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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-16440) MemstoreChunkPool might cross its maxCount of chunks to pool
Date Tue, 23 Aug 2016 17:00:26 GMT

     [ https://issues.apache.org/jira/browse/HBASE-16440?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Anoop Sam John updated HBASE-16440:
-----------------------------------
      Resolution: Fixed
    Hadoop Flags: Reviewed
          Status: Resolved  (was: Patch Available)

Pushed to master. Thanks for the reviews Ram and Stack.

> MemstoreChunkPool might cross its maxCount of chunks to pool
> ------------------------------------------------------------
>
>                 Key: HBASE-16440
>                 URL: https://issues.apache.org/jira/browse/HBASE-16440
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 2.0.0
>
>         Attachments: HBASE-16440.patch, HBASE-16440_V2.patch, HBASE-16440_V3.patch
>
>
> {code}
> void putbackChunks(BlockingQueue<Chunk> chunks) {
>     int maxNumToPutback = this.maxCount - reclaimedChunks.size();
>     if (maxNumToPutback <= 0) {
>       return;
>     }
>     chunks.drainTo(reclaimedChunks, maxNumToPutback);
>     // clear reference of any non-reclaimable chunks
>     if (chunks.size() > 0) {
>       if (LOG.isTraceEnabled()) {
>         LOG.trace("Left " + chunks.size() + " unreclaimable chunks, removing them from
queue");
>       }
>       chunks.clear();
>     }
>   }
> {code}
> There is no synchroization. 2 threads might be calling this API as part of a MSLAB close.
(Once the memstore is flushed). It pass all the chunks used by it.  (Those might  not have
been come from pool also).  We try to put back chunks such that it is not crossing maxCount.
  Suppose maxCount is 10 and currently no chunks in 'reclaimedChunks'. Say both threads at
line one. Both see 'maxNumToPutback ' as 10 and that will make 20 chunks being pooled.  Similar
issue is in putbackChunk(Chunk chunk) API also.



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