[jira] [Commented] (POOL-284) "Returned object not currently part of this pool" when using mutable objects

["Mark Thomas (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/POOL-284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14352951#comment-14352951 ] 

Mark Thomas commented on POOL-284:
----------------------------------

people.a.o has 48 cores for you to play with. That should be plenty (and is where I did some of my concurrecy testing for the Pool 2.x design).

> "Returned object not currently part of this pool" when using mutable objects
> ----------------------------------------------------------------------------
>
>                 Key: POOL-284
>                 URL: https://issues.apache.org/jira/browse/POOL-284
>             Project: Commons Pool
>          Issue Type: Bug
>    Affects Versions: 2.2
>            Reporter: Valentin Mayamsin
>         Attachments: StaticBucketMap-mods.patch, identityWrapper.patch, pool-283-4.patch
>
>
> I'm using pool to reuse expensive Sets (storing millions of items). Here is a test which fails:
> {code}
>         GenericObjectPoolConfig config = new GenericObjectPoolConfig ();
>         GenericObjectPool<Set> aPool = new GenericObjectPool<> ( new BasePooledObjectFactory<Set> ()
>         {
>             @Override
>             public Set create () throws Exception
>             {
>                 return new HashSet();
>             }
>             @Override
>             public PooledObject<Set> wrap ( Set o )
>             {
>                 return new DefaultPooledObject<> ( o );
>             }
>             @Override
>             public void passivateObject ( PooledObject<Set> p ) throws Exception
>             {
>                 p.getObject ().clear ();
>                 super.passivateObject ( p );
>             }
>         }, config );
>         Set set = aPool.borrowObject ();
>         set.add ( new Object () );
>         
>         aPool.returnObject ( set );
> {code}
> This is because GenericObjectPool uses a HashMap<Object, PooledObject> to correlate objects and state. HashMap stores objects correlated to their hashCode. So in case object's state change then hashCode will change, thus Map will fail to correlate this object since it stores old hashCode



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