Use event-driven task distribution.

Use Green Threads via the eventlet module to execute the server
tasks. So far, the only task is the Gearman worker. This is another
step forward to being able to execute a Gearman client task.

Change-Id: I4824753d3a3a07ad8ccf521a957efd41150b0752

libra/worker/main.py

@@ -12,6 +12,9 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import eventlet
+eventlet.monkey_patch()
+
 import daemon
 import daemon.pidfile
 import grp
@@ -24,24 +27,32 @@ from libra.worker.drivers.base import known_drivers
 from libra.worker.drivers.haproxy.services_base import haproxy_services
 
 
-class Server(object):
+class EventServer(object):
     """
     Encapsulates server activity so we can run it in either daemon or
     non-daemon mode.
     """
 
-    def __init__(self, logger, servers, reconnect_sleep):
+    def __init__(self, logger):
         self.logger = logger
-        self.driver = None
-        self.servers = servers
-        self.reconnect_sleep = reconnect_sleep
 
-    def main(self):
+    def main(self, tasks):
-        """ Main method of the server.  """
+        """
-        config_manager(self.logger,
+        Main method of the server.
-                       self.driver,
+
-                       self.servers,
+        tasks
-                       self.reconnect_sleep)
+            A tuple with two items: a function name, and a tuple with
+            that function's arguments.
+        """
+
+        thread_list = []
+
+        for task, args in tasks:
+            thread_list.append(eventlet.spawn(task, *args))
+
+        for thd in thread_list:
+            thd.wait()
+
         self.logger.info("Shutting down")
 
 
@@ -98,11 +109,15 @@ def main():
         driver = driver_class()
 
     logger.info("Job server list: %s" % args.server)
-    server = Server(logger, args.server, args.reconnect_sleep)
+    server = EventServer(logger)
-    server.driver = driver
+
+    # Tasks to execute in parallel
+    task_list = [
+        (config_manager, (logger, driver, args.server, args.reconnect_sleep))
+    ]
 
     if args.nodaemon:
-        server.main()
+        server.main(task_list)
     else:
         context = daemon.DaemonContext(
             working_directory='/etc/haproxy',
@@ -124,6 +139,6 @@ def main():
                 return 1
 
         with context:
-            server.main()
+            server.main(task_list)
 
     return 0

tools/pip-requires

@@ -1,3 +1,4 @@
+eventlet
 gearman
 python-daemon
 requests