Adding upstream version 14.2.21.upstream/14.2.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/doc/dev/ceph-volume/plugins.rst b/doc/dev/ceph-volume/plugins.rst
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+.. _ceph-volume-plugins:
+
+Plugins
+=======
+``ceph-volume`` started initially to provide support for using ``lvm`` as
+the underlying system for an OSD. It is included as part of the tool but it is
+treated like a plugin.
+
+This modularity, allows for other device or device-like technologies to be able
+to consume and re-use the utilities and workflows provided.
+
+Adding Plugins
+--------------
+As a Python tool, plugins ``setuptools`` entry points. For a new plugin to be
+available, it should have an entry similar to this in its ``setup.py`` file:
+
+.. code-block:: python
+
+    setup(
+        ...
+        entry_points = dict(
+            ceph_volume_handlers = [
+                'my_command = my_package.my_module:MyClass',
+            ],
+        ),
+
+The ``MyClass`` should be a class that accepts ``sys.argv`` as its argument,
+``ceph-volume`` will pass that in at instantiation and call them ``main``
+method.
+
+This is how a plugin for ``ZFS`` could look like for example:
+
+.. code-block:: python
+
+    class ZFS(object):
+
+        help_menu = 'Deploy OSDs with ZFS'
+        _help = """
+    Use ZFS as the underlying technology for OSDs
+
+    --verbose   Increase the verbosity level
+        """
+
+        def __init__(self, argv):
+            self.argv = argv
+
+        def main(self):
+            parser = argparse.ArgumentParser()
+            args = parser.parse_args(self.argv)
+            ...
+
+And its entry point (via ``setuptools``) in ``setup.py`` would looke like:
+
+.. code-block:: python
+
+        entry_points = {
+            'ceph_volume_handlers': [
+                'zfs = ceph_volume_zfs.zfs:ZFS',
+            ],
+        },
+
+After installation, the ``zfs`` subcommand would be listed and could be used
+as::
+
+    ceph-volume zfs