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From "Wei-Chiu Chuang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12182) BlockManager.metaSave does not distinguish between "under replicated" and "missing" blocks
Date Fri, 21 Jul 2017 19:53:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16096759#comment-16096759
] 

Wei-Chiu Chuang commented on HDFS-12182:
----------------------------------------

Hi [~wchevreuil] thanks for reporting the issue and posting the patch.

For correctness, the new code added should be in the synchronized block
{code}
synchronized (neededReconstruction) {
  ...
}
{code}

Would it be possible to add a test?

> BlockManager.metaSave does not distinguish between "under replicated" and "missing" blocks
> ------------------------------------------------------------------------------------------
>
>                 Key: HDFS-12182
>                 URL: https://issues.apache.org/jira/browse/HDFS-12182
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs
>            Reporter: Wellington Chevreuil
>            Assignee: Wellington Chevreuil
>            Priority: Trivial
>              Labels: newbie
>             Fix For: 3.0.0-alpha3
>
>         Attachments: HDFS-12182.001.patch
>
>
> Currently, *BlockManager.metaSave* method (which is called by "-metasave" dfs CLI command)
reports both "under replicated" and "missing" blocks under same metric *Metasave: Blocks waiting
for reconstruction:* as shown on below code snippet:
> {noformat}
>    synchronized (neededReconstruction) {
>       out.println("Metasave: Blocks waiting for reconstruction: "
>           + neededReconstruction.size());
>       for (Block block : neededReconstruction) {
>         dumpBlockMeta(block, out);
>       }
>     }
> {noformat}
> *neededReconstruction* is an instance of *LowRedundancyBlocks*, which actually wraps
5 priority queues currently. 4 of these queues store different under replicated scenarios,
but the 5th one is dedicated for corrupt/missing blocks. 
> Thus, metasave report may suggest some corrupt blocks are just under replicated. This
can be misleading for admins and operators trying to track block missing/corruption issues,
and/or other issues related to *BlockManager* metrics.
> I would like to propose a patch with trivial changes that would report corrupt blocks
separately.



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