Mistral Actions Library
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Dougal Matthews
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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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Mistral Actions Library
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=======================
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Launchpad blueprint:
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https://blueprints.launchpad.net/mistral/+spec/mistral-actions-api-separate-openstack-actions
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This specification outlines a proposal to move the OpenStack actions to
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mistral-extra and define a process for accepting other third party actions
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in mistral-extra.
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Problem description
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===================
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Mistral ships with a set of standard generic actions and a set of actions
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specific to OpenStack. The OpenStack actions help improve the utility of
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Mistral but including them in Mistral itself raises a number of limitations.
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- Some users won't want OpenStack actions. (i.e. Mistral running outside
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OpenStack).
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- Some users will only want specific OpenStack actions. (i.e. their deployment
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only includes certain OpenStack projects).
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- OpenStack actions can easily become out of date as the OpenStack clients can
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evolve quickly. Releases to these actions require full Mistral releases.
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The OpenStack actions make Mistral much more useful in OpenStack environments
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but there isn't a clear place to collect or develop other Mistral actions.
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Without a wider set of actions that integrate with other services and projects
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Mistral is unlikely to become used more widely.
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Use Cases
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---------
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- As an administrator and deployer I want control over the actions included
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with Mistral.
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- As a developer I want a clear place to contribute to actions and add
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support for third party actions.
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- As an end user I want my workflows to have access to a library of actions
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that allow my workflows to do more without having to create custom actions.
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Proposed change
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===============
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This specification proposes moving the current OpenStack actions to the
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mistral-extra repo, which can be then referred to as the Mistral actions
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library. This repository will depend on mistral-lib, as being developed under
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the `custom actions API spec <mistral-custom-actions-api.html>`_.
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mistral-extra will contain a Python namespace for all the OpenStack actions,
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this will likely be ``mistral_extra.openstack``. The action names will remain
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as they are now to maintain backwards compatability. It will also allow other
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actions to be added to this project if they meet the requirements.
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For an action to be considered for mistral-extra it should be generic and
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useful for a wide range of users and not specific to one user or project. There
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should also be a way to automate the testing of this action to verify that it
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continues to work over time. Without the ability to do an integration test the
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actions will become impossible to maintain as the library grows. Generally
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useful actions are also candidates to be included in Mistral itself with the
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other ``std.*`` actions.
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A configuration file will be added that allows users to specify which actions
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they want to include. By default this config will match the existing behaviour
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and include all OpenStack actions, but other actions will need to be enabled
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for each project.
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Alternatives
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------------
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Alternatively we could continue storing the actions in Mistral and third party
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actions could be developed outside of Mistral entirely. This may work, but it
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would make it much harder to grow a cohesive library that is easy to use.
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Data model impact
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-----------------
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No data model changes are required.
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REST API impact
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---------------
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No API changes are required.
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Python API
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----------
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The mistral-extra repository will also provide a stable Python API that can be
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used by action developers as a library. This will allow them to access the
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OpenStack actions and extend or customise them. The API is still to be
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determined but usage will likely look something like this.
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::
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from mistral_extra import openstack
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class CustomNovaAction(openstack.NovaAction):
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def run(self, context):
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nova_client = self.get_client(context)
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# do something custom and return
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Access to the Python clients for OpenStack projects will also be possible. This
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will allow custom action developers to easily consume multiple OpenStack
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clients.
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::
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from mistral_extra import openstack
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from mistral_lib import actions
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class CustomAction(actions.Action):
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def run(self, context):
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nova_client = openstack.NovaAction.get_client(context)
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glance_client = openstack.GlanceAction.get_client(context)
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End user impact
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---------------
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Users will primarily interact with the feature by customising the mistral-extra
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config file. This will need to be documented.
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Performance Impact
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------------------
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No performance impact.
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Deployer impact
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---------------
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No additional steps will be required by default for deployers. However, they
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will have greater control of their deployment and which actions are included
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and available to users.
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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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d0ugal
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Other contributors:
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None
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Work Items
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----------
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- Copy OpenStack actions to mistral-extra
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- Package and release mistral-extra and update Mistral to depend on it
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- Remove OpenStack actions from mistral
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- Update the documentation to reflect the configuration of mistral-lib
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Dependencies
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============
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* `Custom Actions API <mistral-custom-actions-api.html>`_
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Testing
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=======
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This will reduce the testing burden on the main Mistral repository. However,
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additional test cases will be needed for mistral-extra. It may also be wise to
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setup a periodic test to verify that a recent version of Mistral master still
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works with mistral-extra.
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References
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==========
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None
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