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Documentation on goal and efficacy

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In this changeset, I wrote a documentation detailing how one can
implement a new goal plugin. I also mention to define the efficacy
specification for a given goal.

Partially Implements: blueprint efficacy-indicator

Change-Id: Iba267ae312f248b49d4600504f11678cdc225622
This commit is contained in:
Vincent Françoise
2016-05-20 14:28:08 +02:00
parent 442512cd71
commit 45801cf9c5
24 changed files with 1384 additions and 541 deletions
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149
doc/source/dev/plugin/strategy-plugin.rst
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@@ -28,8 +28,8 @@ configured so that it would provide you all the metrics you need to be able to
use your strategy.
Create a new plugin
===================
Create a new strategy plugin
============================
In order to create a new strategy, you have to:
@@ -53,6 +53,8 @@ Here is an example showing how you can write a plugin called ``NewStrategy``:
.. code-block:: python
# filepath: thirdparty/new.py
# import path: thirdparty.new
import abc
import six
@@ -88,9 +90,12 @@ Here is an example showing how you can write a plugin called ``NewStrategy``:
As you can see in the above example, the :py:meth:`~.BaseStrategy.execute`
method returns a :py:class:`~.BaseSolution` instance as required. This solution
is what wraps the abstract set of actions the strategy recommends to you. This
solution is then processed by a :ref:`planner <planner_definition>` to produce
an action plan which contains the sequenced flow of actions to be
executed by the :ref:`Watcher Applier <watcher_applier_definition>`.
solution is then processed by a :ref:`planner <watcher_planner_definition>` to
produce an action plan which contains the sequenced flow of actions to be
executed by the :ref:`Watcher Applier <watcher_applier_definition>`. This
solution also contains the various :ref:`efficacy indicators
<efficacy_indicator_definition>` alongside its computed :ref:`global efficacy
<efficacy_definition>`.
Please note that your strategy class will expect to find the same constructor
signature as BaseStrategy to instantiate you strategy. Therefore, you should
@@ -98,7 +103,7 @@ ensure that your ``__init__`` signature is identical to the
:py:class:`~.BaseStrategy` one.
Create a new goal
Strategy efficacy
=================
As stated before, the ``NewStrategy`` class extends a class called
@@ -106,126 +111,12 @@ As stated before, the ``NewStrategy`` class extends a class called
abstract methods which are defined within the :py:class:`~.BaseStrategy` parent
class.
Once you are confident in your strategy plugin, the next step is now to
classify your goal by assigning it a proper goal. To do so, you can either
reuse existing goals defined in Watcher. As of now, four goal-oriented abstract
classes are defined in Watcher:
- :py:class:`~.UnclassifiedStrategy` which is the one I mentioned up until now.
- :py:class:`~.DummyBaseStrategy` which is used by :py:class:`~.DummyStrategy`
for testing purposes.
- :py:class:`~.ServerConsolidationBaseStrategy`
- :py:class:`~.ThermalOptimizationBaseStrategy`
If none of the above actually correspond to the goal your new strategy
achieves, you can define a brand new one. To do so, you need to:
- Extend the :py:class:`~.BaseStrategy` class to make your new goal-oriented
strategy abstract class :
- Implement its :py:meth:`~.BaseStrategy.get_goal_name` class method to
return the **unique** ID of the goal you want to achieve.
- Implement its :py:meth:`~.BaseStrategy.get_goal_display_name` class method
to return the translated display name of the goal you want to achieve.
Note: Do not use a variable to return the translated string so it can be
automatically collected by the translation tool.
- Implement its :py:meth:`~.BaseStrategy.get_translatable_goal_display_name`
class method to return the goal translation key (actually the english
display name). The value return should be the same as the string translated
in :py:meth:`~.BaseStrategy.get_goal_display_name`.
Here is an example showing how you can define a new ``NEW_GOAL`` goal and
modify your ``NewStrategy`` plugin so it now achieves the latter:
.. code-block:: python
import abc
import six
from watcher._i18n import _
from watcher.decision_engine.strategy.strategies import base
@six.add_metaclass(abc.ABCMeta)
class NewGoalBaseStrategy(base.BaseStrategy):
@classmethod
def get_goal_name(cls):
return "NEW_GOAL"
@classmethod
def get_goal_display_name(cls):
return _("New goal")
@classmethod
def get_translatable_goal_display_name(cls):
return "New goal"
class NewStrategy(NewGoalBaseStrategy):
def __init__(self, config, osc=None):
super(NewStrategy, self).__init__(config, osc)
def execute(self, original_model):
self.solution.add_action(action_type="nop",
input_parameters=parameters)
# Do some more stuff here ...
return self.solution
@classmethod
def get_name(cls):
return "new_strategy"
@classmethod
def get_display_name(cls):
return _("New strategy")
@classmethod
def get_translatable_display_name(cls):
return "New strategy"
Define configuration parameters
===============================
At this point, you have a fully functional strategy. However, in more complex
implementation, you may want to define some configuration options so one can
tune the strategy to its needs. To do so, you can implement the
:py:meth:`~.Loadable.get_config_opts` class method as followed:
.. code-block:: python
from oslo_config import cfg
class NewStrategy(NewGoalBaseStrategy):
# [...]
def execute(self, original_model):
assert self.config.test_opt == 0
# [...]
def get_config_opts(self):
return [
cfg.StrOpt('test_opt', help="Demo Option.", default=0),
# Some more options ...
]
The configuration options defined within this class method will be included
within the global ``watcher.conf`` configuration file under a section named by
convention: ``{namespace}.{plugin_name}``. In our case, the ``watcher.conf``
configuration would have to be modified as followed:
.. code-block:: ini
[watcher_strategies.new_strategy]
# Option used for testing.
test_opt = test_value
Then, the configuration options you define within this method will then be
injected in each instantiated object via the ``config`` parameter of the
:py:meth:`~.BaseStrategy.__init__` method.
One thing this :py:class:`~.UnclassifiedStrategy` class defines is that our
``NewStrategy`` achieves the ``unclassified`` goal. This goal is a peculiar one
as it does not contain any indicator nor does it calculate a global efficacy.
This proves itself to be quite useful during the development of a new strategy
for which the goal has yet to be defined or in case a :ref:`new goal
<implement_goal_plugin>` has yet to be implemented.
Abstract Plugin Class
@@ -249,16 +140,16 @@ strategy must be registered as a named entry point under the
pbr_, this entry point should be placed in your ``setup.cfg`` file.
The name you give to your entry point has to be unique and should be the same
as the value returned by the :py:meth:`~.BaseStrategy.get_id` class method of
as the value returned by the :py:meth:`~.BaseStrategy.get_name` class method of
your strategy.
Here below is how you would proceed to register ``DummyStrategy`` using pbr_:
Here below is how you would proceed to register ``NewStrategy`` using pbr_:
.. code-block:: ini
[entry_points]
watcher_strategies =
dummy_strategy = thirdparty.dummy:DummyStrategy
new_strategy = thirdparty.new:NewStrategy
To get a better understanding on how to implement a more advanced strategy,