openstack/mistral
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mistral/doc/source/architecture.rst

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Few changes in the doc * Article "Architecture" is too small. It makes sense to add more information. - Added some more information * I think we need to change "How to write an Action Plugin" to just "How to write a custom action". I think the word "plugin" here is not important from user perspective - Done * I think we need to change "How to extend YAQL with a new function" to "How to write a custom YAQL function" and put it right next to "How to write a custom action". That would be more consistent. - Done Change-Id: I9b43694072cb23271e33440741204da3e10b89ac Partial-Implements: blueprint mistral-doc
2016-11-14 14:15:56 +05:30
Mistral Architecture
====================
Mistral is OpenStack workflow service. The main aim of the project is to provide
capability to define, execute and manage tasks and workflows without writing
code.
Basic concepts
~~~~~~~~~~~~~~
A few basic concepts that one has to understand before going through the Mistral
architecture are given below:
* Workflow - consists of tasks (at least one) describing what exact steps should
be made during workflow execution.
* Task - an activity executed within the workflow definition.
* Action - work done when an exact task is triggered.
Mistral components
~~~~~~~~~~~~~~~~~~
Mistral is composed of the following major components:
* API Server
* Engine
* Task Executors
* Scheduler
* Persistence
The following diagram illustrates the architecture of mistral:
Mistral documentation: architecture Implements blueprint: mistral-docs-general Change-Id: I4c398a8677b8c0c6004755db989746f1e918ceea
2015-08-28 17:09:07 +03:00
.. image:: img/mistral_architecture.png
Few changes in the doc * Article "Architecture" is too small. It makes sense to add more information. - Added some more information * I think we need to change "How to write an Action Plugin" to just "How to write a custom action". I think the word "plugin" here is not important from user perspective - Done * I think we need to change "How to extend YAQL with a new function" to "How to write a custom YAQL function" and put it right next to "How to write a custom action". That would be more consistent. - Done Change-Id: I9b43694072cb23271e33440741204da3e10b89ac Partial-Implements: blueprint mistral-doc
2016-11-14 14:15:56 +05:30
API server
----------
The API server exposes REST API to operate and monitor the workflow executions.
Engine
------
Add doc8 rule and check doc/source files doc8 is a linter for documents and used in openstack-manuals. It is better to enforce document linters for simple checking. This change is to add doc8 in tox file and fix line too long in some files. The current rules are as bellow: - invalid rst format - D000 - lines should not be longer than 79 characters - D001 - no trailing whitespace - D002 - no tabulation for indentation - D003 - no carriage returns (use unix newlines) - D004 - no newline at end of file - D005 Change-Id: Ibba3f0e1c3f724563deb27bbf4f13a8040799687 Closes-bug: #1709571
2017-08-09 16:48:14 +08:00
The Engine picks up the workflows from the workflow queue. It handles the
control and dataflow of workflow executions. It also computes which tasks
are ready and places them in a task queue. It passes the data from task to
task, deals with condition transitions, etc.
Few changes in the doc * Article "Architecture" is too small. It makes sense to add more information. - Added some more information * I think we need to change "How to write an Action Plugin" to just "How to write a custom action". I think the word "plugin" here is not important from user perspective - Done * I think we need to change "How to extend YAQL with a new function" to "How to write a custom YAQL function" and put it right next to "How to write a custom action". That would be more consistent. - Done Change-Id: I9b43694072cb23271e33440741204da3e10b89ac Partial-Implements: blueprint mistral-doc
2016-11-14 14:15:56 +05:30
Task Executors
--------------
The Task Executor executes task Actions. It picks up the tasks from the queue,
run actions, and sends results back to the engine.
Scheduler
---------
The scheduler stores and executes delayed calls. It is the important Mistral
component since it interacts with engine and executors. It also triggers
workflows on events (e.g., periodic cron event)
Persistence
-----------
The persistence stores workflow definitions, current execution states, and
past execution results.
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