flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/EmbeddedCompletedCheckpointStore.java

/*
 * 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.checkpoint;

import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.api.common.JobStatus;
import org.apache.flink.util.Preconditions;

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/**
 * An embedded in-memory checkpoint store, which supports shutdown and suspend. You can use this to
 * test HA as long as the factory always returns the same store instance.
 */
public class EmbeddedCompletedCheckpointStore implements CompletedCheckpointStore {

    private final ArrayDeque<CompletedCheckpoint> checkpoints = new ArrayDeque<>(2);

    private final Collection<CompletedCheckpoint> suspended = new ArrayDeque<>(2);

    private final int maxRetainedCheckpoints;

    public EmbeddedCompletedCheckpointStore() {
        this(1);
    }

    EmbeddedCompletedCheckpointStore(int maxRetainedCheckpoints) {
        Preconditions.checkArgument(maxRetainedCheckpoints > 0);
        this.maxRetainedCheckpoints = maxRetainedCheckpoints;
    }

    @Override
    public void recover() {
        checkpoints.addAll(suspended);
        suspended.clear();
    }

    @Override
    public void addCheckpoint(
            CompletedCheckpoint checkpoint,
            CheckpointsCleaner checkpointsCleaner,
            Runnable postCleanup)
            throws Exception {
        checkpoints.addLast(checkpoint);

        CheckpointSubsumeHelper.subsume(
                checkpoints, maxRetainedCheckpoints, CompletedCheckpoint::discardOnSubsume);
    }

    @VisibleForTesting
    void removeOldestCheckpoint() throws Exception {
        CompletedCheckpoint checkpointToSubsume = checkpoints.removeFirst();
        checkpointToSubsume.discardOnSubsume();
    }

    @Override
    public void shutdown(
            JobStatus jobStatus, CheckpointsCleaner checkpointsCleaner, Runnable postCleanup)
            throws Exception {
        if (jobStatus.isGloballyTerminalState()) {
            checkpoints.clear();
            suspended.clear();
        } else {
            suspended.clear();
            suspended.addAll(checkpoints);
            checkpoints.clear();
        }
    }

    @Override
    public List<CompletedCheckpoint> getAllCheckpoints() {
        return new ArrayList<>(checkpoints);
    }

    @Override
    public int getNumberOfRetainedCheckpoints() {
        return checkpoints.size();
    }

    @Override
    public int getMaxNumberOfRetainedCheckpoints() {
        return maxRetainedCheckpoints;
    }

    @Override
    public boolean requiresExternalizedCheckpoints() {
        return false;
    }
}