Windows: avoid passing conf objects to subprocesses

On Windows, cotyledon uses multiprocessing instead of forking. Meanwhile,
config objects as well as service manager objects aren't pickleable.

For this reason, we'll avoid passing unpickleable objects to subprocesses,
making all the required initialization on the subprocess side.

This change will allow ceilometer-polling to run on Windows.

Change-Id: Id51db8f06f295bb7019915b53e560df52456cbda
Closes-Bug: #1625602

ceilometer/cmd/polling.py

@@ -14,6 +14,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import os
 import shlex
 
 import cotyledon
@@ -72,18 +73,31 @@ CLI_OPTS = [
 ]
 
 
-def create_polling_service(worker_id, conf):
-    return manager.AgentManager(worker_id,
-                                conf,
-                                conf.polling_namespaces)
-
-
-def main():
+def _prepare_config():
     conf = cfg.ConfigOpts()
     conf.register_cli_opts(CLI_OPTS)
     service.prepare_service(conf=conf)
-    priv_context.init(root_helper=shlex.split(utils._get_root_helper()))
+    return conf
+
+
+def create_polling_service(worker_id, conf=None):
+    if conf is None:
+        conf = _prepare_config()
+        conf.log_opt_values(LOG, log.DEBUG)
+    return manager.AgentManager(worker_id,
+                                conf)
+
+
+def main():
     sm = cotyledon.ServiceManager()
-    sm.add(create_polling_service, args=(conf,))
-    oslo_config_glue.setup(sm, conf)
+    # On Windows, we can only initialize conf objects in the subprocess.
+    # As a consequence, we can't use oslo_config_glue.setup() on Windows,
+    # because cotyledon.ServiceManager objects are not picklable.
+    if os.name == 'nt':
+        sm.add(create_polling_service)
+    else:
+        conf = _prepare_config()
+        priv_context.init(root_helper=shlex.split(utils._get_root_helper()))
+        oslo_config_glue.setup(sm, conf)
+        sm.add(create_polling_service, args=(conf,))
     sm.run()