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From "Ryan Brush (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-6322) Unnecessary creation of finalizers in HTablePool
Date Tue, 03 Jul 2012 21:36:34 GMT

     [ https://issues.apache.org/jira/browse/HBASE-6322?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ryan Brush updated HBASE-6322:
------------------------------

    Description: 
>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.

  was:
>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.

    
> 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
>
> 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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