hdfs/src/test/hdfs/org/apache/hadoop/hdfs/TestDFSClientRetries.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;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.hdfs.DFSClient.DFSInputStream;
import org.apache.hadoop.hdfs.protocol.*;
import org.apache.hadoop.hdfs.protocol.FSConstants.UpgradeAction;
import org.apache.hadoop.hdfs.server.common.*;
import org.apache.hadoop.hdfs.server.namenode.NotReplicatedYetException;
import org.apache.hadoop.hdfs.server.namenode.NameNode;
import org.apache.hadoop.io.*;
import org.apache.hadoop.ipc.RemoteException;
import org.apache.hadoop.security.AccessControlException;

import junit.framework.TestCase;

import static org.mockito.Mockito.*;
import org.mockito.stubbing.Answer;
import org.mockito.invocation.InvocationOnMock;

/**
 * These tests make sure that DFSClient retries fetching data from DFS
 * properly in case of errors.
 */
public class TestDFSClientRetries extends TestCase {
  public static final Log LOG =
    LogFactory.getLog(TestDFSClientRetries.class.getName());
  
  // writes 'len' bytes of data to out.
  private static void writeData(OutputStream out, int len) throws IOException {
    byte [] buf = new byte[4096*16];
    while(len > 0) {
      int toWrite = Math.min(len, buf.length);
      out.write(buf, 0, toWrite);
      len -= toWrite;
    }
  }
  
  /**
   * This makes sure that when DN closes clients socket after client had
   * successfully connected earlier, the data can still be fetched.
   */
  public void testWriteTimeoutAtDataNode() throws IOException,
                                                  InterruptedException { 
    Configuration conf = new HdfsConfiguration();
    
    final int writeTimeout = 100; //milliseconds.
    // set a very short write timeout for datanode, so that tests runs fast.
    conf.setInt("dfs.datanode.socket.write.timeout", writeTimeout); 
    // set a smaller block size
    final int blockSize = 10*1024*1024;
    conf.setInt(DFSConfigKeys.DFS_BLOCK_SIZE_KEY, blockSize);
    conf.setInt("dfs.client.max.block.acquire.failures", 1);
    // set a small buffer size
    final int bufferSize = 4096;
    conf.setInt("io.file.buffer.size", bufferSize);

    MiniDFSCluster cluster = new MiniDFSCluster(conf, 3, true, null);
    
    try {
      cluster.waitActive();
      FileSystem fs = cluster.getFileSystem();
    
      Path filePath = new Path("/testWriteTimeoutAtDataNode");
      OutputStream out = fs.create(filePath, true, bufferSize);
    
      // write a 2 block file.
      writeData(out, 2*blockSize);
      out.close();
      
      byte[] buf = new byte[1024*1024]; // enough to empty TCP buffers.
      
      InputStream in = fs.open(filePath, bufferSize);
      
      //first read a few bytes
      IOUtils.readFully(in, buf, 0, bufferSize/2);
      //now read few more chunks of data by sleeping in between :
      for(int i=0; i<10; i++) {
        Thread.sleep(2*writeTimeout); // force write timeout at the datanode.
        // read enough to empty out socket buffers.
        IOUtils.readFully(in, buf, 0, buf.length); 
      }
      // successfully read with write timeout on datanodes.
      in.close();
    } finally {
      cluster.shutdown();
    }
  }
  
  // more tests related to different failure cases can be added here.
  
  class TestNameNode implements ClientProtocol
  {
    int num_calls = 0;
    
    // The total number of calls that can be made to addBlock
    // before an exception is thrown
    int num_calls_allowed; 
    public final String ADD_BLOCK_EXCEPTION = "Testing exception thrown from"
                                             + "TestDFSClientRetries::"
                                             + "TestNameNode::addBlock";
    public final String RETRY_CONFIG
          = "dfs.client.block.write.locateFollowingBlock.retries";
          
    public TestNameNode(Configuration conf) throws IOException
    {
      // +1 because the configuration value is the number of retries and
      // the first call is not a retry (e.g., 2 retries == 3 total
      // calls allowed)
      this.num_calls_allowed = conf.getInt(RETRY_CONFIG, 5) + 1;
    }

    public long getProtocolVersion(String protocol, 
                                     long clientVersion)
    throws IOException
    {
      return versionID;
    }

    public LocatedBlock addBlock(String src, String clientName,
                                 Block previous) throws IOException {

      return addBlock(src, clientName, previous, null);
    }

    public LocatedBlock addBlock(String src,
                                 String clientName,
                                 Block previous,
                                 DatanodeInfo[] excludedNode
                                 ) throws IOException
    {
      num_calls++;
      if (num_calls > num_calls_allowed) { 
        throw new IOException("addBlock called more times than "
                              + RETRY_CONFIG
                              + " allows.");
      } else {
          throw new RemoteException(NotReplicatedYetException.class.getName(),
                                    ADD_BLOCK_EXCEPTION);
      }
    }
    
    
    // The following methods are stub methods that are not needed by this mock class
    
    public LocatedBlocks  getBlockLocations(String src, long offset, long length) throws IOException { return null; }
    
    public FsServerDefaults getServerDefaults() throws IOException { return null; }
    
    public void create(String src, FsPermission masked, String clientName, EnumSetWritable<CreateFlag> flag, boolean createParent, short replication, long blockSize) throws IOException {}
    
    public LocatedBlock append(String src, String clientName) throws IOException { return null; }

    public boolean setReplication(String src, short replication) throws IOException { return false; }

    public void setPermission(String src, FsPermission permission) throws IOException {}

    public void setOwner(String src, String username, String groupname) throws IOException {}

    public void abandonBlock(Block b, String src, String holder) throws IOException {}

    public boolean complete(String src, String clientName, Block last) throws IOException { return false; }

    public void reportBadBlocks(LocatedBlock[] blocks) throws IOException {}

    public boolean rename(String src, String dst) throws IOException { return false; }

    public boolean delete(String src) throws IOException { return false; }

    public boolean delete(String src, boolean recursive) throws IOException { return false; }

    public boolean mkdirs(String src, FsPermission masked, boolean createParent) throws IOException { return false; }

    public FileStatus[] getListing(String src) throws IOException { return null; }

    public void renewLease(String clientName) throws IOException {}

    public long[] getStats() throws IOException { return null; }

    public DatanodeInfo[] getDatanodeReport(FSConstants.DatanodeReportType type) throws IOException { return null; }

    public long getPreferredBlockSize(String filename) throws IOException { return 0; }

    public boolean setSafeMode(FSConstants.SafeModeAction action) throws IOException { return false; }

    public void saveNamespace() throws IOException {}

    public boolean restoreFailedStorage(String arg) throws AccessControlException { return false; }

    public void refreshNodes() throws IOException {}

    public void finalizeUpgrade() throws IOException {}

    public UpgradeStatusReport distributedUpgradeProgress(UpgradeAction action) throws IOException { return null; }

    public void metaSave(String filename) throws IOException {}

    public FileStatus getFileInfo(String src) throws IOException { return null; }

    public ContentSummary getContentSummary(String path) throws IOException { return null; }

    public void setQuota(String path, long namespaceQuota, long diskspaceQuota) throws IOException {}

    public void fsync(String src, String client) throws IOException {}

    public void setTimes(String src, long mtime, long atime) throws IOException {}

    @Override public LocatedBlock updateBlockForPipeline(Block block, 
        String clientName) throws IOException { return null; }

    @Override public void updatePipeline(String clientName, Block oldblock,
        Block newBlock, DatanodeID[] newNodes)
        throws IOException {}
  }
  
  public void testNotYetReplicatedErrors() throws IOException
  {   
    Configuration conf = new HdfsConfiguration();
    
    // allow 1 retry (2 total calls)
    conf.setInt("dfs.client.block.write.locateFollowingBlock.retries", 1);
        
    TestNameNode tnn = new TestNameNode(conf);
    final DFSClient client = new DFSClient(null, tnn, conf, null);
    OutputStream os = client.create("testfile", true);
    os.write(20); // write one random byte
    
    try {
      os.close();
    } catch (Exception e) {
      assertTrue("Retries are not being stopped correctly",
           e.getMessage().equals(tnn.ADD_BLOCK_EXCEPTION));
    }
  }

  /**
   * This tests that DFSInputStream failures are counted for a given read
   * operation, and not over the lifetime of the stream. It is a regression
   * test for HDFS-127.
   */
  public void testFailuresArePerOperation() throws Exception
  {
    long fileSize = 4096;
    Path file = new Path("/testFile");

    Configuration conf = new Configuration();
    MiniDFSCluster cluster = new MiniDFSCluster(conf, 1, true, null);

    int maxBlockAcquires = DFSClient.getMaxBlockAcquireFailures(conf);
    assertTrue(maxBlockAcquires > 0);

    try {
      cluster.waitActive();
      FileSystem fs = cluster.getFileSystem();
      NameNode preSpyNN = cluster.getNameNode();
      NameNode spyNN = spy(preSpyNN);
      DFSClient client = new DFSClient(null, spyNN, conf, null);

      DFSTestUtil.createFile(fs, file, fileSize, (short)1, 12345L /*seed*/);

      // If the client will retry maxBlockAcquires times, then if we fail
      // any more than that number of times, the operation should entirely
      // fail.
      doAnswer(new FailNTimesAnswer(preSpyNN, maxBlockAcquires + 1))
        .when(spyNN).getBlockLocations(anyString(), anyLong(), anyLong());
      try {
        IOUtils.copyBytes(client.open(file.toString()), new IOUtils.NullOutputStream(), conf,
                          true);
        fail("Didn't get exception");
      } catch (IOException ioe) {
        DFSClient.LOG.info("Got expected exception", ioe);
      }

      // If we fail exactly that many times, then it should succeed.
      doAnswer(new FailNTimesAnswer(preSpyNN, maxBlockAcquires))
        .when(spyNN).getBlockLocations(anyString(), anyLong(), anyLong());
      IOUtils.copyBytes(client.open(file.toString()), new IOUtils.NullOutputStream(), conf,
                        true);

      DFSClient.LOG.info("Starting test case for failure reset");

      // Now the tricky case - if we fail a few times on one read, then succeed,
      // then fail some more on another read, it shouldn't fail.
      doAnswer(new FailNTimesAnswer(preSpyNN, maxBlockAcquires))
        .when(spyNN).getBlockLocations(anyString(), anyLong(), anyLong());
      DFSInputStream is = client.open(file.toString());
      byte buf[] = new byte[10];
      IOUtils.readFully(is, buf, 0, buf.length);

      DFSClient.LOG.info("First read successful after some failures.");

      // Further reads at this point will succeed since it has the good block locations.
      // So, force the block locations on this stream to be refreshed from bad info.
      // When reading again, it should start from a fresh failure count, since
      // we're starting a new operation on the user level.
      doAnswer(new FailNTimesAnswer(preSpyNN, maxBlockAcquires))
        .when(spyNN).getBlockLocations(anyString(), anyLong(), anyLong());
      is.openInfo();
      // Seek to beginning forces a reopen of the BlockReader - otherwise it'll
      // just keep reading on the existing stream and the fact that we've poisoned
      // the block info won't do anything.
      is.seek(0);
      IOUtils.readFully(is, buf, 0, buf.length);

    } finally {
      cluster.shutdown();
    }
  }

  /**
   * Mock Answer implementation of NN.getBlockLocations that will return
   * a poisoned block list a certain number of times before returning
   * a proper one.
   */
  private static class FailNTimesAnswer implements Answer<LocatedBlocks> {
    private int failuresLeft;
    private NameNode realNN;

    public FailNTimesAnswer(NameNode realNN, int timesToFail) {
      failuresLeft = timesToFail;
      this.realNN = realNN;
    }

    public LocatedBlocks answer(InvocationOnMock invocation) throws IOException {
      Object args[] = invocation.getArguments();
      LocatedBlocks realAnswer = realNN.getBlockLocations(
        (String)args[0],
        (Long)args[1],
        (Long)args[2]);

      if (failuresLeft-- > 0) {
        NameNode.LOG.info("FailNTimesAnswer injecting failure.");
        return makeBadBlockList(realAnswer);
      }
      NameNode.LOG.info("FailNTimesAnswer no longer failing.");
      return realAnswer;
    }

    private LocatedBlocks makeBadBlockList(LocatedBlocks goodBlockList) {
      LocatedBlock goodLocatedBlock = goodBlockList.get(0);
      LocatedBlock badLocatedBlock = new LocatedBlock(
        goodLocatedBlock.getBlock(),
        new DatanodeInfo[] {
          new DatanodeInfo(new DatanodeID("255.255.255.255:234"))
        },
        goodLocatedBlock.getStartOffset(),
        false);


      List<LocatedBlock> badBlocks = new ArrayList<LocatedBlock>();
      badBlocks.add(badLocatedBlock);
      return new LocatedBlocks(goodBlockList.getFileLength(), false,
                               badBlocks, null, true);
    }
  }

  public void testGetFileChecksum() throws Exception {
    final String f = "/testGetFileChecksum";
    final Path p = new Path(f);

    final Configuration conf = new Configuration();
    final MiniDFSCluster cluster = new MiniDFSCluster(conf, 3, true, null);
    try {
      cluster.waitActive();

      //create a file
      final FileSystem fs = cluster.getFileSystem();
      DFSTestUtil.createFile(fs, p, 1L << 20, (short)3, 20100402L);

      //get checksum
      final FileChecksum cs1 = fs.getFileChecksum(p);
      assertTrue(cs1 != null);

      //stop the first datanode
      final List<LocatedBlock> locatedblocks = DFSClient.callGetBlockLocations(
          cluster.getNameNode(), f, 0, Long.MAX_VALUE).getLocatedBlocks();
      final DatanodeInfo first = locatedblocks.get(0).getLocations()[0];
      cluster.stopDataNode(first.getName());

      //get checksum again
      final FileChecksum cs2 = fs.getFileChecksum(p);
      assertEquals(cs1, cs2);
    } finally {
      cluster.shutdown();
    }
  }
}