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From: Tim Bain <tbain@alumni.duke.edu>
Date: Thu, 18 Jun 2015 22:57:43 -0600
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Subject: Re: Potential threading bug in MemoryMessageStore.
To: ActiveMQ Users <users@activemq.apache.org>
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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 b=
ut the
> thread reading it may have a cache copy of the data structure meaning it
> 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 f=
or 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>
>

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