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From "Alex Holmes (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-3061) Cached directory size in INodeDirectory can get permantently out of sync with computed size, causing quota issues
Date Thu, 08 Mar 2012 00:12:57 GMT
Cached directory size in INodeDirectory can get permantently out of sync with computed size,
causing quota issues
-----------------------------------------------------------------------------------------------------------------

                 Key: HDFS-3061
                 URL: https://issues.apache.org/jira/browse/HDFS-3061
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: name-node
    Affects Versions: 0.20.203.0
            Reporter: Alex Holmes


It appears that there's a condition under which a HDFS directory with a quota set can get
to a point where the cached size for the directory can permanently differ from the computed
value.  When this happens the following command:

{code}
hadoop fs -count -q /tmp/quota-test
{code}

results in the following output in the NameNode logs:

{code}
WARN org.apache.hadoop.hdfs.server.namenode.NameNode: Inconsistent diskspace for directory
quota-test. Cached: 6000 Computed: 6072
{code}

I've observed both transient and persistent instances of this happening.  In the transient
instances this warning goes away, but in the persistent instances every invocation of the
{{fs -count -q}} command yields the above warning.

I've seen instances where the actual disk usage of a directory is 25% of the cached value
in INodeDirectory, which creates problems since the quota code uses this cached value to determine
whether block write requests are permitted.

This isn't easy to reproduce - I am able to (inconsistently) get HDFS into this state with
a simple program which:

#  Writes files into HDFS
#  When a DSQuotaExceededException is encountered removes all files created in step 1
#  Repeat step 1

I'm going to try and come up with a more repeatable test case to reproduce this issue.

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