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From "Zhihong Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6322) Unnecessary creation of finalizers in HTablePool
Date Thu, 05 Jul 2012 00:20:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13406792#comment-13406792
] 

Zhihong Ted Yu commented on HBASE-6322:
---------------------------------------

Looks like we can add the following to HTableInterface in trunk:
{code}
  public NavigableMap<HRegionInfo, ServerName> getRegionLocations() throws IOException
{
{code}
so that RegionsResource can use it instead of getRegionsInfo().
And we don't need a cast in getTableRegions().
                
> Unnecessary creation of finalizers in HTablePool
> ------------------------------------------------
>
>                 Key: HBASE-6322
>                 URL: https://issues.apache.org/jira/browse/HBASE-6322
>             Project: HBase
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 0.92.0, 0.92.1, 0.94.0
>            Reporter: Ryan Brush
>             Fix For: 0.92.2
>
>         Attachments: HBASE-6322-0.92.1.patch, HBASE-6322-trunk.1.patch
>
>
> From a mailing list question:
> While generating some load against a library that makes extensive use of HTablePool in
0.92, I noticed that the largest heap consumer was java.lang.ref.Finalizer.  Digging in, I
discovered that HTablePool's internal PooledHTable extends HTable, which instantiates a ThreadPoolExecutor
and supporting objects every time a pooled HTable is retrieved.  Since ThreadPoolExecutor
has a finalizer, it and its dependencies can't get garbage collected until the finalizer runs.
 The result is by using HTablePool, we're creating a ton of objects to be finalized that are
stuck on the heap longer than they should be, creating our largest source of pressure on the
garbage collector.  It looks like this will also be a problem in 0.94 and trunk.
> The easy fix is just to have PooledHTable implement HTableInterface (rather than subclass
HTable), but this does break a unit test that explicitly checks that PooledHTable implements
HTable -- I can only assume this test is there for some historical passivity reason.

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