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<p class="MsoNormal">Hi all,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">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"><o:p> </o:p></p>
<p class="MsoNormal">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"><o:p> </o:p></p>
<p class="MsoNormal">To overcome this, we will need the following capability:<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l2 level1 lfo2"><![if !supportLists]><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Resource timeout (can be used for retry)<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l2 level1 lfo2"><![if !supportLists]><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Recover from engine failure (loss of stack timeout, resource action notification)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Suggestion:<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Use task queue like celery to host timeouts for both stack and resource.<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>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 class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Migrate heat to use TaskFlow. (Too many code change)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">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"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Your thoughts.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-Vishnu<o:p></o:p></p>
<p class="MsoNormal">IRC: ckmvishnu<o:p></o:p></p>
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