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From "Arpit Agarwal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10713) Throttle FsNameSystem lock warnings
Date Tue, 06 Sep 2016 19:15:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15468265#comment-15468265
] 

Arpit Agarwal commented on HDFS-10713:
--------------------------------------

Thanks for the updated patch [~hanishakoneru]. The read lock is not exclusive so the following
sequence of operations in readUnlock won't see a consistent state. This block of code probably
needs to synchronize on a separate mutex after releasing the read lock. 

{code}
    if (needReport && readLockInterval >= this.readLockReportingThreshold) {
      if (readLockInterval > longestReadLockHeldInterval) {
        longestReadLockHeldInterval = readLockInterval;
      }
      if (currentTime - timeStampOfLastReadLockReport > this
          .lockSuppressWarningInterval) {
        logReport = true;
        numSuppressedWarnings = numReadLockWarningsSuppressed;
        numReadLockWarningsSuppressed = 0;
        longestLockHeldInterval = longestReadLockHeldInterval;
        longestReadLockHeldInterval = 0;
        timeStampOfLastReadLockReport = currentTime;
      } else {
        numReadLockWarningsSuppressed++;
      }
    }

    this.fsLock.readLock().unlock();
{code}

I also had some questions about the _needReport_ logic I posted on HDFS-10817.

> Throttle FsNameSystem lock warnings
> -----------------------------------
>
>                 Key: HDFS-10713
>                 URL: https://issues.apache.org/jira/browse/HDFS-10713
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: logging, namenode
>            Reporter: Arpit Agarwal
>            Assignee: Hanisha Koneru
>         Attachments: HDFS-10713.000.patch, HDFS-10713.001.patch, HDFS-10713.002.patch,
HDFS-10713.003.patch
>
>
> The NameNode logs a message if the FSNamesystem write lock is held by a thread for over
1 second. These messages can be throttled to at one most one per x minutes to avoid potentially
filling up NN logs. We can also log the number of suppressed notices since the last log message.



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