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From "ryan rawson (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-1740) ICV has a subtle race condition only visible under high load
Date Tue, 04 Aug 2009 00:01:15 GMT
ICV has a subtle race condition only visible under high load
------------------------------------------------------------

                 Key: HBASE-1740
                 URL: https://issues.apache.org/jira/browse/HBASE-1740
             Project: Hadoop HBase
          Issue Type: Bug
    Affects Versions: 0.20.0
            Reporter: ryan rawson
             Fix For: 0.20.0, 0.20.1


ICV demonstrates a race condition under high load.  The result is a duplicate KeyValue with
the same timestamp, at first in the memcache, and in hfile, then both in hfile.  The get/scan
code doesnt know which one to read, and picks one arbitrarily.  One of the keyvalues is correct,
one is incorrect.

What happens at a deeper level:
- we start an ICV
- a snapshot happens and moves the memstore to the snapshot
- the ICV code puts a key-value into memstore that has the same timestamp as a keyvalue in
the snapshot.

This is a deep race condition and several attempts to fix it failed in production here at
SU.  This issue is about a more permanent fix.

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