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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1112) Edit log buffer should not grow unboundedly
Date Fri, 14 May 2010 00:43:43 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12867332#action_12867332
] 

Hairong Kuang commented on HDFS-1112:
-------------------------------------

It turns out that the edit output stream for backup NN does not serialize edit logs when an
edit log entry is written. So there is no way to implement getUnflushedDataLen(). Here is
a minor change to the proposal. Instead, add a method boolean isTimeToSync() to EditLogOutputStream.
isTimeToSync() allows each edit stream to implement its own automatic sync policy, either
by size or by time. By default, no automatic sync is supported. EditLogOutputStream returns
true when the buffered data length is greater than the initial size.

> Edit log buffer should not grow unboundedly
> -------------------------------------------
>
>                 Key: HDFS-1112
>                 URL: https://issues.apache.org/jira/browse/HDFS-1112
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.22.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.22.0
>
>
> Currently HDFS does not impose an upper limit on the edit log buffer. In case there are
a large number of open operations coming in with access time update on, since open does not
call sync automatically, there is a possibility that the buffer grow to a large size, therefore
causes memory leak and full GC in extreme cases as described in HDFS-1104. 
> The edit log buffer should be automatically flushed when the buffer becomes full.

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