metricd: remove janitor process

This merge the janitor process in the worker 0 of the metric processor. This
saves some megabytes of memory.

Closes #652

gnocchi/cli/metricd.py

@@ -148,6 +148,9 @@ def __init__(self, worker_id, conf):
         self._get_sacks_to_process = cachetools.func.ttl_cache(
             ttl=conf.metricd.metric_processing_delay
         )(self._get_sacks_to_process)
+        if worker_id == 0:
+            self.name = "processing+janitor"
+            self._last_expunge = utils.StopWatch().start()
 
     @tenacity.retry(
         wait=utils.wait_exponential,
@@ -217,6 +220,12 @@ def _get_sacks_to_process(self):
             return self._tasks or self.fallback_tasks
 
     def _run_job(self):
+        if (self.worker_id == 0 and
+           self._last_expunge.elapsed()
+           >= self.conf.metric.metric_cleanup_delay):
+            self.store.expunge_metrics(self.incoming, self.index)
+            self._last_expunge.reset()
+
         m_count = 0
         s_count = 0
         # We are going to process the sacks we got notified for, and if we got
@@ -258,18 +267,6 @@ def close_services(self):
         self.coord.stop()
 
 
-class MetricJanitor(MetricProcessBase):
-    name = "janitor"
-
-    def __init__(self,  worker_id, conf):
-        super(MetricJanitor, self).__init__(
-            worker_id, conf, conf.metricd.metric_cleanup_delay)
-
-    def _run_job(self):
-        self.store.expunge_metrics(self.incoming, self.index)
-        LOG.debug("Metrics marked for deletion removed from backend")
-
-
 class MetricdServiceManager(cotyledon.ServiceManager):
     def __init__(self, conf):
         super(MetricdServiceManager, self).__init__()
@@ -281,7 +278,6 @@ def __init__(self, conf):
             workers=conf.metricd.workers)
         if self.conf.metricd.metric_reporting_delay >= 0:
             self.add(MetricReporting, args=(self.conf,))
-        self.add(MetricJanitor, args=(self.conf,))
 
         self.register_hooks(on_reload=self.on_reload)
 

gnocchi/opts.py

@@ -153,7 +153,7 @@ def list_opts():
                        deprecated_group='storage',
                        default=300,
                        required=True,
-                       help="How many seconds to wait between "
+                       help="How many seconds to wait (at least) between "
                        "cleaning of expired data"),
             cfg.IntOpt('processing_replicas',
                        default=3,