Add diagrams to the architecture doc page
Added some data model diagrams, sequence diagrams and state machine diagrams. The state machine diagrams and sequence diagrams are built with PlantUML whereas data model diagrams are built with Dia. Also added some textual description with the sequence diagrams. Change-Id: Iffbb47b0f2d12ce63eeaa1531a1bd1a790d69e79 Closes-Bug: #1531802
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vmahe
David TARDIVEL
@@ -34,8 +34,8 @@ Components
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AMQP Bus
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--------
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The AMQP message bus handles asynchronous communications between the different
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Watcher components.
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The AMQP message bus handles internal asynchronous communications between the
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different Watcher components.
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.. _cluster_history_db_definition:
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@@ -51,6 +51,14 @@ MongoDB,...) but will probably be more performant when using
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which are optimized for handling time series data, which are arrays of numbers
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indexed by time (a datetime or a datetime range).
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.. _cluster_model_db_definition:
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Cluster Model Database
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------------------------
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This component stores the data related to the
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:ref:`Cluster Data Model <cluster_data_model_definition>`.
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.. _archi_watcher_api_definition:
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Watcher API
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@@ -159,7 +167,7 @@ The :ref:`Strategy <strategy_definition>` is then dynamically loaded (via
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`stevedore <https://github.com/openstack/stevedore/>`_). The
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:ref:`Watcher Decision Engine <watcher_decision_engine_definition>` calls the
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**execute()** method of the :ref:`Strategy <strategy_definition>` class which
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generates a set of :ref:`Actions <action_definition>`.
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generates a solution composed of a set of :ref:`Actions <action_definition>`.
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These :ref:`Actions <action_definition>` are scheduled in time by the
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:ref:`Watcher Planner <watcher_planner_definition>` (i.e., it generates an
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@@ -179,4 +187,187 @@ Audit, the :ref:`Strategy <strategy_definition>` relies on two sets of data:
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So far, only one :ref:`Strategy <strategy_definition>` can be associated to a
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given :ref:`Goal <goal_definition>` via the main Watcher configuration file.
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.. _data_model:
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Data model
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==========
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The following diagram shows the data model of Watcher, especially the
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functional dependency of objects from the actors (Admin, Customer) point of
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view (Goals, Audits, Action Plans, ...):
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.. image:: ./images/functional_data_model.svg
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:width: 100%
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.. _sequence_diagrams:
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Sequence diagrams
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=================
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The following paragraph shows the messages exchanged between the different
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components of Watcher for the most often used scenarios.
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.. _sequence_diagrams_create_audit_template:
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Create a new Audit Template
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---------------------------
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The :ref:`Administrator <administrator_definition>` first creates an
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:ref:`Audit template <audit_template_definition>` providing at least the
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following parameters:
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- A name
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- A goal to achieve
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.. image:: ./images/sequence_create_audit_template.png
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:width: 100%
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The `Watcher API`_ just makes sure that the goal exists (i.e. it is declared
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in the Watcher configuration file) and stores a new audit template in the
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:ref:`Watcher Database <watcher_database_definition>`.
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.. _sequence_diagrams_create_and_launch_audit:
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Create and launch a new Audit
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-----------------------------
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The :ref:`Administrator <administrator_definition>` can then launch a new
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:ref:`Audit <audit_definition>` by providing at least the unique UUID of the
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previously created :ref:`Audit template <audit_template_definition>`:
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.. image:: ./images/sequence_create_and_launch_audit.png
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:width: 100%
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A message is sent on the :ref:`AMQP bus <amqp_bus_definition>` which triggers
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the Audit in the
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:ref:`Watcher Decision Engine <watcher_decision_engine_definition>`:
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.. image:: ./images/sequence_trigger_audit_in_decision_engine.png
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:width: 100%
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The :ref:`Watcher Decision Engine <watcher_decision_engine_definition>` reads
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the Audit parameters from the
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:ref:`Watcher Database <watcher_database_definition>`. It instantiates the
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appropriate :ref:`Strategy <strategy_definition>` (using entry points)
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associated to the :ref:`Goal <goal_definition>` of the
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:ref:`Audit <audit_definition>` (it uses the information of the Watcher
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configuration file to find the mapping between the
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:ref:`Goal <goal_definition>` and the :ref:`Strategy <strategy_definition>`
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python class).
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The :ref:`Watcher Decision Engine <watcher_decision_engine_definition>` also
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builds the :ref:`Cluster Data Model <cluster_data_model_definition>`. This
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data model is needed by the :ref:`Strategy <strategy_definition>` to know the
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current state and topology of the audited
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:ref:`Openstack cluster <cluster_definition>`.
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The :ref:`Watcher Decision Engine <watcher_decision_engine_definition>` calls
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the **execute()** method of the instantiated
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:ref:`Strategy <strategy_definition>` and provides the data model as an input
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parameter. This method computes a :ref:`Solution <strategy_definition>` to
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achieve the goal and returns it to the
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:ref:`Decision Engine <watcher_decision_engine_definition>`. At this point,
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actions are not scheduled yet.
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The :ref:`Watcher Decision Engine <watcher_decision_engine_definition>`
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dynamically loads the :ref:`Watcher Planner <watcher_planner_definition>`
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implementation which is configured in Watcher (via entry points) and calls the
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**schedule()** method of this class with the solution as an input parameter.
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This method finds an appropriate scheduling of
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:ref:`Actions <action_definition>` taking into account some scheduling rules
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(such as priorities between actions).
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It generates a new :ref:`Action Plan <action_plan_definition>` with status
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**RECOMMENDED** and saves it into the
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:ref:`Watcher Database <watcher_database_definition>`. The saved action plan is
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now a scheduled flow of actions.
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If every step executed successfully, the
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:ref:`Watcher Decision Engine <watcher_decision_engine_definition>` updates
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the current status of the Audit to **SUCCEEDED** in the
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:ref:`Watcher Database <watcher_database_definition>` and sends a notification
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on the bus to inform other components that the :ref:`Audit <audit_definition>`
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was successful.
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.. _sequence_diagrams_launch_action_plan:
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Launch Action Plan
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------------------
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The :ref:`Administrator <administrator_definition>` can then launch the
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recommended :ref:`Action Plan <action_plan_definition>`:
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.. image:: ./images/sequence_launch_action_plan.png
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:width: 100%
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A message is sent on the :ref:`AMQP bus <amqp_bus_definition>` which triggers
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the :ref:`Action Plan <action_plan_definition>` in the
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:ref:`Watcher Applier <watcher_applier_definition>`:
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.. image:: ./images/sequence_launch_action_plan_in_applier.png
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:width: 100%
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The :ref:`Watcher Applier <watcher_applier_definition>` will get the
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description of the flow of :ref:`Actions <action_definition>` from the
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:ref:`Watcher Database <watcher_database_definition>` and for each
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:ref:`Action <action_definition>` it will instantiate a corresponding
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:ref:`Action <action_definition>` handler python class.
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The :ref:`Watcher Applier <watcher_applier_definition>` will then call the
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following methods of the :ref:`Action <action_definition>` handler:
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- **validate_parameters()**: this method will make sure that all the
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provided input parameters are valid:
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- If all parameters are valid, the Watcher Applier moves on to the next
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step.
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- If it is not, an error is raised and the action is not executed. A
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notification is sent on the bus informing other components of the
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failure.
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- **preconditions()**: this method will make sure that all conditions are met
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before executing the action (for example, it makes sure that an instance
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still exists before trying to migrate it).
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- **execute()**: this method is what triggers real commands on other
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OpenStack services (such as Nova, ...) in order to change target resource
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state. If the action is successfully executed, a notification message is
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sent on the bus indicating that the new state of the action is
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**SUCCEEDED**.
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If every action of the action flow has been executed successfully, a
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notification is sent on the bus to indicate that the whole
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:ref:`Action Plan <action_plan_definition>` has **SUCCEEDED**.
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.. _state_machine_diagrams:
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State Machine diagrams
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======================
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.. _audit_state_machine:
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Audit State Machine
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-------------------
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The following diagram shows the different possible states of an
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:ref:`Audit <audit_definition>` and what event makes the state change to a new
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value:
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.. image:: ./images/audit_state_machine.png
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:width: 100%
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.. _action_plan_state_machine:
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Action Plan State Machine
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-------------------------
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The following diagram shows the different possible states of an
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:ref:`Action Plan <action_plan_definition>` and what event makes the state
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change to a new value:
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.. image:: ./images/action_plan_state_machine.png
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:width: 100%
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.. _Watcher API: webapi/v1.html
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