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/*
 * 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.blob;

import org.apache.flink.api.common.JobID;
import org.apache.flink.api.java.tuple.Tuple2;

import org.slf4j.Logger;

import java.io.File;
import java.nio.file.Files;
import java.util.Map;
import java.util.Set;
import java.util.TimerTask;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.Lock;

import static org.apache.flink.util.Preconditions.checkNotNull;

/** Cleanup task for transient BLOBs. */
class TransientBlobCleanupTask extends TimerTask {

    /** The log object used for debugging. */
    private final Logger log;

    /** Map to store the TTL of each element stored in the local storage. */
    private ConcurrentMap, Long> blobExpiryTimes;

    /** Lock to acquire before changing file contents. */
    private Lock writeLock;

    /** Local storage directory to work on. */
    private File storageDir;

    /**
     * Creates a new cleanup timer task working with the given parameters from {@link BlobServer}
     * and {@link TransientBlobCache}.
     *
     * @param blobExpiryTimes map to store the TTL of each element stored in the local storage
     * @param writeLock lock to acquire before changing file contents
     * @param storageDir local storage directory to work on
     * @param log logger instance for debugging
     */
    TransientBlobCleanupTask(
            ConcurrentMap, Long> blobExpiryTimes,
            Lock writeLock,
            File storageDir,
            Logger log) {
        this.blobExpiryTimes = checkNotNull(blobExpiryTimes);
        this.writeLock = checkNotNull(writeLock);
        this.storageDir = checkNotNull(storageDir);
        this.log = checkNotNull(log);
    }

    /** Cleans up transient BLOBs whose TTL is up, tolerating that files do not exist (anymore). */
    @Override
    public void run() {
        // let's cache the current time - we do not operate on a millisecond precision anyway
        final long currentTimeMillis = System.currentTimeMillis();
        // iterate through all entries and remove those where the current time is past their expiry
        Set, Long>> entries = blobExpiryTimes.entrySet();
        for (Map.Entry, Long> entry : entries) {
            if (currentTimeMillis >= entry.getValue()) {
                JobID jobId = entry.getKey().f0;
                BlobKey blobKey = entry.getKey().f1;

                final File localFile =
                        new File(
                                BlobUtils.getStorageLocationPath(
                                        storageDir.getAbsolutePath(), jobId, blobKey));

                // deleting the file or changing blobExpiryTimes' contents needs to be protected by
                // the lock
                writeLock.lock();

                try {
                    try {
                        Files.delete(localFile.toPath());
                    } catch (Exception e) {
                        log.error("Failed to delete local blob " + localFile.getAbsolutePath(), e);
                    }

                    if (!localFile.exists()) {
                        // this needs to happen inside the write lock in case of concurrent
                        // getFile() calls
                        entries.remove(entry);
                    }
                } finally {
                    writeLock.unlock();
                }
            }
        }
    }
}