001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hdfs.client;
019
020import java.io.IOException;
021import java.net.URI;
022
023import org.apache.commons.logging.Log;
024import org.apache.commons.logging.LogFactory;
025import org.apache.hadoop.classification.InterfaceAudience;
026import org.apache.hadoop.classification.InterfaceStability;
027import org.apache.hadoop.conf.Configuration;
028import org.apache.hadoop.fs.CommonConfigurationKeysPublic;
029import org.apache.hadoop.fs.FileSystem;
030import org.apache.hadoop.hdfs.DFSConfigKeys;
031import org.apache.hadoop.hdfs.DistributedFileSystem;
032import org.apache.hadoop.hdfs.protocol.HdfsConstants;
033import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
034import org.apache.hadoop.io.IOUtils;
035
036/**
037 * The public utility API for HDFS.
038 */
039@InterfaceAudience.Public
040@InterfaceStability.Evolving
041public class HdfsUtils {
042  private static final Log LOG = LogFactory.getLog(HdfsUtils.class);
043
044  /**
045   * Is the HDFS healthy?
046   * HDFS is considered as healthy if it is up and not in safemode.
047   *
048   * @param uri the HDFS URI.  Note that the URI path is ignored.
049   * @return true if HDFS is healthy; false, otherwise.
050   */
051  public static boolean isHealthy(URI uri) {
052    //check scheme
053    final String scheme = uri.getScheme();
054    if (!HdfsConstants.HDFS_URI_SCHEME.equalsIgnoreCase(scheme)) {
055      throw new IllegalArgumentException("The scheme is not "
056          + HdfsConstants.HDFS_URI_SCHEME + ", uri=" + uri);
057    }
058    
059    final Configuration conf = new Configuration();
060    //disable FileSystem cache
061    conf.setBoolean(String.format("fs.%s.impl.disable.cache", scheme), true);
062    //disable client retry for rpc connection and rpc calls
063    conf.setBoolean(DFSConfigKeys.DFS_CLIENT_RETRY_POLICY_ENABLED_KEY, false);
064    conf.setInt(
065        CommonConfigurationKeysPublic.IPC_CLIENT_CONNECT_MAX_RETRIES_KEY, 0);
066
067    DistributedFileSystem fs = null;
068    try {
069      fs = (DistributedFileSystem)FileSystem.get(uri, conf);
070      final boolean safemode = fs.setSafeMode(SafeModeAction.SAFEMODE_GET);
071      if (LOG.isDebugEnabled()) {
072        LOG.debug("Is namenode in safemode? " + safemode + "; uri=" + uri);
073      }
074
075      fs.close();
076      fs = null;
077      return !safemode;
078    } catch(IOException e) {
079      if (LOG.isDebugEnabled()) {
080        LOG.debug("Got an exception for uri=" + uri, e);
081      }
082      return false;
083    } finally {
084      IOUtils.cleanup(LOG, fs);
085    }
086  }
087}