[jira] [Comment Edited] (HBASE-16440) MemstoreChunkPool might cross its maxCount of chunks to pool

["Anoop Sam John (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-16440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15433201#comment-15433201 ] 

Anoop Sam John edited comment on HBASE-16440 at 8/23/16 5:00 PM:
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Pushed to master. (Fixed Ram's comment while push) Thanks for the reviews Ram and Stack.


was (Author: anoop.hbase):
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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