[openstack-dev] [Mistral] really simple workflow for Heat configuration tasks

Thomas Spatzier thomas.spatzier at de.ibm.com
Tue Nov 12 12:04:00 UTC 2013

Hi Angus,

that is an interesting idea. Since you mentioned the software config
proposal in the beginning as a related item, I guess you are trying to
solve some software config related issues with Mistral. So a few questions,
looking at this purely from a software config perspect:

Are you thinking about doing the infrastructure orchestration (VMs,
volumes, network etc) with Heat's current capabilities and then let the
complete software orchestration be handled by Mistral tasks? I.e. bootstrap
the workers on each VM and have the definition of when which agent does
something defined in a flow?

If yes, is there a way for passing data around - e.g. output produced by
one software config step is input for another software config step?

Again, if my above assumption is true, couldn't there be problems when we
having two ways of doing orchestration, when the software layer thing would
take the Heat engine out of some processing and take away some control? Or
are you thinking about using Mistral as a general mechanism for task
execution in Heat, which would then probably resolve the conflict?


Angus Salkeld <asalkeld at redhat.com> wrote on 12.11.2013 02:15:15:
> From: Angus Salkeld <asalkeld at redhat.com>
> To: openstack-dev at lists.openstack.org,
> Date: 12.11.2013 02:18
> Subject: [openstack-dev] [Mistral] really simple workflow for Heat
> configuration tasks
> Hi all
> I think some of you were at the Software Config session at summit,
> but I'll link the ideas that were discussed:
> https://wiki.openstack.org/wiki/Heat/Blueprints/hot-software-config-WIP
> https://wiki.openstack.org/wiki/Heat/Blueprints/hot-software-config
> To me the basics of it are:
> 1. we need an entity/resource to place the configuration (in Heat)
> 2. we need a resource to install the configuration
>     (basically a task in Mistral)
> A big issue to me is the conflict between heat's taskflow and the new
> external one. What I mean by conflict is that it will become tricky
> to manage two parallel taskflow instances in one stack.
> This could be solved by:
> 1: totally using mistral (only use mistral workflow)
> 2: use a very simple model of just asking mistral to run tasks (no
>     workflow) this allows us to use heat's workflow
>     but mistral's task runner.
> Given that mistral has no real implementation yet, "2" would seem
> reasonable to me. (I think Heat developers are open to "1" when
> Mistral is more mature.)
> How could we use Mistral for config installation?
> -------------------------------------------------
> 1. We have a resource type in Heat that creates tasks in a Mistral
>     workflow (manual workflow).
> 2. Heat pre-configures the server to have a Mistral worker
>     installed.
> 3. the Mistral worker pulls tasks from the workflow and passes them
>     to an agent that can run it. (the normal security issues jump up
>     here - giving access to the taskflow from a guest).
> To do this we need an api that can add tasks to a workflow dynamically.
> like this:
> - create a simple workflow
> - create and run task A [run on server X]
> - create and run task B [run on server Y]
> - create and run task C [run on server X]
> (note: the task is run and completes before the next is added if there
>         is a dependancy, if tasks can be run in parallel then we add
>         tasks)
> The api could be something like:
> CRUD <mistral>/workflows/
> CRUD <mistral>/workflows/<wf>/tasks
> One thing that I am not sure of is how a server(worker) would know if a
> was for it or not.
> - perhaps we have a capability property of the task that we can use
>    (capablitiy[server] = <server-id>) or actually specify the worker we
>    want.
> I think this would be a good starting point for Mistral as it is a
> very simple but concrete starting point. Also if this is not done in
> Mistral we will have to add this in Heat (lets rather have it where
> it should be). This will also give us a chance to have confidence
> with Mistral before trying to do more complex workflows.
> If you (Heat and Mistral developers) are open to this we can discuss
> what needs to be done. I am willing to help with implementation.
> Thanks
> -Angus
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