List available drivers in current Cinder package

This patch adds a list_supported_drivers method that will return a
dictionary indexed by the driver name with the path of the driver, the
name of the class, the version of the driver, and some additional
information.

HISTORY.rst

@@ -2,6 +2,14 @@
 History
 =======
 
+0.3.3 (2019-01-xx)
+------------------
+
+- Features:
+
+  - List drivers available in current Cinder installation.
+
+
 0.3.2 (2019-01-22)
 ------------------
 

cinderlib/__init__.py

@@ -38,3 +38,4 @@ setup = cinderlib.setup
 Backend = cinderlib.Backend
 
 get_connector_properties = objects.brick_connector.get_connector_properties
+list_supported_drivers = cinderlib.Backend.list_supported_drivers

cinderlib/cinderlib.py

@@ -16,6 +16,7 @@
 from __future__ import absolute_import
 import json as json_lib
 import logging
+import multiprocessing
 import os
 import six
 
@@ -27,6 +28,7 @@ from cinder import objects as cinder_objects
 # VA_LIST = objects.VolumeAttachmentList
 cinder_objects.register_all()  # noqa
 
+from cinder.interface import util as cinder_interface_util
 from cinder import utils
 from cinder.volume import configuration
 from cinder.volume import manager
@@ -351,6 +353,32 @@ class Backend(object):
             self._volumes = None
             self.volumes
 
+    @staticmethod
+    def list_supported_drivers():
+        """Returns dictionary with driver classes names as keys."""
+        def list_drivers(queue):
+            cwd = os.getcwd()
+            # Go to the parent directory directory where Cinder is installed
+            os.chdir(utils.__file__.rsplit(os.sep, 2)[0])
+            try:
+                drivers = cinder_interface_util.get_volume_drivers()
+                mapping = {d.class_name: vars(d) for d in drivers}
+                # Drivers contain class instances which are not serializable
+                for driver in mapping.values():
+                    driver.pop('cls', None)
+            finally:
+                os.chdir(cwd)
+            queue.put(mapping)
+
+        # Use a different process to avoid having all driver classes loaded in
+        # memory during our execution.
+        queue = multiprocessing.Queue()
+        p = multiprocessing.Process(target=list_drivers, args=(queue,))
+        p.start()
+        p.join()
+        result = queue.get()
+        return result
+
 
 setup = Backend.global_setup
 # Used by serialization.load