Open Stack

Hi Clint,

Thanks for the reply! I'll update the bug you raised with more 
information. In the meantime, I agree with you that cfn-hup is enough 
for now.

BTW, is there any bug or missing feature that would prevent me from 
replacing cfn-hup by os-collect-config?

Simon

Le 20/09/2013 22:12, Clint Byrum a écrit :
> Excerpts from Simon Pasquier's message of 2013-09-17 05:57:58 -0700:
>> Hello,
>>
>> I'm testing stack updates with instance group and wait conditions and
>> I'd like to get feedback from the Heat community.
>>
>> My template declares an instance group resource with size = N and a wait
>> condition resource with count = N (N being passed as a parameter of the
>> template). Each group's instance is calling cfn-signal (with a different
>> id!) at the end of the user data script and my stack creates with no error.
>>
>> Now when I update my stack to run N+X instances, the instance group gets
>> updated with size=N+X but since the wait condition is deleted and
>> recreated, the count value should either be updated to X or my existing
>> instances should re-execute cfn-signal.
>
> That is a bug, the count should be something that can be updated in-place.
>
> https://bugs.launchpad.net/heat/+bug/1228362
>
> Once that is fixed, there will be an odd interaction between the groups
> though. Any new instances will add to the count, but removed instances
> will not decrease it. I'm not sure how to deal with that particular quirk.
>
> That said, rolling updates will likely produce some changes to the way
> updates interact with wait conditions so that we can let instances and/or
> monitoring systems feed back when an instance is ready. That will also
> help deal with the problem you are seeing.
>
> In the mean time, cfn-hup is exactly what you want, and I see no problem
> with re-running cfn-signal after an update to signal that the update
> has applied.
>
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-- 
Simon Pasquier
Software Engineer
Bull, Architect of an Open World
Phone: + 33 4 76 29 71 49
http://www.bull.com