d511398667
I moved all implemented specs that have been implemented during Ocata cycle in implemented folder. Change-Id: I2abf8fb8d1f3d527934cd647da005ec142e2579e
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3.7 KiB
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146 lines
3.7 KiB
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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=====================
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Make Applier parallel
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=====================
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https://blueprints.launchpad.net/watcher/+spec/parallel-applier
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Problem description
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===================
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Watcher `Applier`_ starts `Action plan`_ with set of `Actions`_, which
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are executed in a sequence. After `planner-storage-action-plan`_ is
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implemented, we have new ``parents`` field that contains list of action's
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uuid child action is connected to. Having ``parents`` field Watcher can build
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Directed Acyclic Graph where each independent Action can be run in parallel
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while actions with some dependencies should fulfill them to be executed.
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Use Cases
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----------
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As an administrator, I would like to be able to run Action plan that will
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launch actions for every node (compute, network, storage) in parallel.
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Proposed change
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===============
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We can launch several concurrent actions in accordance with their parents.
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Workflow engine of Watcher Applier will still use ``watcher_flow`` flow, but
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edges between nodes should be established in accordance with action parents.
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Unlinked actions with no parents should be connected directly to the
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``watcher_flow`` and executed firstly.
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Main class to modify is DefaultWorkFlowEngine, that defines workflow of
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actions executing. Since Watcher Default Planner adds actions to DB
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in accordance with weights (i.e. all migrate actions will be added firstly,
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then resize actions and so on), Applier will get ordered by weight actions
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that can be added to ``watcher_flow`` flow and linked in one ``for loop``.
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In this case algorithm of building directed acyclic graph should have O(n)
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complexity.
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There is estimated pseudocode to show part of default planner's workflow::
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flow = gf.Flow("watcher_flow")
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for a in actions:
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task = TaskFlowActionContainer(a, self)
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flow.add(task)
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if a.parents:
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for parent_id in action.parents:
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parent_action = get_action(actions, parent_id)
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flow.link(parent_action, action, decider=self.decider)
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e = engines.load(flow)
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e.run()
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Alternatives
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------------
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None
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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Since it is perfomance related patch, it is expected to have perfomance
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improvements because of parallel executing of actions instead of sequence.
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In order to reduce the impact on system performance and stability,
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it is better to set the maximum number of concurrent.
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Other deployer impact
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---------------------
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None
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Developer impact
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----------------
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None
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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Alexander Chadin <a.chadin@servionica.ru>
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Work Items
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----------
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* Modify watcher/applier/workflow_engine/default.py to build new parallel
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workflow engine.
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* Update the documentation.
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* Add appropriate unit tests.
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Dependencies
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============
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https://blueprints.launchpad.net/watcher/+spec/planner-storage-action-plan
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Testing
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=======
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* Unit tests will be added to validate these modifications.
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Documentation Impact
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====================
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Update the `Applier`_ documentation in accordance with new changes.
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References
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==========
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.. _Applier: http://docs.openstack.org/developer/watcher/glossary.html#watcher-applier
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.. _Action plan: http://docs.openstack.org/developer/watcher/glossary.html#action-plan
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.. _Actions: http://docs.openstack.org/developer/watcher/glossary.html#action
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.. _planner-storage-action-plan: https://blueprints.launchpad.net/watcher/+spec/planner-storage-action-plan
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History
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=======
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None |