branch-2.0.4-alpha/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestNodeCount.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.blockmanagement;

import static org.junit.Assert.assertTrue;

import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.TimeoutException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.DFSTestUtil;
import org.apache.hadoop.hdfs.HdfsConfiguration;
import org.apache.hadoop.hdfs.MiniDFSCluster;
import org.apache.hadoop.hdfs.MiniDFSCluster.DataNodeProperties;
import org.apache.hadoop.hdfs.protocol.Block;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
import org.apache.hadoop.util.Time;
import org.junit.Test;

/**
 * Test if live nodes count per node is correct 
 * so NN makes right decision for under/over-replicated blocks
 * 
 * Two of the "while" loops below use "busy wait"
 * because they are detecting transient states.
 */
public class TestNodeCount {
  final short REPLICATION_FACTOR = (short)2;
  final long TIMEOUT = 20000L;
  long timeout = 0;
  long failtime = 0;
  Block lastBlock = null;
  NumberReplicas lastNum = null;

  @Test
  public void testNodeCount() throws Exception {
    // start a mini dfs cluster of 2 nodes
    final Configuration conf = new HdfsConfiguration();
    final MiniDFSCluster cluster = 
      new MiniDFSCluster.Builder(conf).numDataNodes(REPLICATION_FACTOR).build();
    try {
      final FSNamesystem namesystem = cluster.getNamesystem();
      final BlockManager bm = namesystem.getBlockManager();
      final HeartbeatManager hm = bm.getDatanodeManager().getHeartbeatManager();
      final FileSystem fs = cluster.getFileSystem();
      
      // populate the cluster with a one block file
      final Path FILE_PATH = new Path("/testfile");
      DFSTestUtil.createFile(fs, FILE_PATH, 1L, REPLICATION_FACTOR, 1L);
      DFSTestUtil.waitReplication(fs, FILE_PATH, REPLICATION_FACTOR);
      ExtendedBlock block = DFSTestUtil.getFirstBlock(fs, FILE_PATH);

      // keep a copy of all datanode descriptor
      final DatanodeDescriptor[] datanodes = hm.getDatanodes();
      
      // start two new nodes
      cluster.startDataNodes(conf, 2, true, null, null);
      cluster.waitActive();
      
      // bring down first datanode
      DatanodeDescriptor datanode = datanodes[0];
      DataNodeProperties dnprop = cluster.stopDataNode(datanode.getXferAddr());
      
      // make sure that NN detects that the datanode is down
      BlockManagerTestUtil.noticeDeadDatanode(
          cluster.getNameNode(), datanode.getXferAddr());
      
      // the block will be replicated
      DFSTestUtil.waitReplication(fs, FILE_PATH, REPLICATION_FACTOR);

      // restart the first datanode
      cluster.restartDataNode(dnprop);
      cluster.waitActive();
      
      // check if excessive replica is detected (transient)
      initializeTimeout(TIMEOUT);
      while (countNodes(block.getLocalBlock(), namesystem).excessReplicas() == 0) {
        checkTimeout("excess replicas not detected");
      }
      
      // find out a non-excess node
      final Iterator<DatanodeDescriptor> iter = bm.blocksMap
          .nodeIterator(block.getLocalBlock());
      DatanodeDescriptor nonExcessDN = null;
      while (iter.hasNext()) {
        DatanodeDescriptor dn = iter.next();
        Collection<Block> blocks = bm.excessReplicateMap.get(dn.getStorageID());
        if (blocks == null || !blocks.contains(block) ) {
          nonExcessDN = dn;
          break;
        }
      }
      assertTrue(nonExcessDN!=null);
      
      // bring down non excessive datanode
      dnprop = cluster.stopDataNode(nonExcessDN.getXferAddr());
      // make sure that NN detects that the datanode is down
      BlockManagerTestUtil.noticeDeadDatanode(
          cluster.getNameNode(), nonExcessDN.getXferAddr());

      // The block should be replicated
      initializeTimeout(TIMEOUT);
      while (countNodes(block.getLocalBlock(), namesystem).liveReplicas() != REPLICATION_FACTOR) {
        checkTimeout("live replica count not correct", 1000);
      }

      // restart the first datanode
      cluster.restartDataNode(dnprop);
      cluster.waitActive();

      // check if excessive replica is detected (transient)
      initializeTimeout(TIMEOUT);
      while (countNodes(block.getLocalBlock(), namesystem).excessReplicas() != 2) {
        checkTimeout("excess replica count not equal to 2");
      }

    } finally {
      cluster.shutdown();
    }
  }
  
  void initializeTimeout(long timeout) {
    this.timeout = timeout;
    this.failtime = Time.now()
        + ((timeout <= 0) ? Long.MAX_VALUE : timeout);
  }
  
  /* busy wait on transient conditions */
  void checkTimeout(String testLabel) throws TimeoutException {
    checkTimeout(testLabel, 0);
  }
  
  /* check for timeout, then wait for cycleTime msec */
  void checkTimeout(String testLabel, long cycleTime) throws TimeoutException {
    if (Time.now() > failtime) {
      throw new TimeoutException("Timeout: "
          + testLabel + " for block " + lastBlock + " after " + timeout 
          + " msec.  Last counts: live = " + lastNum.liveReplicas()
          + ", excess = " + lastNum.excessReplicas()
          + ", corrupt = " + lastNum.corruptReplicas());   
    }
    if (cycleTime > 0) {
      try {
        Thread.sleep(cycleTime);
      } catch (InterruptedException ie) {
        //ignore
      }
    }
  }

  /* threadsafe read of the replication counts for this block */
  NumberReplicas countNodes(Block block, FSNamesystem namesystem) {
    namesystem.readLock();
    try {
      lastBlock = block;
      lastNum = namesystem.getBlockManager().countNodes(block);
      return lastNum;
    }
    finally {
      namesystem.readUnlock();
    }
  }
}