hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestParallelImageWrite.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.server.namenode;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.io.File;
import java.util.Collections;
import java.util.List;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.DFSConfigKeys;
import org.apache.hadoop.hdfs.DFSTestUtil;
import org.apache.hadoop.hdfs.HdfsConfiguration;
import org.apache.hadoop.hdfs.MiniDFSCluster;
import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeDirType;
import org.junit.Test;

/**
 * A JUnit test for checking if restarting DFS preserves integrity.
 * Specifically with FSImage being written in parallel
 */
public class TestParallelImageWrite {
  private static final int NUM_DATANODES = 4;
  /** check if DFS remains in proper condition after a restart */
  @Test
  public void testRestartDFS() throws Exception {
    final Configuration conf = new HdfsConfiguration();
    MiniDFSCluster cluster = null;
    FSNamesystem fsn = null;
    int numNamenodeDirs;
    DFSTestUtil files = new DFSTestUtil.Builder().setName("TestRestartDFS").
        setNumFiles(200).build();

    final String dir = "/srcdat";
    final Path rootpath = new Path("/");
    final Path dirpath = new Path(dir);

    long rootmtime;
    FileStatus rootstatus;
    FileStatus dirstatus;

    try {
      cluster = new MiniDFSCluster.Builder(conf).format(true)
          .numDataNodes(NUM_DATANODES).build();
      String[] nameNodeDirs = conf.getStrings(
          DFSConfigKeys.DFS_NAMENODE_NAME_DIR_KEY, new String[] {});
      numNamenodeDirs = nameNodeDirs.length;
      assertTrue("failed to get number of Namenode StorageDirs", 
          numNamenodeDirs != 0);
      FileSystem fs = cluster.getFileSystem();
      files.createFiles(fs, dir);

      rootmtime = fs.getFileStatus(rootpath).getModificationTime();
      rootstatus = fs.getFileStatus(dirpath);
      dirstatus = fs.getFileStatus(dirpath);

      fs.setOwner(rootpath, rootstatus.getOwner() + "_XXX", null);
      fs.setOwner(dirpath, null, dirstatus.getGroup() + "_XXX");
    } finally {
      if (cluster != null) { cluster.shutdown(); }
    }
    try {
      // Force the NN to save its images on startup so long as
      // there are any uncheckpointed txns
      conf.setInt(DFSConfigKeys.DFS_NAMENODE_CHECKPOINT_TXNS_KEY, 1);

      // Here we restart the MiniDFScluster without formatting namenode
      cluster = new MiniDFSCluster.Builder(conf).format(false)
          .numDataNodes(NUM_DATANODES).build();
      fsn = cluster.getNamesystem();
      FileSystem fs = cluster.getFileSystem();
      assertTrue("Filesystem corrupted after restart.",
                 files.checkFiles(fs, dir));

      final FileStatus newrootstatus = fs.getFileStatus(rootpath);
      assertEquals(rootmtime, newrootstatus.getModificationTime());
      assertEquals(rootstatus.getOwner() + "_XXX", newrootstatus.getOwner());
      assertEquals(rootstatus.getGroup(), newrootstatus.getGroup());

      final FileStatus newdirstatus = fs.getFileStatus(dirpath);
      assertEquals(dirstatus.getOwner(), newdirstatus.getOwner());
      assertEquals(dirstatus.getGroup() + "_XXX", newdirstatus.getGroup());
      rootmtime = fs.getFileStatus(rootpath).getModificationTime();

      final String checkAfterRestart = checkImages(fsn, numNamenodeDirs);
      
      // Modify the system and then perform saveNamespace
      files.cleanup(fs, dir);
      files.createFiles(fs, dir);
      fsn.setSafeMode(SafeModeAction.SAFEMODE_ENTER);
      cluster.getNameNodeRpc().saveNamespace();
      final String checkAfterModify = checkImages(fsn, numNamenodeDirs);
      assertFalse("Modified namespace should change fsimage contents. " +
          "was: " + checkAfterRestart + " now: " + checkAfterModify,
          checkAfterRestart.equals(checkAfterModify));
      fsn.setSafeMode(SafeModeAction.SAFEMODE_LEAVE);
      files.cleanup(fs, dir);
    } finally {
      if (cluster != null) { cluster.shutdown(); }
    }
  }
  
  /**
   * Confirm that FSImage files in all StorageDirectory are the same,
   * and non-empty, and there are the expected number of them.
   * @param fsn - the FSNamesystem being checked.
   * @param numImageDirs - the configured number of StorageDirectory of type IMAGE. 
   * @return - the md5 hash of the most recent FSImage files, which must all be the same.
   * @throws AssertionError if image files are empty or different,
   *     if less than two StorageDirectory are provided, or if the
   *     actual number of StorageDirectory is less than configured.
   */
  public static String checkImages(
      FSNamesystem fsn, int numImageDirs)
  throws Exception {    
    NNStorage stg = fsn.getFSImage().getStorage();
    //any failed StorageDirectory is removed from the storageDirs list
    assertEquals("Some StorageDirectories failed Upgrade",
        numImageDirs, stg.getNumStorageDirs(NameNodeDirType.IMAGE));
    assertTrue("Not enough fsimage copies in MiniDFSCluster " + 
        "to test parallel write", numImageDirs > 1);

    // List of "current/" directory from each SD
    List<File> dirs = FSImageTestUtil.getCurrentDirs(stg, NameNodeDirType.IMAGE);

    // across directories, all files with same names should be identical hashes   
    FSImageTestUtil.assertParallelFilesAreIdentical(
        dirs, Collections.<String>emptySet());
    FSImageTestUtil.assertSameNewestImage(dirs);
    
    // Return the hash of the newest image file
    StorageDirectory firstSd = stg.dirIterator(NameNodeDirType.IMAGE).next();
    File latestImage = FSImageTestUtil.findLatestImageFile(firstSd);
    String md5 = FSImageTestUtil.getImageFileMD5IgnoringTxId(latestImage);
    System.err.println("md5 of " + latestImage + ": " + md5);
    return md5;
  }
}