WaitCondition count should be updatable

[Clint Byrum]

Count should be extremely straight forward to update without replacing the entire wait condition.

[Steven Hardy (shardy)]

Can you explain the use-case here?

Since the count is only used while the wait condition is CREATE, IN_PROGRESS, updating it after it's CREATE, COMPLETE will have no practical use, surely?

[Clint Byrum (clint-fewbar)]

I am thinking about how updates should happen (not necessarily how they do happen now).

I suggest they should wait for waitconditions too. I guess CFN doesn't do that, but we will definitely need a resource that does all of what the cfn waitcondition does plus wait on updates for canary based rolling updates to work properly.

Anyway, a simpler use case that applies now is the autoscaling group problem raised by Simon Pasquier on openstack-dev

http://lists.openstack.org/pipermail/openstack-dev/2013-September/015205.html

Simon is changing a parameter that controls both the size of the instance group and the count expected in the waitcondition. This is causing the waitcondition to be replaced, but without cfn-hup the same number of signals do not arrive, and thus the stack is "stuck". Perhaps this just needs to be documented prominently and instance groups need to always be configured to use cfn-hup/os-collect-config to watch the count for changes.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/61218

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/61218
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=005b64ae30838a4a75078a5f52704690ce3077ef
Submitter: Jenkins
Branch: master

commit 005b64ae30838a4a75078a5f52704690ce3077ef
Author: Pablo Andres Fuente <email address hidden>
Date: Tue Dec 10 16:41:12 2013 -0300

    WaitCondition Count property is now updatable

    The Count property of WaitCondition resource was modified to be
    updatable.
    Now, when that property is updated, the WaitCondition and the associated
    WaitConditionHandle are no longer being regenerated.

    Change-Id: If234b7a1400ff1b2c17fc24c436d8f64f4b1fd88
    Closes-Bug: #1228362