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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1332) When unable to place replicas, BlockPlacementPolicy should log reasons nodes were excluded
Date Wed, 11 May 2011 22:58:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13032157#comment-13032157
] 

Ted Yu commented on HDFS-1332:
------------------------------

I added a new test in TestDecommission:
{code}
  @Test
  public void testDecommissionForReasonableExceptionMsg() throws IOException {
    startCluster(1, 2, conf);
    FileSystem fileSys = cluster.getFileSystem(0);

    // Decommission one node. Verify that node is decommissioned.
    DatanodeInfo decomNode = decommissionNode(0, null,
        AdminStates.DECOMMISSIONED);
    Path file1 = new Path("testDecommission.dat");
    try {
      writeFile(fileSys, file1, 2);
    } catch (Exception nere) {
      String msg = nere.getMessage();
      assertTrue("Expected detail about not enough replicas",
          msg.contains("is not chosen"));
    }
  }
{code}
But the NotEnoughReplicasException is caught by chooseTarget().
At least I saw the following:
{code}
11/05/11 15:54:58 WARN namenode.FSNamesystem: Not able to place enough replicas, still in
need of 1 to reach 2
Not able to place enough replicas.[127.0.0.1:50055: Node /default-rack/127.0.0.1:50055 is
not chosen because the node is (being) decommissioned ]
{code}

> When unable to place replicas, BlockPlacementPolicy should log reasons nodes were excluded
> ------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1332
>                 URL: https://issues.apache.org/jira/browse/HDFS-1332
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: Todd Lipcon
>            Assignee: Ted Yu
>            Priority: Minor
>              Labels: newbie
>         Attachments: HDFS-1332.patch
>
>
> Whenever the block placement policy determines that a node is not a "good target" it
could add the reason for exclusion to a list, and then when we log "Not able to place enough
replicas" we could say why each node was refused. This would help new users who are having
issues on pseudo-distributed (eg because their data dir is on /tmp and /tmp is full). Right
now it's very difficult to figure out the issue.

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