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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Parallel worker was what I initially thought. But what to do if the engine hosting that worker goes down?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Vishnu<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> Angus Salkeld [mailto:asalkeld@mirantis.com]
<br>
<b>Sent:</b> Thursday, November 13, 2014 5:22 PM<br>
<b>To:</b> OpenStack Development Mailing List (not for usage questions)<br>
<b>Subject:</b> Re: [openstack-dev] [Heat] Using Job Queues for timeout ops<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Thu, Nov 13, 2014 at 6:29 PM, Murugan, Visnusaran <<a href="mailto:visnusaran.murugan@hp.com" target="_blank">visnusaran.murugan@hp.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi all,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Convergence-POC distributes stack operations by sending resource actions over RPC for any heat-engine to execute. Entire stack lifecycle will be controlled by worker/observer notifications.
This distributed model has its own advantages and disadvantages.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Any stack operation has a timeout and a single engine will be responsible for it. If that engine goes down, timeout is lost along with it. So a traditional way is for other engines
to recreate timeout from scratch. Also a missed resource action notification will be detected only when stack operation timeout happens.
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">To overcome this, we will need the following capability:<o:p></o:p></p>
<p>1.<span style="font-size:7.0pt"> </span>Resource timeout (can be used for retry)<o:p></o:p></p>
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<p class="MsoNormal">We will shortly have a worker job, can't we have a job that just sleeps that gets started in parallel with the job that is doing the work?<o:p></o:p></p>
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<p class="MsoNormal">It gets to the end of the sleep and runs a check. <o:p></o:p></p>
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<p>2.<span style="font-size:7.0pt"> </span>Recover from engine failure (loss of stack timeout, resource action notification)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">My suggestion above could catch failures as long as it was run in a different process.<o:p></o:p></p>
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<p class="MsoNormal">-Angus<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Suggestion:<o:p></o:p></p>
<p>1.<span style="font-size:7.0pt"> </span>Use task queue like celery to host timeouts for both stack and resource.<o:p></o:p></p>
<p>2.<span style="font-size:7.0pt"> </span>Poll database for engine failures and restart timers/ retrigger resource retry (IMHO: This would be a traditional and weighs heavy)<o:p></o:p></p>
<p>3.<span style="font-size:7.0pt"> </span>Migrate heat to use TaskFlow. (Too many code change)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I am not suggesting we use Task Flow. Using celery will have very minimum code change. (decorate appropriate functions)
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Your thoughts.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">-Vishnu<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">IRC: ckmvishnu<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
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<a href="http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev" target="_blank">http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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