Datasource base.py owns available metrics for datasources

[Dantali0n]

/watcher/datasource/base.py owns the variable METRIC_MAP which contains a dictionary with all the available metrics for Ceilometer, Gnocchi and Monasca.

The proposed solution is to have an abstract map for the base class so that datasources that implement this class are made aware of the metrics they can provide to help watcher make decisions.

The code written in /watcher/datasource/manager.py get_backend can then be rewritten to read from individual datasource classes instead of from base.py

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/636761

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/636761
Committed: https://git.openstack.org/cgit/openstack/watcher/commit/?id=73830387c65037cd1de8404f52dda1a307e71ebd
Submitter: Zuul
Branch: master

commit 73830387c65037cd1de8404f52dda1a307e71ebd
Author: Dantali0n <email address hidden>
Date: Wed Feb 13 22:24:01 2019 +0100

    Move datasources metric mappings out of base.py

    Moved the metric mappings for Ceilormeter, Gnocchi & Monasca out of
    base.py. The datasources manager now uses classes extending base.py
    their NAME attribute as key in the dictionary of total available
    mappings and datasources. base.py still contains a template
    definition of all available mappings so that anyone extending the
    base class can identify all the possible endpoints they can map to.

    Change-Id: I6a826423031b5a6a60c4cd5fe24f74b8400f6b55
    Closes-Bug: #1815769

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/watcher 2.0.0.0rc1 release candidate.