hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/HdfsConstants.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.hadoop.hdfs.protocol;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.HdfsConfiguration;

/************************************
 * Some handy constants
 * 
 ************************************/
@InterfaceAudience.Private
public class HdfsConstants {
  /* Hidden constructor */
  protected HdfsConstants() {
  }

  public static int MIN_BLOCKS_FOR_WRITE = 5;

  // Long that indicates "leave current quota unchanged"
  public static final long QUOTA_DONT_SET = Long.MAX_VALUE;
  public static final long QUOTA_RESET = -1L;

  //
  // Timeouts, constants
  //
  public static final long LEASE_SOFTLIMIT_PERIOD = 60 * 1000;
  public static final long LEASE_HARDLIMIT_PERIOD = 60 * LEASE_SOFTLIMIT_PERIOD;
  public static final long LEASE_RECOVER_PERIOD = 10 * 1000; // in ms

  // We need to limit the length and depth of a path in the filesystem.
  // HADOOP-438
  // Currently we set the maximum length to 8k characters and the maximum depth
  // to 1k.
  public static int MAX_PATH_LENGTH = 8000;
  public static int MAX_PATH_DEPTH = 1000;

  // TODO mb@media-style.com: should be conf injected?
  public static final int DEFAULT_DATA_SOCKET_SIZE = 128 * 1024;
  public static final int IO_FILE_BUFFER_SIZE = new HdfsConfiguration().getInt(
      DFSConfigKeys.IO_FILE_BUFFER_SIZE_KEY,
      DFSConfigKeys.IO_FILE_BUFFER_SIZE_DEFAULT);
  // Used for writing header etc.
  public static final int SMALL_BUFFER_SIZE = Math.min(IO_FILE_BUFFER_SIZE / 2,
      512);

  public static final int BYTES_IN_INTEGER = Integer.SIZE / Byte.SIZE;

  // SafeMode actions
  public static enum SafeModeAction {
    SAFEMODE_LEAVE, SAFEMODE_ENTER, SAFEMODE_GET;
  }

  // type of the datanode report
  public static enum DatanodeReportType {
    ALL, LIVE, DEAD
  }

  // An invalid transaction ID that will never be seen in a real namesystem.
  public static final long INVALID_TXID = -12345;

  /**
   * Distributed upgrade actions:
   * 
   * 1. Get upgrade status. 2. Get detailed upgrade status. 3. Proceed with the
   * upgrade if it is stuck, no matter what the status is.
   */
  public static enum UpgradeAction {
    GET_STATUS, DETAILED_STATUS, FORCE_PROCEED;
  }

  /**
   * URI Scheme for hdfs://namenode/ URIs.
   */
  public static final String HDFS_URI_SCHEME = "hdfs";

  /**
   * Please see {@link LayoutVersion} on adding new layout version.
   */
  public static final int LAYOUT_VERSION = LayoutVersion
      .getCurrentLayoutVersion();
}