Add custom-context-for-executions spec
Extend the context with custom parameters to make it generally available for custom actions and support the separation of OpenStack actions from the core. Change-Id: If5ea987f3d9d70c288b12f549434f9e8d6853c66
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Andras Kovi
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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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Custom Context for Executions
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==========================================
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https://blueprints.launchpad.net/mistral/+spec/mistral-custom-context-for-executions
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Currently it is not possible to send contextual parameters to actions. The
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context contains only the OS auth parmeters in the SecurityContext and some
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details about the execution in the ExecutionContext. There is general demand
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to be able to pass parameters at this level to make these pervasively present
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throughout the execution without contaminating the workflow definition.
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Problem description
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===================
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Use Cases
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---------
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1. Pass context parameters to custom actions
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Custom actions may need various contextual parameters, e.g. request/correlation
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IDs, authentication tokens, miscellaneous data. These pieces of data should not
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be passed as parameters to avoid getting logged and to be able to access them
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in any part of the execution.
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2. Provide auth parameters for OpenStack actions
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Currently the OpenStack actions use the SecurityContext to get the authentication
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data. The X-Target-* headers provide an alternative way to override these
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parameters but the size of these headers is limited and already makes them
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unable to handle larger OpenStack installations. [1,2]
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3. Clearly separate the Mistral API authentication parameters from the
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OpenStack Action authentication parameters
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The Mistral API has different plugins for authentication: Keystone and Keycloak
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at the time of writing this specification. OpenStack actions should not rely
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on the parameters used for the Mistral API authentication as this tight
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coupling introduces unwanted restrictions. E.g. it is fairly awkward to
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use Keycloak authentication and run OpenStack actions in the same execution.
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This separation also helps the efforts to separate OpenStack actions from
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the Mistral Core.
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Proposed change
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===============
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Add custom_context dict to the execution type API resources (Execution,
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ActionExecution) and use the data in it to update the context.
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The 'os.auth' key is used to store the X-Target-* headers data in its
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current format. To decrease the size of the final context, this key
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is removed from the custom_context after processing.
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Other keys can be used freely by custom action implmementations. These
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are stored under the 'custom_context' key.
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Alternatives
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------------
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1. Keep using the X-Target-* headers: there are already bugs filed
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2. Send this info hidden in the request body
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E.g. we could add custom_context to the POST request body and we could
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add it to the context in the ContextHook. However, the request body is
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present only in text form in the ContextHook and the parameter cannot
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be left in the request body as it causes the WSME implementation to
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fail unmarshalling the input objects.
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Data model impact
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-----------------
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Not affected.
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REST API impact
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---------------
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Add the custom_context dict field to the Execution and ActionExecution
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API resources.
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Does not involve REST API modification.
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End user impact
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---------------
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mistral exection-create
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~~~~~~~~~~~~~~~~~~~~~~~
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Add the --custom_context parameter.
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mistral execution-create --custom_context='{"correlation_id":"1212ddaa33"}' ...
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mistral run-action
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~~~~~~~~~~~~~~~~~~
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Add the --custom_context parameter.
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mistral run-action --custom_context='{"correlation_id":"1212ddaa33"}' ...
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Performance impact
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------------------
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Large custom_contexts can slow down the execution of workflows as it is
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passed in the RPC messages and saved in the delayed_calls table. For the
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same reason, this can affect the memory usage of components.
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Backward compatibility
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----------------------
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The clients sending the custom_context parameter will not be able to
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use the execution-create and run-action APIs with previous Mistral API
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instances because the resource unmarshalling step will fail.
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Deployer 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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akovi
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Other contributors:
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Work Items
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----------
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Add the --custom_context parameter to the mistral run-action command
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Add the --custom_context parameter to the mistral create-exection command
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Add the custom_context field to the Execution API resource
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Add the custom_context field to the ActionExecution API resource
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Add the support for the special 'os.auth' key (client and API)
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Add the custom_context to mistral-lib
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Testing
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=======
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API test to ensure the correct parameter handling in Execution and ActionExecution
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Check that the custom parameters are loaded in context.custom_context
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References
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==========
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[1] https://bugs.launchpad.net/python-mistralclient/+bug/1702324
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[2] https://bugs.launchpad.net/mistral/+bug/1699248
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