Open Stack

The more the better :)

If seriously, this one is less detailed and rather focuses on high-level things so that everyone can have a high-level understanding of what’s been going on on Mistral/TaskFlow integration. In other words, this email raises question “What” and doesn’t raise “Why?” while [0] goes deeper into details.

[0] http://lists.openstack.org/pipermail/openstack-dev/2014-April/032461.html

Renat Akhmerov
@ Mirantis Inc.



On 12 Apr 2014, at 00:59, Joshua Harlow <harlowja at yahoo-inc.com> wrote:

> I'm confused, why is this 2 emails??
> 
> http://lists.openstack.org/pipermail/openstack-dev/2014-April/032461.html
> 
> Seems better to just have 1 chain, not 2.
> 
> From: Dmitri Zimine <dz at stackstorm.com>
> Reply-To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org>
> Date: Friday, April 11, 2014 at 9:55 AM
> To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org>
> Subject: [openstack-dev] [Mistral][TaskFlow] Mistral-TaskFlow Summary
> 
>> We prototyped Mistral / TaskFlow integration and have a follow-up discussions. 
>> 
>> SUMMARY: Mistral (Workflow Service) can embed TaskFlow as a workflow library, with some required modifications to function resliently as a service, and for smooth integration. However, the TaskFlow flow controls are insufficient for Mistral use cases. 
>> 
>> Details discussed on other thirds. 
>> The prototype scope - [0]; code and discussion - [1] and techical highlights - [2].
>> 
>> DETAILS: 
>> 
>> 1) Embedding TaskFlow inside Mistral:
>> * Required: make the engine "lazy" [3], [4].This is required to support long-running delegates and not loose tasks when engine manager process restarts.
>> 
>> * Persistence: need clarity how to replace or mix-in TaskFlow persistence with Mistral persistence. Renat is taking a look.
>> 
>> * Declaring Flows in YAML DSL: done for simplest flow. Need to prototype for data flow. Rich flow controls are missing in TaskFlow for a representative prototype.
>> 
>> * ActionRunners vs Taskflow Workers - not prototyped. Not a risk: both Mistral and TaskFlow implementations work. But we shall resolve the overlap. 
>> 
>> * Ignored for now - unlikely any risks: Keystone integration, Mistral event scheduler, Mistral declarative services and action definition.
>> 
>> 2) TaskFlow library features
>> * Must: flow control - conditional transitions, references, expression evaluation, to express real-life workflows [5]. The required flow control primitives are 1) repeater 2) flow in flow 3) direct transition 4) conditional transition 5) multiple data. TaskFlow has 1) and 2), need to add 3/4/5. 
>> 
>> * Other details and smaller requests are in the discussion [1]
>> 
>> 3) Next Steps proposed:
>> * Mistal team: summarize the requirements discussed and agreed on [2] and [3]
>> * Mistral team: code sample (tests?) on how Mistral would like to consume TaskFlow lazy engine 
>> * Taskflow team: Provide a design for alternative TaskExecutor approach (prototypes, boxes, arrows, crayons :)) 
>> * Decide on lazy engine
>> * Move the discussion on other elements on integration.
>> 
>> References:
>> [0] The scope of the prototype: https://etherpad.openstack.org/p/mistral-taskflow-prototype
>> [1] Prototype code and discussion https://github.com/enykeev/mistral/pull/1
>> [2] Techical summary http://lists.openstack.org/pipermail/openstack-dev/2014-April/032461.html
>> [3] Email discussion on TaskFlow lazy eninge http://lists.openstack.org/pipermail/openstack-dev/2014-March/031134.html
>> [4] IRC discussion Mistral/Taskflow http://paste.openstack.org/show/75389/
>> [5] Use cases https://github.com/dzimine/mistral-workflows/tree/add-usecases
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