/*
 * 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.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.Serializable;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Delegate class responsible for checkpoints cleaning and counting the number of checkpoints yet to
 * clean.
 */
public class CheckpointsCleaner implements Serializable {
    private static final Logger LOG = LoggerFactory.getLogger(CheckpointsCleaner.class);

    private final AtomicInteger numberOfCheckpointsToClean;

    public CheckpointsCleaner() {
        this.numberOfCheckpointsToClean = new AtomicInteger(0);
    }

    int getNumberOfCheckpointsToClean() {
        return numberOfCheckpointsToClean.get();
    }

    public void cleanCheckpoint(
            Checkpoint checkpoint,
            boolean shouldDiscard,
            Runnable postCleanAction,
            Executor executor) {
        numberOfCheckpointsToClean.incrementAndGet();
        executor.execute(
                () -> {
                    try {
                        if (shouldDiscard) {
                            try {
                                checkpoint.discard();
                            } catch (Exception e) {
                                LOG.warn(
                                        "Could not discard completed checkpoint {}.",
                                        checkpoint.getCheckpointID(),
                                        e);
                            }
                        }
                    } finally {
                        numberOfCheckpointsToClean.decrementAndGet();
                        postCleanAction.run();
                    }
                });
    }
}

@@ -904,16 +904,64 @@
 ctory;%0A%0A
+import javax.annotation.concurrent.ThreadSafe;%0A%0A
 import j
@@ -1189,16 +1189,28 @@
 an.%0A */%0A
+@ThreadSafe%0A
 public c

Annotate CheckpointsCleaner with @ThreadSafe