Use Cotyledon oslo config glue

Oslo.service was providing some oslo config configuration.
mainly to print all cfg options on startup and a timeout
option in case of service doesn't stop gracefully in an timely fashion.

It also reload the configuration file on sighup.

This change uses the optional cotyledon helper to do that stuffs.

Change-Id: I6227fab55b2f4d33611ca3c4bcf01239ff585748

etc/gnocchi/gnocchi-config-generator.conf

@@ -6,4 +6,5 @@ namespace = oslo.db
 namespace = oslo.log
 namespace = oslo.middleware
 namespace = oslo.policy
+namespace = cotyledon
 namespace = keystonemiddleware.auth_token

gnocchi/cli.py

@@ -19,6 +19,7 @@ import time
 import uuid
 
 import cotyledon
+from cotyledon import oslo_config_glue
 from futurist import periodics
 import msgpack
 from oslo_config import cfg
@@ -286,15 +287,29 @@ class MetricProcessor(MetricProcessBase):
 class MetricdServiceManager(cotyledon.ServiceManager):
     def __init__(self, conf):
         super(MetricdServiceManager, self).__init__()
+        oslo_config_glue.setup(self, conf)
+
         self.conf = conf
         self.queue = multiprocessing.Manager().Queue()
 
         self.add(MetricScheduler, args=(self.conf, self.queue))
-        self.add(MetricProcessor, args=(self.conf, self.queue),
-                 workers=conf.metricd.workers)
+        self.metric_processor_id = self.add(
+            MetricProcessor, args=(self.conf, self.queue),
+            workers=conf.metricd.workers)
         self.add(MetricReporting, args=(self.conf,))
         self.add(MetricJanitor, args=(self.conf,))
 
+        self.register_hooks(on_reload=self.on_reload)
+
+    def on_reload(self):
+        # NOTE(sileht): We do not implement reload() in Workers so all workers
+        # will received SIGHUP and exit gracefully, then their will be
+        # restarted with the new number of workers. This is important because
+        # we use the number of worker to declare the capability in tooz and
+        # to select the block of metrics to proceed.
+        self.reconfigure(self.metric_processor_id,
+                         workers=self.conf.metricd.workers)
+
     def run(self):
         super(MetricdServiceManager, self).run()
         self.queue.close()

releasenotes/notes/reloading-734a639a667c93ee.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - gnocchi-metricd now uses the cotyledon/oslo.config helper to handle
+    configuration file reloading. You can dynamically change the number
+    of workers by changing the configuration file and sending SIGHUP to the
+    metricd master process.

requirements.txt

@@ -12,7 +12,7 @@ pecan>=0.9
 pytimeparse>=1.1.5
 futures
 jsonpatch
-cotyledon>=1.2.2
+cotyledon>=1.5.0
 requests
 six
 stevedore