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Date: Sat, 27 Jul 2013 06:49:52 +0000 (UTC)
From: "Lars Hofhansl (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12651358.1370532277170.123246.1374907792839@arcas>
In-Reply-To: <JIRA.12651358.1370532277170@arcas>
References: <JIRA.12651358.1370532277170@arcas>
Subject: [jira] [Commented] (HBASE-8698) potential thread creation in
 MetaScanner.metaScan
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    [ https://issues.apache.org/jira/browse/HBASE-8698?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13721551#comment-13721551 ] 

Lars Hofhansl commented on HBASE-8698:
--------------------------------------

0.94 test run:
{quote}
Results :

Failed tests:   testDeleteEditUnknownColumnFamilyAndOrTable(org.apache.hadoop.hbase.client.TestAdmin)

Tests run: 1359, Failures: 1, Errors: 0, Skipped: 13
{quote}

Ran TestAdmin a few times in a loop:
{quote}
Running org.apache.hadoop.hbase.client.TestAdmin
Tests run: 42, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 311.167 sec

Results :

Tests run: 42, Failures: 0, Errors: 0, Skipped: 0
{quote}

Going to commit this tomorrow.
                
> potential thread creation in MetaScanner.metaScan
> -------------------------------------------------
>
>                 Key: HBASE-8698
>                 URL: https://issues.apache.org/jira/browse/HBASE-8698
>             Project: HBase
>          Issue Type: Bug
>          Components: Client
>    Affects Versions: 0.94.7
>            Reporter: Kireet Reddy
>            Assignee: Lars Hofhansl
>             Fix For: 0.98.0, 0.95.2, 0.94.11
>
>         Attachments: 8698-0.94.txt, 8698-0.94-v2.txt, 8698-trunk.txt, 8698-trunk-v2.txt, 8698-trunk-v3.txt
>
>
> MetaScanner.metaScan() creates an instance of HTable per call. The constructur used creates a new ThreadPoolExecutor. The executor itself will not create a thread unless it's pool is used. I am not sure if the HTable instance in question ever uses it's pool. But if so, this could become a big performance issue. Logging an issue at Lars's request. mail list chain below.
> ------------------------------------- 
> Indeed. That is bad.
> I cannot see a clean fix immediately, but we need to look at this.
> Mind filing a ticket, Kireet?
> -- Lars
> ________________________________
>  From: Kireet <kireet-Teh5dPVPL8nQT0dZR+AlfA@public.gmane.org>
> To: public-user-50Pas4EWwPEyzMRdD/IqWQ-wOFGN7rlS/M9smdsby/KFg@public.gmane.org 
> Sent: Friday, May 31, 2013 11:58 AM
> Subject: Re: HConnectionManager$HConnectionImplementation.locateRegionInMeta
>  
> Even if I initiate the call via a pooled htable, the MetaScanner seems 
> to use a concrete HTable instance. The constructor invoked seems to 
> create a java ThreadPoolExecutor. I am not 100% sure but I think as long 
> as nothing is submitted to the ThreadPoolExecutor it won't create any 
> threads. I just wanted to confirm this was the case. I do see the 
> connection is shared.
> --Kireet
> On 5/30/13 7:38 PM, Ted Yu wrote:
> > HTablePool$**PooledHTable is a wrapper around HTable.
> >
> > Here is how HTable obtains a connection:
> >
> >     public HTable(Configuration conf, final byte[] tableName, final
> > ExecutorService pool)
> >         throws IOException {
> >       this.connection = HConnectionManager.getConnection(conf);
> >
> > Meaning the connection is a shared one based on certain key/value pairs
> > from conf.
> >
> > bq. So every call to batch will create a new thread?
> >
> > I don't think so.
> >
> > On Thu, May 30, 2013 at 11:28 AM, Kireet <kireet-Teh5dPVPL8nQT0dZR+AlfA-XMD5yJDbdMReXY1tMh2IBg@public.gmane.org> wrote:
> >
> >>
> >>
> >> Thanks, will give it a shot. So I should download 0.94.7 (latest stable)
> >> and run the patch tool on top with the backport? This is a little new to me.
> >>
> >> Also, I was looking at the stack below. From my reading of the code, the
> >> HTable.batch() call will always cause the prefetch call to occur, which
> >> will cause a new HTable object to get created. The constructor used in
> >> creating a new thread pool. So every call to batch will create a new
> >> thread? Or the HTable's thread pool never gets used as the pool is only
> >> used for writes? I think I am missing something but just want to confirm.
> >>
> >> Thanks
> >> Kireet

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