Horizon also needs the retry option. It solves a major problem specified in 
this blueprint: 
https://blueprints.launchpad.net/horizon/+spec/relaunch-failed-stack

Regards,
Nikunj


-----Original Message-----
From: Patil, Anant (HP Converged Cloud R&D)
Sent: Wednesday, January 14, 2015 5:54 PM
To: [email protected]
Subject: Re: [openstack-dev] [Heat] Precursor to Phase 1 Convergence

On 09-Jan-15 19:19, Zane Bitter wrote:
> On 09/01/15 01:07, Angus Salkeld wrote:
>> I am not in favor of the --continue as an API. I'd suggest responding
>> to resource timeouts and if there is no response from the task, then
>> re-start (continue) the task.
>
> Yeah, I am not in favour of a new API either. In fact, I believe we
> already have this functionality: if you do another update with the
> same template and parameters then it will break the lock and continue
> the update if the engine running the previous update has failed. And
> when we switch over to convergence it will still do the Right Thing
> without any extra implementation effort.
>
> There is one improvement we can make to the API though: in Juno, Ton
> added a PATCH method to stack update such that you can reuse the
> existing parameters without specifying them again. We should extend
> this to the template also, so you wouldn't have to supply any data to
> get Heat to start another update with the same template and parameters.
>
> I'm not sure if there is a blueprint for this already; co-ordinate
> with Ton if you are planning to work on it.
>
> cheers,
> Zane.
>
> _______________________________________________
> OpenStack-dev mailing list
> [email protected]<mailto:[email protected]>
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>
IMHO, there are two different things here:

1. Failures external to Heat engine (or out-of-band failures). A convenient way 
to issue a stack-update on a stack that fails due to out-of-band failures is 
needed. When a stack fails due to service unavailability or infrastructure 
issues, operators/admins can fix those issues and then re-start the 
provisioning or tell users to restart.
Currently, it is done by issuing a stack-update on the failed stack.  It will 
be convenient to have an option to the stack-update command to retry the stack 
operation without having to specify the templates and parameters + environment 
again. User shouldn't need to supply any data again to start the update of 
failed stack.

Folks working in Horizon would definitely need something like this.
Horizon UI need not save a local copy of template and parameter + environment 
supplied by user, but rely on Heat because Heat already has the data. It would 
be convenient for Horizon to issue a --retry for stack-create or stack-update 
when the stack fails due to external problems that the operators/users fix.

2. Internal failures (or Heat engine failing). Continuing a stack operation 
even after a Heat engine fails due to internal error. I think Vishnu is talking 
about this part. When an engine fails, other engines should be able to take up 
the task of provisioning the stack without any user intervention. No new API or 
any option to stack-create or update is needed. Something like a periodic timer 
is needed to check if the engine provisioning a stack is up. If not, the lock 
is stolen and stack is restarted... may be by again issuing stack-update with 
same template and parameters. This is like an interim solution to continuous 
observer...the stack timer would periodically check for stacks that are "stuck" 
because the engine failed and issue another update or something equivalent to 
proceed with other Heat engines. Or as a first step, like Steve said, put the 
stack to FAILED state and let user initiate a stack-update (probably with the 
option specified 1).

Please share your thoughts.

- Anant

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