Open Stack

Hi Adrian,

On Mon, Mar 9, 2015 at 6:53 PM, Adrian Otto <adrian.otto at rackspace.com>
wrote:

> Magnum Team,
>
> In the following review, we have the start of a discussion about how to
> tackle bay status:
>
> https://review.openstack.org/159546
>
> I think a key issue here is that we are not subscribing to an event feed
> from Heat to tell us about each state transition, so we have a low degree
> of confidence that our state will match the actual state of the stack in
> real-time. At best, we have an eventually consistent state for Bay
> following a bay creation.
>
> Here are some options for us to consider to solve this:
>
> 1) Propose enhancements to Heat (or learn about existing features) to emit
> a set of notifications upon state changes to stack resources so the state
> can be mirrored in the Bay resource.
>

A drawback of this option is that it increases the difficulty of
trouble-shooting. In my experience of using Heat (SoftwareDeployments in
particular), Ironic and Trove, one of the most frequent errors I
encountered is that the provisioning resources stayed in deploying state
(never went to completed). The reason is that they were waiting a callback
signal from the provisioning resource to indicate its completion, but the
callback signal was blocked due to various reasons (e.g. incorrect firewall
rules, incorrect configs, etc.). Troubling-shooting such problem is
generally harder.


>
> 2) Spawn a task to poll the Heat stack resource for state changes, and
> express them in the Bay status, and allow that task to exit once the stack
> reaches its terminal (completed) state.
>
> 3) Don’t store any state in the Bay object, and simply query the heat
> stack for status as needed.


> Are each of these options viable? Are there other options to consider?
> What are the pro/con arguments for each?
>
> Thanks,
>
> Adrian
>
>
>
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