + + private static final long serialVersionUID = 1L; + + private final UUID leaderSessionID; + + private final String leaderAddress; Review comment: These 2 fields should also be annotated with `@Nullable`. ########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/leaderretrieval/DefaultLeaderRetrievalService.java ########## @@ -0,0 +1,143 @@ +/* + * 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.leaderretrieval; + +import org.apache.flink.runtime.leaderelection.LeaderInformation; +import org.apache.flink.util.Preconditions; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.concurrent.GuardedBy; + +import java.util.Objects; +import java.util.UUID; + +/** + * The counterpart to the {@link org.apache.flink.runtime.leaderelection.DefaultLeaderElectionService}. + * Composed with different {@link LeaderRetrievalDriver}, we could retrieve the leader information from + * different storage. The leader address as well as the current leader session ID will be retrieved from + * {@link LeaderRetrievalDriver}. + */ +public class DefaultLeaderRetrievalService implements LeaderRetrievalService, LeaderRetrievalEventHandler { + private static final Logger LOG = LoggerFactory.getLogger(DefaultLeaderRetrievalService.class); + + private final Object lock = new Object(); + + private final LeaderRetrievalDriverFactory leaderRetrievalDriverFactory; + + @GuardedBy("lock") + private String lastLeaderAddress; + + @GuardedBy("lock") + private UUID lastLeaderSessionID; + + @GuardedBy("lock") + private volatile boolean running; + + /** Listener which will be notified about leader changes. */ + @GuardedBy("lock") + private volatile LeaderRetrievalListener leaderListener; + + @GuardedBy("lock") + private LeaderRetrievalDriver leaderRetrievalDriver; + + /** + * Creates a default leader retrieval service with specified {@link LeaderRetrievalDriverFactory}. + * + * @param leaderRetrievalDriverFactory {@link LeaderRetrievalDriverFactory} used for creating + * {@link LeaderRetrievalDriver}. + */ + public DefaultLeaderRetrievalService(LeaderRetrievalDriverFactory leaderRetrievalDriverFactory) { + this.leaderRetrievalDriverFactory = leaderRetrievalDriverFactory; Review comment: null check ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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