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From: Kevin Burton <burton@spinn3r.com>
Date: Sat, 20 Jun 2015 19:43:04 -0700
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 <CAAZU44mf9jg5uRS2jkM_tCJLkizG51rkYkb2oDNX7AeRGNJAZA@mail.gmail.com>
Subject: Re: Potential threading bug in MemoryMessageStore.
To: users@activemq.apache.org
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I didn=E2=80=99t.. it=E2=80=99s a race so if it=E2=80=99s happening is prob=
ably happening not that
often .  Maybe a test could be created to try to introduce the race.

On Thu, Jun 18, 2015 at 9:57 PM, Tim Bain <tbain@alumni.duke.edu> wrote:

> Did you look at this any further?  Looking at the code, it looks like the
> call will be protected without explicit synchronization by the intrinsic
> lock on the synchronizedMap (and I think that some other methods such as
> delete() and addMessage() that just call a method on the synchronizedMap
> could have their synchronized blocks removed), though I might be looking =
at
> that wrong.
>
> Tim
>
> On Mon, Apr 6, 2015 at 1:58 PM, Kevin Burton <burton@spinn3r.com> wrote:
>
> > Pretty sure getMessage() in MemoryMessageStore has a bug.
> >
> > All access to messageTable is synchronized.  this method is not.  This
> > means that there=E2=80=99s a race where a message can go into the queue=
 but the
> > thread reading it may have a cache copy of the data structure meaning i=
t
> > would get a cache miss
> >
> > Also, it looks like =E2=80=9CaddMessage=E2=80=9D is doubly synchronized=
.
> >
> >     public Message getMessage(MessageId identity) throws IOException {
> >         return messageTable.get(identity);
> >     }
> >
> > =E2=80=A6 I=E2=80=99m going to migrate to using a PriorityBlockingQueue=
 for this and
> remove
> > all the synchronization and will try to submit a patch. Also I think
> > PriorityBlockingQueue will lower memory usage by 40%
> >
> >
> > --
> >
> > Founder/CEO Spinn3r.com
> > Location: *San Francisco, CA*
> > blog: http://burtonator.wordpress.com
> > =E2=80=A6 or check out my Google+ profile
> > <https://plus.google.com/102718274791889610666/posts>
> > <http://spinn3r.com>
> >
>


--=20

Founder/CEO Spinn3r.com
Location: *San Francisco, CA*
blog: http://burtonator.wordpress.com
=E2=80=A6 or check out my Google+ profile
<https://plus.google.com/102718274791889610666/posts>

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