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===============
Scope fetcher
===============
The fetcher retrieves a list of scopes to rate. These scopes are then passed to
the collector, in combination with each metric type.
Implementation
==============
Fetchers are extremely simple. A custom fetcher must implement the following
class:
.. autoclass:: cloudkitty.fetcher.BaseFetcher
:members: get_tenants
The ``get_tenants`` method takes no parameters and returns a list of unique
scope_ids, represented as ``str``.
The name of the new fetcher must be specified as a class attribute.
Options for the new fetcher must be registered under the ``fetcher_<name>``
config section.
A new scope fetcher must be implemented in a new module, in
``cloudkitty.fetcher.<name>.py``. Its class must be called ``<Name>Fetcher``.
An entrypoint must be registered for new fetchers. This is done in the
``setup.cfg`` file, located at the root of the repository:
.. code-block:: ini
cloudkitty.fetchers =
keystone = cloudkitty.fetcher.keystone:KeystoneFetcher
source = cloudkitty.fetcher.source:SourceFetcher
# [...]
custom = cloudkitty.fetcher.custom:CustomFetcher
Example
=======
The most simple scope fetcher is the ``SourceFetcher``. It simply returns a
list of scopes read from the configuration file:
.. code-block:: python
# In cloudkitty/fetcher/source.py
from oslo_config import cfg
from cloudkitty import fetcher
FETCHER_SOURCE_OPTS = 'fetcher_source'
fetcher_source_opts = [
cfg.ListOpt(
'sources',
default=list(),
help='list of source identifiers',
),
]
# Registering the 'sources' option in the 'fetcher_source' option
cfg.CONF.register_opts(fetcher_source_opts, FETCHER_SOURCE_OPTS)
CONF = cfg.CONF
class SourceFetcher(fetcher.BaseFetcher):
# Defining the name of the fetcher
name = 'source'
# Returning the list of scopes read from the configuration file
def get_tenants(self):
return CONF.fetcher_source.sources
More complex examples can be found in the ``cloudkitty/fetcher`` directory.
|
