Use stevedore to load API handler

Updates controller base to load handler via stevedore
Updates setup.cfg with entry point
Updates octavia.conf for api_handler default example
Updates config.py for api_handler
Updates requirements.txt for stevedore

Change-Id: I67e3da376fad1d48cec7f56f990c4b13ac7f4b83

etc/octavia.conf

@@ -5,6 +5,7 @@
 # debug = False
 # bind_host = 0.0.0.0
 # bind_port = 9876
+# api_handler = simulated_handler
 
 [database]
 # This line MUST be changed to actually run the plugin.

octavia/api/v1/controllers/base.py

@@ -12,19 +12,26 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from oslo.config import cfg
 from pecan import rest
+from stevedore import driver as stevedore_driver
 
-from octavia.api.v1.handlers.controller_simulator import handler
 from octavia.api.v1.types import load_balancer as lb_types
 from octavia.api.v1.types import pool as pool_types
 from octavia.db import repositories
 
+CONF = cfg.CONF
+
 
 class BaseController(rest.RestController):
 
     def __init__(self):
-        self.handler = handler.SimulatedControllerHandler()
         self.repositories = repositories.Repositories()
+        self.handler = stevedore_driver.DriverManager(
+            namespace='octavia.api.handlers',
+            name=CONF.api_handler,
+            invoke_on_load=True
+        ).driver
 
     def _convert_db_to_type(self, db_entity, to_type):
         """Converts a data model into a Octavia WSME type

octavia/common/config.py

@@ -34,6 +34,8 @@ core_opts = [
                help=_("The host IP to bind to")),
     cfg.IntOpt('bind_port', default=9876,
                help=_("The port to bind to")),
+    cfg.StrOpt('api_handler', default='simulated_handler',
+               help=_("The handler that the API communicates with")),
     cfg.StrOpt('api_paste_config', default="api-paste.ini",
                help=_("The API paste config file to use")),
     cfg.StrOpt('api_extensions_path', default="",

requirements.txt

@@ -15,6 +15,7 @@ netaddr>=0.7.12
 python-neutronclient>=2.3.11,<3
 WebOb>=1.2.3
 six>=1.9.0
+stevedore>=1.3.0,<1.4.0  # Apache-2.0
 oslo.config>=1.9.3,<1.10.0  # Apache-2.0
 oslo.context>=0.2.0,<0.3.0                     # Apache-2.0
 oslo.db>=1.7.0,<1.8.0  # Apache-2.0

setup.cfg

@@ -28,3 +28,8 @@ warnerrors = True
 
 [wheel]
 universal = 1
+
+[entry_points]
+octavia.api.handlers =
+    simulated_handler = octavia.api.v1.handlers.controller_simulator.handler:SimulatedControllerHandler
+    queue_producer = octavia.api.v1.handlers.queue.producer:ProducerHandler