Add subsystem metrics

- Adds a Metrics() class that can track data such as number of
events the callback receiver inserted into database
- Exposes this metric data at the api/v2/metrics/ endpoint.
This data is prometheus-friendly
- Metric data is stored in memory, then periodically saved to Redis.
- Metric data is periodically broadcast to other nodes in the cluster,
so that each node has a copy of the most recent metric data collected.

awx/api/views/metrics.py

@@ -14,6 +14,7 @@ from rest_framework.exceptions import PermissionDenied
 
 # AWX
 # from awx.main.analytics import collectors
+import awx.main.analytics.subsystem_metrics as s_metrics
 from awx.main.analytics.metrics import metrics
 from awx.api import renderers
 
@@ -33,5 +34,10 @@ class MetricsView(APIView):
     def get(self, request):
         ''' Show Metrics Details '''
         if request.user.is_superuser or request.user.is_system_auditor:
-            return Response(metrics().decode('UTF-8'))
+            metrics_to_show = ''
+            if not request.query_params.get('subsystemonly', "0") == "1":
+                metrics_to_show += metrics().decode('UTF-8')
+            if not request.query_params.get('dbonly', "0") == "1":
+                metrics_to_show += s_metrics.metrics(request)
+            return Response(metrics_to_show)
         raise PermissionDenied()