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From Afkham Azeez <afk...@gmail.com>
Subject Re: Cause of Scale Down Logic Issue was Identified
Date Fri, 18 Apr 2014 04:26:31 GMT
On Fri, Apr 18, 2014 at 1:12 AM, Imesh Gunaratne <imesh@apache.org> wrote:

> Hi,
>
> During last few days we noticed an intermittent issue in scale down logic
> and it was reported in STRATOS-614.
>
> Today after doing some thorough tests we identified the cause of this
> issue. The problem was with the topology event receiver queue. Since this
> queue was designed as a singleton,
>

Singletons should be avoided as much as possible, and used with caution.
Some even consider it an anti-pattern.


> it was being shared among multiple event receivers in Single JVM mode. As
> a result event messages were unevenly being dequeued to message processors
> and some event receivers were missing events randomly.
>
> This problem was also there in Tenant event receiver, Health Stat event
> receiver and Instance Notifier event receiver. I have now fixed this by
> introducing a message queue for each event receiver instance created.
>
> I have now committed this fix to master branch. Will do few more flow
> tests to verify the correction and update with the results soon.
>
> Thanks
>
> --
> Imesh Gunaratne
>
> Technical Lead, WSO2
> Committer & PPMC Member, Apache Stratos
>



-- 
*Afkham Azeez*
Director of Architecture; WSO2, Inc.; http://wso2.com,
*Member; Apache Software Foundation;
**http://www.apache.org/*<http://www.apache.org/>

*email: **azeez@wso2.com* <azeez@wso2.com>
* cell: +94 77 3320919 blog: **http://blog.afkham.org*<http://blog.afkham.org>
*twitter: **http://twitter.com/afkham_azeez*<http://twitter.com/afkham_azeez>
* linked-in: **http://lk.linkedin.com/in/afkhamazeez
<http://lk.linkedin.com/in/afkhamazeez>*

*Lean . Enterprise . Middleware*

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