Using ServiceLauncher instead of ProcessLauncher

This patch added implementation that instancemonitor starts
by using ServiceLauncher instead of ProcessLauncher.

Change-Id: I0eb7be7989b8af1b901105b433e7b782f7312e9f

masakarimonitors/cmd/instancemonitor.py

@@ -32,8 +32,6 @@ def main():
     logging.setup(CONF, "masakarimonitors")
     utils.monkey_patch()
 
-    launcher = service.process_launcher()
     server = service.Service.create(binary='masakarimonitors-instancemonitor')
-    launcher.launch_service(server)
-
-    launcher.wait()
+    service.serve(server)
+    service.wait()

masakarimonitors/service.py

@@ -118,5 +118,19 @@ class Service(service.Service):
         self.manager.reset()
 
 
-def process_launcher():
-    return service.ProcessLauncher(CONF)
+# NOTE: the global launcher is to maintain the existing
+#       functionality of calling service.serve +
+#       service.wait
+_launcher = None
+
+
+def serve(server, workers=None):
+    global _launcher
+    if _launcher:
+        raise RuntimeError(_('serve() can only be called once'))
+
+    _launcher = service.launch(CONF, server, workers=workers)
+
+
+def wait():
+    _launcher.wait()