Add a worker for reporting global stats to Prometheus

Fixes #1789

util/metrics/metricqueue.py

@@ -57,6 +57,11 @@ class MetricQueue(object):
                                                           labelnames=['namespace', 'repo_name',
                                                                       'status'])
 
+    self.repository_count = prom.create_gauge('repository_count', 'Number of repositories')
+    self.user_count = prom.create_gauge('user_count', 'Number of users')
+    self.org_count = prom.create_gauge('org_count', 'Number of Organizations')
+    self.robot_count = prom.create_gauge('robot_count', 'Number of robot accounts')
+
     # Deprecated: Define an in-memory queue for reporting metrics to CloudWatch or another
     # provider.
     self._queue = None