content: /*
   * 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.carbondata.core.locks;
  
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  import java.nio.channels.FileLock;
  import java.nio.channels.OverlappingFileLockException;
  import java.nio.file.Paths;
  import java.nio.file.StandardOpenOption;
  
  import org.apache.carbondata.common.logging.LogServiceFactory;
  import org.apache.carbondata.core.datastore.impl.FileFactory;
  import org.apache.carbondata.core.util.CarbonUtil;
  import org.apache.carbondata.core.util.path.CarbonTablePath;
  
  import org.apache.log4j.Logger;
  
  /**
   * This class handles the file locking in the local file system.
   * This will be handled by using the file channel lock API.
   */
  public class LocalFileLock extends AbstractCarbonLock {
    /**
     * lockFileDir is the directory of the lock file.
     */
    private String lockFileDir;
  
    /**
     * channel is the FileChannel of the lock file.
     */
    private FileChannel channel;
  
    /**
     * fileLock NIO FileLock Object
     */
    private FileLock fileLock;
  
    /**
     * LOGGER for  logging the messages.
     */
    private static final Logger LOGGER =
        LogServiceFactory.getLogService(LocalFileLock.class.getName());
  
    /**
     * @param lockFileLocation
     * @param lockFile
     */
    public LocalFileLock(String lockFileLocation, String lockFile) {
      this.lockFileDir = CarbonTablePath.getLockFilesDirPath(lockFileLocation);
      this.lockFilePath = CarbonTablePath.getLockFilePath(lockFileLocation, lockFile);
      initRetry();
    }
  
    /**
     * Lock API for locking of the file channel of the lock file.
     *
     * @return
     */
    @Override
    public boolean lock() {
      try {
        if (!FileFactory.isFileExist(lockFileDir)) {
          FileFactory.mkdirs(lockFileDir);
        }
        if (!FileFactory.isFileExist(lockFilePath)) {
          FileFactory.createNewLockFile(lockFilePath);
        }
        if (channel != null) {
          CarbonUtil.closeStreams(channel);
          channel = null;
        }
        channel = FileChannel.open(Paths.get(lockFilePath), StandardOpenOption.WRITE,
            StandardOpenOption.APPEND);
        try {
          fileLock = channel.tryLock();
        } catch (OverlappingFileLockException e) {
          return false;
        }
        return null != fileLock;
      } catch (IOException e) {
        LOGGER.info(e.getMessage());
        return false;
      }
    }
  
    /**
     * Unlock API for unlocking of the acquired lock.
     *
     * @return
     */
    @Override
    public boolean unlock() {
      boolean status = false;
      try {
        if (null != fileLock) {
          fileLock.release();
          status = true;
        }
      } catch (IOException e) {
        status = false;
      } finally {
        CarbonUtil.closeStreams(channel);
      }
      return status;
    }
  }
  