openstack/ironic
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Add documentation on parallel argument for driver periodic tasks

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This adds documentation on the parallel argument that may be passed to
the driver_periodic_task decorator, and the potential pitfalls of it
being False.

Change-Id: Ib3e25fda2c90c2f68de5878ae353cf55e05fdb28
Implements: blueprint driver-periodic-tasks
This commit is contained in:
Jim Rollenhagen 2015-02-03 17:10:19 -08:00
parent e4d2622c86
commit 63ee094213
1 changed files with 11 additions and 0 deletions
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11
doc/source/dev/architecture.rst
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@ -93,9 +93,20 @@ driver itself or on any interface with driver_periodic_task_ decorator, e.g.
def task2(self, manager, context):
pass # do something
@base.driver_periodic_task(parallel=False)
def blocking_task(self, manager, context):
pass # do something fast, this blocks other tasks from starting!
Here ``spacing`` argument is a period for a given periodic task.
The ``parallel`` argument may be passed to driver_periodic_task_ and defaults
to True. If False, this task will be run in the periodic task loop, rather
than a separate greenthread. This should be used with caution, as it will
cause all other periodic tasks to be blocked from starting while the
non-parallel task is running. Long running tasks, especially any tasks that
make a remote call (to a BMC, HTTP, etc.) **must** be parallelized.
.. note::
By default periodic task names are derived from method names,
so they should be unique within a Python module.