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From "jiangyu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-9143) updateCountForQuota method during EditlogTailer loadEdit can make SNN timeout very often
Date Fri, 25 Sep 2015 08:57:04 GMT
jiangyu created HDFS-9143:
-----------------------------

             Summary: updateCountForQuota method during EditlogTailer loadEdit can make SNN
timeout very often 
                 Key: HDFS-9143
                 URL: https://issues.apache.org/jira/browse/HDFS-9143
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.6.0, 2.4.0
            Reporter: jiangyu
            Priority: Minor


I have seen many logs from datanodes in our cluster reporting socket timeout when sending
heartbeat or blockReceivedAndDeleted to Standby NameNode, but it never happen to Active NameNode.
 
At first, i thought it maybe caused by Editlog Tailer fetch Editlog too much making full gc,
but after i watched the gc log, it is not. So i investigate the code path and log, find it
only take very few seconds for the SNN to fetch the journal and merge it. But when you open
the webpage of SNN during merge processing, it can not response  like stop the world time
of full GC, but there is no gc at that time. So i jstack SNN for some time, and finding all
the time consumed by updateCountForQuota method in FSImage.  
The updateCountForQuota is called ervry time when loadEdits, it update the count of each directory
with quota in the namespace from ROOT, besides it hold the write lock of FSImage, so every
time when SNN merge the edit from JN, it is always making the stop world.  
I don't think it is necessary for SNN to updateCountForQuota everytime when tail the edit,
when trasition to Active, it call updateCountForQuota and never missing any quota data.



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