openstack/deb-python-taskflow
Code Issues Proposed changes

Merge "Add a suspension engine section"

Browse Source
This commit is contained in:
Jenkins
2015-04-03 17:08:39 +00:00
committed by Gerrit Code Review
parent 254d3f9715 f7d81c740d
commit 249db7ecc1
1 changed files with 34 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

35
doc/source/engines.rst
View File

@@ -335,8 +335,8 @@ above stages will be restarted and resuming will occur).
If the engine is suspended while the engine is going through the above If the engine is suspended while the engine is going through the above
stages this will stop any further scheduling stages from occurring and stages this will stop any further scheduling stages from occurring and
all currently executing atoms will be allowed to finish (and their results all currently executing work will be allowed to finish (see
will be saved). :ref:`suspension <suspension>`).
Finishing Finishing
--------- ---------
@@ -353,6 +353,37 @@ failures have occurred then the engine will have finished and if so desired the
:doc:`persistence <persistence>` can be used to cleanup any details that were :doc:`persistence <persistence>` can be used to cleanup any details that were
saved for this execution. saved for this execution.
Special cases
=============
.. _suspension:
Suspension
----------
Each engine implements a :py:func:`~taskflow.engines.base.Engine.suspend`
method that can be used to *externally* (or in the future *internally*) request
that the engine stop :ref:`scheduling <scheduling>` new work. By default what
this performs is a transition of the flow state from ``RUNNING`` into a
``SUSPENDING`` state (which will later transition into a ``SUSPENDED`` state).
Since an engine may be remotely executing atoms (or locally executing them)
and there is currently no preemption what occurs is that the engines
:py:class:`~taskflow.engines.action_engine.runner.Runner` state machine will
detect this transition into ``SUSPENDING`` has occurred and the state
machine will avoid scheduling new work (it will though let active work
continue). After the current work has finished the engine will
transition from ``SUSPENDING`` into ``SUSPENDED`` and return from its
:py:func:`~taskflow.engines.base.Engine.run` method.
.. note::
When :py:func:`~taskflow.engines.base.Engine.run` is returned from at that
point there *may* (but does not have to be, depending on what was active
when :py:func:`~taskflow.engines.base.Engine.suspend` was called) be
unfinished work in the flow that was not finished (but which can be
resumed at a later point in time).
Scoping Scoping
======= =======