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From "nkeywal (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-5163) TestLogRolling#testLogRollOnDatanodeDeath fails sometimes on central build or hadoop QA on trunk ("The directory is already locked.")
Date Tue, 10 Jan 2012 00:43:45 GMT
TestLogRolling#testLogRollOnDatanodeDeath fails sometimes on central build or hadoop QA on
trunk ("The directory is already locked.")

                 Key: HBASE-5163
                 URL: https://issues.apache.org/jira/browse/HBASE-5163
             Project: HBase
          Issue Type: Bug
          Components: test
    Affects Versions: 0.94.0
         Environment: all
            Reporter: nkeywal
            Assignee: nkeywal
            Priority: Minor

The stack is typically:
    <error message="Cannot lock storage /tmp/19e3e634-8980-4923-9e72-a5b900a71d63/dfscluster_32a46f7b-24ef-488f-bd33-915959e001f4/dfs/data/data3.
The directory is already locked." type="java.io.IOException">java.io.IOException: Cannot
lock storage /tmp/19e3e634-8980-4923-9e72-a5b900a71d63/dfscluster_32a46f7b-24ef-488f-bd33-915959e001f4/dfs/data/data3.
The directory is already locked.
	at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.lock(Storage.java:602)
	at org.apache.hadoop.hdfs.server.common.Storage$StorageDirectory.analyzeStorage(Storage.java:455)
	at org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:111)
	at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:376)
	at org.apache.hadoop.hdfs.server.datanode.DataNode.&lt;init&gt;(DataNode.java:290)
	at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:1553)
	at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1492)
	at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:1467)
	at org.apache.hadoop.hdfs.MiniDFSCluster.startDataNodes(MiniDFSCluster.java:417)
	at org.apache.hadoop.hdfs.MiniDFSCluster.startDataNodes(MiniDFSCluster.java:460)
	at org.apache.hadoop.hbase.regionserver.wal.TestLogRolling.testLogRollOnDatanodeDeath(TestLogRolling.java:470)
        // ...

It can be reproduced without parallelization or without executing the other tests in the class.
It seems to fail about 5% of the time.

This comes from the naming policy for the directories in MiniDFSCluster#startDataNode. It
depends on the number of nodes *currently* in the cluster, and does not take into account
previous starts/stops:
   for (int i = curDatanodesNum; i < curDatanodesNum+numDataNodes; i++) {
      if (manageDfsDirs) {
        File dir1 = new File(data_dir, "data"+(2*i+1));
        File dir2 = new File(data_dir, "data"+(2*i+2));
      // [...]

This means that it if we want to stop/start a datanode, we should always stop the last one,
if not the names will conflict. This test exhibits the behavior:
  public void testMiniDFSCluster_startDataNode() throws Exception {

    assertTrue( dfsCluster.getDataNodes().size() == 2 );

    // Works, as we kill the last datanode, we can now start a datanode
      .startDataNodes(TEST_UTIL.getConfiguration(), 1, true, null, null);

    // Fails, as it's not the last datanode, the directory will conflict on
    //  creation
    try {
        .startDataNodes(TEST_UTIL.getConfiguration(), 1, true, null, null);
      fail("There should be an exception because the directory already exists");
    } catch (IOException e) {
      assertTrue( e.getMessage().contains("The directory is already locked."));
      LOG.info("Expected (!) exception caught " + e.getMessage());

    // Works, as we kill the last datanode, we can now restart 2 datanodes
    // This makes us back with 2 nodes
      .startDataNodes(TEST_UTIL.getConfiguration(), 2, true, null, null);

And then this behavior is randomly triggered in testLogRollOnDatanodeDeath because when we
DatanodeInfo[] pipeline = getPipeline(log);
assertTrue(pipeline.length == fs.getDefaultReplication());

and then kill the datanodes in the pipeline, we will have:
 - most of the time: pipeline = 1 & 2, so after killing 1&2 we can start a new datanode
that will reuse the available 2's directory.
 - sometimes: pipeline = 1 & 3. In this case,when we try to launch the new datanode, it
fails because it wants to use the same directory as the still alive '2'.

There are two ways of fixing the test:
1) Fix the naming rule in MiniDFSCluster#startDataNode, for example to ensure that the directory
names will not be reused. But I wonder if there is not a testCase somewhere (may be not in
HBase) depending on this behavior.
2) Kill explicitly the first and second datanode without using the pipeline to be sure that
the names won't conflict.

Feedback welcome and the choice to make here...

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