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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2052) FSNamesystem should not sync the log with the write lock held
Date Fri, 24 Jun 2011 21:49:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13054697#comment-13054697
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Suresh Srinivas commented on HDFS-2052:
---------------------------------------

I realized we are talking about two things here. Description mainly talks about editlog. Your
later comments are talking about audit log. Why is audit log important here? For example,
rename does not do auditlog when you overwrite the existing file in rename.

> FSNamesystem should not sync the log with the write lock held
> -------------------------------------------------------------
>
>                 Key: HDFS-2052
>                 URL: https://issues.apache.org/jira/browse/HDFS-2052
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: Eli Collins
>
> FSNamesystem#deleteInternal releases the write lock before syncing the log, however FSNamesystem#startFileInternal
calls delete -> deleteInternal with the write lock held, which means deleteInternal will
sync the log while holding the lock. We could fix cases like this by passing  a flag indicating
whether the function should sysnc (eg in this case the sysnc is not necessary because startFileInternals
callers will sync the log) or modify the current calls to sync to flag that a sync is necessary
before returning to the caller rather than doing the sync right at the call sight. This way
the cost of syncing the log could be amortized over multiple function calls (and potentially
multiple RPCs if we didn't mind introducing some synchronization).

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