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From "Rui Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8920) Erasure Coding: when recovering lost blocks, logs can be too verbose and hurt performance
Date Wed, 16 Sep 2015 05:35:46 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8920?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14746906#comment-14746906
] 

Rui Li commented on HDFS-8920:
------------------------------

I tried several failures locally and cannot reproduce them. Also both {{TestDFSInputStream}}
and {{TestDFSStripedInputStream}} pass on my side. So I suppose the failures here are not
related.

Since the patch only changes how we print logs, I didn't add new tests for it. I did manually
perform some tests on a cluster, as I mentioned above.

> Erasure Coding: when recovering lost blocks, logs can be too verbose and hurt performance
> -----------------------------------------------------------------------------------------
>
>                 Key: HDFS-8920
>                 URL: https://issues.apache.org/jira/browse/HDFS-8920
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Rui Li
>            Assignee: Rui Li
>         Attachments: HDFS-8920-HDFS-7285.1.patch
>
>
> When we test reading data with datanodes killed, {{DFSInputStream::getBestNodeDNAddrPair}}
becomes a hot spot method and effectively blocks the client JVM. This log seems too verbose:
> {code}
>     if (chosenNode == null) {
>       DFSClient.LOG.warn("No live nodes contain block " + block.getBlock() +
>           " after checking nodes = " + Arrays.toString(nodes) +
>           ", ignoredNodes = " + ignoredNodes);
>       return null;
>     }
> {code}



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