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Re: non-trivial finalize() on AbstractJdbc2Statement

From: Imran <imranbohoran(at)gmail(dot)com>
To: Dave Cramer <pg(at)fastcrypt(dot)com>
Cc: pgsql-jdbc(at)postgresql(dot)org
Subject: Re: non-trivial finalize() on AbstractJdbc2Statement
Date: 2012-02-13 13:02:15
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-jdbc
Hi Dave

Thanks for your response. I agree that this might not be widespread. And I
haven't seen much mentions around this problem (hitting GC issues due to
non-trivial finalize() methods) reported (based on my google searches).
However, I guess the existence of it does provide the opportunity for this
to happen as we've noticed. IMHO, encouraging clients to use the api
as recommended (i.e. closing resources once they are done with them) is
better than the driver allowing opportunity for bad things to happen. Or
perhaps the driver caters to this kind of situation using WeakReference as
oppose to using a non-trivial finalize().

What are your thoughts?

-- Imran

On Mon, Feb 13, 2012 at 12:09 PM, Dave Cramer <pg(at)fastcrypt(dot)com> wrote:

> Well this is a typical which is worse case scenario. People leaking
> resources because they don't explicitly close them, or your case ? I'm
> not sure which is worse.
> Given that the driver is being used in many very high throughput sites
> without this problem, I'm curious as to why nobody else has complained
> Dave Cramer
> dave.cramer(at)credativ(dot)ca
> On Fri, Feb 10, 2012 at 12:39 PM, Imran <imranbohoran(at)gmail(dot)com> wrote:
> > Hello
> >
> > We've been having OOM errors in our applications through GC overhead
> limits
> > under heave load resources running queries. Inspecting the heap dump, it
> > appears that the finalizer queue is taken up most of the heap space.
> Almost
> > all of the the finalizer objects I've seen seem to have a
> > jdbc3PreparedStatement object in it. Going through the source code of the
> > driver I see that the 'AbstractJdbc2Statement' has a non-trivial finalize
> > method. I guess this explains why these objects end up in the finalizer
> > queue. Can I clarify the need to having this finalize() method here? It
> > seems to be calling the close() method of the statement which I would
> have
> > thought is the responsibility of the client building a Statement object.
> Is
> > there any chance this can be dropped so we don't see these objects
> ending up
> > in the finalizer queue under heavy load and the jvm running out of memory
> > before the GC threads gets around to 'actually' reclaim the memory?
> >
> > Also we are using postgres 9.0.4 and the 8.3-604.jdbc3 version of the
> > postgresql jdbc driver.
> >
> > Cheers
> > -- Imran

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Next:From: Vitalii TymchyshynDate: 2012-02-13 13:28:18
Subject: Re: non-trivial finalize() on AbstractJdbc2Statement
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