content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.util;
  
  import alluxio.conf.AlluxioConfiguration;
  import alluxio.conf.PropertyKey;
  import alluxio.master.block.BlockId;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.security.SecureRandom;
  import java.util.UUID;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Utility methods for working with an id in Alluxio.
   */
  @ThreadSafe
  public final class IdUtils {
    private static final Logger LOG = LoggerFactory.getLogger(IdUtils.class);
  
    public static final long INVALID_FILE_ID = -1;
    public static final long INVALID_WORKER_ID = -1;
    public static final long INVALID_MOUNT_ID = -1;
    public static final long ROOT_MOUNT_ID = 1;
    /**
     * The journal ufs is stored as a special mount in the ufs manage.
     */
    public static final long UFS_JOURNAL_MOUNT_ID = Long.MAX_VALUE - 10000;
    private static SecureRandom sRandom = new SecureRandom();
  
    private IdUtils() {} // prevent instantiation
  
    /**
     * Creates an id for a file based on the given id of the container.
     *
     * @param containerId the id of the container
     * @return a file id based on the given container id
     */
    public static long createFileId(long containerId) {
      long id = BlockId.createBlockId(containerId, BlockId.getMaxSequenceNumber());
      if (id == INVALID_FILE_ID) {
        // Right now, there's not much we can do if the file id we're returning is -1, since the file
        // id is completely determined by the container id passed in. However, by the current
        // algorithm, -1 will be the last file id generated, so the chances somebody will get to that
        // are slim. For now we just log it.
        LOG.warn("Created file id -1, which is invalid");
      }
      return id;
    }
  
    /**
     * Creates a file ID from a block ID.
     *
     * @param blockId the block ID
     * @return the file ID
     */
    public static long fileIdFromBlockId(long blockId) {
      return createFileId(BlockId.getContainerId(blockId));
    }
  
    /**
     * @return the created RPC id
     */
    public static String createRpcId() {
      return UUID.randomUUID().toString();
    }
  
    /**
     * Generates a positive random number by zero-ing the sign bit.
     *
     * @return a random long which is guaranteed to be non negative (zero is allowed)
     */
    public static synchronized long getRandomNonNegativeLong() {
      return sRandom.nextLong() & Long.MAX_VALUE;
    }
  
    /**
     * @return a session ID
     */
    public static long createSessionId() {
      return getRandomNonNegativeLong();
    }
  
    /**
     * @return a random long which is guaranteed to be non negative (zero is allowed)
     */
    public static long createMountId() {
      return getRandomNonNegativeLong();
    }
  
    /**
     * @return app suffixed by a positive random long
     */
    public static String createFileSystemContextId() {
      return "app-" + getRandomNonNegativeLong();
    }
  
    /**
     *
     * @param conf an alluxio configuration with the USER_APP_ID property key
     * @return a string representing the USER_APP_ID
     */
    public static String createOrGetAppIdFromConfig(AlluxioConfiguration conf) {
      if (conf.isSet(PropertyKey.USER_APP_ID)) {
        return conf.getString(PropertyKey.USER_APP_ID);
      } else {
        return IdUtils.createFileSystemContextId();
      }
    }
  }
  