zentol commented on a change in pull request #15019: URL: https://github.com/apache/flink/pull/15019#discussion_r591361119
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/executiongraph/DefaultVertexAttemptNumberStore.java ########## @@ -0,0 +1,56 @@ +/* + * 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.executiongraph; + +import org.apache.flink.runtime.jobgraph.JobVertexID; +import org.apache.flink.util.Preconditions; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.HashMap; +import java.util.List; +import java.util.Map; + +/** Maintains the attempt number per subtask. */ +public class DefaultVertexAttemptNumberStore implements MutableVertexAttemptNumberStore { + private final Map<JobVertexID, List<Integer>> vertexSubtaskToAttemptCounts = new HashMap<>(); + + private static final List<Integer> EMPTY = new ArrayList<>(0); + + @Override + public SubtaskAttemptNumberStore getAttemptCounts(JobVertexID vertexId) { + return new DefaultSubtaskAttemptNumberStore( + Collections.unmodifiableList( + new ArrayList<>( Review comment: It effectively creates a snapshot of the current state, whereas if you'd just return a `unmodifiableList` changes to the backing list are visible to the consumer. Currently it wouldn't hurt to not do it; it's just a safeguard in case the store is stored at some point in the EG. ---------------------------------------------------------------- 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: [email protected]
