[openstack-dev] [Mistral] Proposal for the Resume Feature

W Chan m4d.coder at gmail.com
Mon Jun 15 23:51:01 UTC 2015

Resending to see if this fixes the formatting for outlines below.

I want to continue the discussion on the workflow "resume" feature.

Resuming from our last conversation @
I don't think we should limit how users resume. There may be different
possible scenarios. User can fix the environment or condition that led to
the failure of the current task and the user wants to just re-run the
failed task.  Or user can actually fix the environment/condition which
include fixing what the task was doing, then just want to continue the next
set of task(s).

The following is a list of proposed changes.

1. A new CLI operation to resume WF (i.e. mistral workflow-resume).

    A. If no additional info is provided, assume this WF is manually paused
and there are no task/action execution errors. The WF state is updated to
RUNNING. Update using the put method @ ExecutionsController. The put method
checks that there's no task/action execution errors.

    B. If WF is in an error state

        i. To resume from failed task, the workflow-resume command requires
the WF execution ID, task name, and/or task input.

        ii. To resume from failed with-items task

            a. Re-run the entire task (re-run all items) requires WF
execution ID, task name             and/or task input.

            b. Re-run a single item requires WF execution ID, task name,
with-items index, and/or task input for the item.

            c. Re-run selected items requires WF execution ID, task name,
with-items indices, and/or task input for each items.

                - To resume from the next task(s), the workflow-resume
command requires the WF execution ID, failed task name, output for the
failed task, and a flag to skip the failed task.

2. Make ERROR -> RUNNING as valid state transition @ is_valid_transition

3. Add a comments field to Execution model. Add a note that indicates the
execution is launched by workflow-resume. Auto-populated in this case.

4. Resume from failed task.

    A. Re-run task with the same task inputs >> POST new action execution
for the task execution @ ActionExecutionsController

    B. Re-run task with different task inputs >> POST new action execution
for the task execution, allowed for different input @

5. Resume from next task(s).

    A. Inject a noop task execution or noop action execution (undecided
yet) for the failed task with appropriate output.  The spec is an adhoc
spec that copies conditions from the failed task. This provides some audit
functionality and should trigger the next set of task executions (in case
of branching and such).
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