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