Open Stack

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.

To cope with this situation, I've found 2 options:
1/ declare 2 parameters in my template: nb of instances (N for creation, 
N+X for update) and count of wait conditions (N for creation, X for 
update). See [1] for the details.
2/ declare only one parameter in my template (the size of the group) and 
leverage cfn-hup on the existing instances to re-execute cfn-signal. See 
[2] for the details.

The solution 1 is not really user-friendly and I found that solution 2 
is a bit complicated. Does anybody know a simpler way to achieve the 
same result?

Regards,

[1] http://paste.openstack.org/show/47142/
[2] http://paste.openstack.org/show/47148/
-- 
Simon Pasquier
Software Engineer
Bull, Architect of an Open World
Phone: + 33 4 76 29 71 49
http://www.bull.com