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Add reference to Ceilometer developer guide 

Strategies can require, from Watcher, metrics collected on the IAAS.
Watcher uses only Ceilometer API to retrieve metrics.
Change the metrics database backend, add a new metric is not in
the scope of Watcher, but rather in the Ceilometer one. We add some
links to Ceilometer documentation about these topics.

Change-Id: If37c7df8e5852f5ecf94b4a9eb9c8c91fe6637eb
This commit is contained in:
David TARDIVEL 2016-01-19 15:01:40 +01:00
parent 63d9500904
commit 894dfa0d7e
1 changed files with 20 additions and 6 deletions
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26
doc/source/dev/strategy-plugin.rst
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@ -128,13 +128,27 @@ check/configure the latter so your new strategy can be fully functional.
Querying metrics
----------------
The metrics available depend on the hypervisors that OpenStack manages on
the specific implementation. You can find the metrics available per hypervisor
and OpenStack release on the OpenStack site.
A large set of metrics, generated by OpenStack modules, can be used in your
strategy implementation. To collect these metrics, Watcher provides a
`Helper`_ to the Ceilometer API, which makes this API reusable and easier
to used.
There are different possible ways to obtain usage metrics in Watcher, you can
use the default Ceilometer API or our Helper.
The Helper attempted to make the Ceilometer API more reusable and easy to use.
If you want to use your own metrics database backend, please refer to the
`Ceilometer developer guide`_. Indeed, Ceilometer's pluggable model allows
for various types of backends. A list of the available backends is located
here_. The Ceilosca project is a good example of how to create your own
pluggable backend.
Finally, if your strategy requires new metrics not covered by Ceilometer, you
can add them through a Ceilometer `plugin`_.
.. _`Helper`: https://github.com/openstack/watcher/blob/master/watcher/metrics_engine/cluster_history/ceilometer.py#L31
.. _`Ceilometer developer guide`: http://docs.openstack.org/developer/ceilometer/architecture.html#storing-the-data
.. _`here`: http://docs.openstack.org/developer/ceilometer/install/dbreco.html#choosing-a-database-backend
.. _`plugin`: http://docs.openstack.org/developer/ceilometer/plugins.html
.. _`Ceilosca`: https://github.com/openstack/monasca-ceilometer/blob/master/ceilosca/ceilometer/storage/impl_monasca.py
Read usage metrics using the Python binding
-------------------------------------------