Add --haproxy-service option.

This option allows the user to dynamically choose which OS services
to use with the HAProxy driver. Ubuntu is the one and only option at
this moment.

libra/worker/drivers/haproxy/driver.py

@@ -19,10 +19,7 @@ from libra.worker.drivers.haproxy.services_base import ServicesBase
 
 class HAProxyDriver(LoadBalancerDriver):
 
-    def __init__(
-        self,
-        ossvc='libra.worker.drivers.haproxy.ubuntu_services.UbuntuServices'
-    ):
+    def __init__(self, ossvc):
         ossvc_driver = import_class(ossvc)
         self.ossvc = ossvc_driver()
         if not isinstance(self.ossvc, ServicesBase):

libra/worker/drivers/haproxy/services_base.py

@@ -13,6 +13,12 @@
 # under the License.
 
 
+# Mapping of --haproxy-services options to a class
+haproxy_services = {
+    'ubuntu': 'libra.worker.drivers.haproxy.ubuntu_services.UbuntuServices'
+}
+
+
 class ServicesBase:
     """
     Operating system services needed by the HAProxy driver.

libra/worker/worker.py

@@ -26,6 +26,7 @@ from libra.common.options import Options, setup_logging
 from libra.common.utils import import_class
 from libra.worker.controller import LBaaSController
 from libra.worker.drivers.base import known_drivers
+from libra.worker.drivers.haproxy.services_base import haproxy_services
 
 
 def lbaas_task(worker, job):
@@ -115,6 +116,11 @@ def main():
         default=[],
         help='add a Gearman job server to the connection list'
     )
+    options.parser.add_argument(
+        '--haproxy-service', dest='haproxy_service',
+        choices=haproxy_services.keys(), default='ubuntu',
+        help='os services to use with HAProxy driver (when used)'
+    )
     args = options.run()
 
     logger = setup_logging('libra_worker', args)
@@ -136,6 +142,10 @@ def main():
 
     logger.info("Selected driver: %s" % args.driver)
     driver_class = import_class(known_drivers[args.driver])
+
+    if args.driver == 'haproxy':
+        driver = driver_class(args.haproxy_service)
+    else:
         driver = driver_class()
 
     logger.info("Job server list: %s" % args.server)