Reduce container metrics cardinality

Adds support for passing extra runtime options to cAdvisor.
By default new options disable exporting rarely useful metrics
and labels by cAdvisor. This helps reducing the load on Prometheus
and cAdvisor itself.

Change-Id: I81f3845d6cd03a70a0c8569f8d0ea421027df083

Author: cityofships

ansible/roles/prometheus/defaults/main.yml

@@ -257,3 +257,5 @@ prometheus_openstack_exporter_disabled_dns: "{{ '--disable-service.dns' if not e
 prometheus_openstack_exporter_disabled_object: "{{ '--disable-service.object-store' if not enable_swift | bool else '' }}"
 prometheus_openstack_exporter_disabled_lb: "{{ '--disable-service.load-balancer --disable-metric=neutron-loadbalancers --disable-metric=neutron-loadbalancers_not_active' if not enable_octavia | bool else '' }}"
 prometheus_openstack_exporter_disabled_items: "{{ [prometheus_openstack_exporter_disabled_volume, prometheus_openstack_exporter_disabled_dns, prometheus_openstack_exporter_disabled_object, prometheus_openstack_exporter_disabled_lb|trim]|join(' ')|trim }}"
+
+prometheus_cadvisor_cmdline_extras: "--docker_only --store_container_labels=false --disable_metrics=percpu,referenced_memory,cpu_topology,resctrl,udp,advtcp,sched,hugetlb,memory_numa,tcp,process"

ansible/roles/prometheus/templates/prometheus-cadvisor.json.j2

@@ -1,5 +1,5 @@
 {
-    "command": "/opt/cadvisor --port={{ prometheus_cadvisor_port }} --log_dir=/var/log/kolla/prometheus",
+    "command": "/opt/cadvisor --port={{ prometheus_cadvisor_port }} --log_dir=/var/log/kolla/prometheus {{ prometheus_cadvisor_cmdline_extras }}",
     "config_files": [],
     "permissions": [
         {

etc/kolla/globals.yml

@@ -716,6 +716,10 @@
 # List of extra parameters passed to prometheus. You can add as many to the list.
 #prometheus_cmdline_extras:
 
+# List of extra parameters passed to cAdvisor. By default system cgroups
+# and container labels are not exposed to reduce time series cardinality.
+#prometheus_cadvisor_cmdline_extras: "--docker_only --store_container_labels=false --disable_metrics=percpu,referenced_memory,cpu_topology,resctrl,udp,advtcp,sched,hugetlb,memory_numa,tcp,process"
+
 # Example of setting endpoints for prometheus ceph mgr exporter.
 # You should add all ceph mgr's in your external ceph deployment.
 #prometheus_ceph_mgr_exporter_endpoints:

releasenotes/notes/reduce-cadvisor-cardinality-1213854b9fe0c828.yaml

@@ -0,0 +1,19 @@
+---
+features:
+  - |
+    Adds support for passing extra runtime options to cAdvisor via
+    ``prometheus_cadvisor_cmdline_extras`` new variable. By default
+    system cgroups' metrics are disabled, plus container labels
+    don't get exposed to Prometheus. Expensive metrics that usually
+    should not be exported are also enforced to be disabled - consult
+    `<https://github.com/google/cadvisor/blob/master/docs/runtime_options.md#metrics>`_
+    for a list. These defaults create savings in resources usage by both
+    cAdvisor and Prometheus.
+upgrade:
+  - |
+    cAdvisor has now reduced number of Prometheus metrics and labels
+    exported by default. This means that corresponding timeseries will
+    no longer be created. If existing setup relies on these, eg. for
+    visualisation or alerting, they could be explicitly enabled prior to
+    upgrading with the ``prometheus_cadvisor_cmdline_extras`` new variable.
+    Reference for the possible options: `<https://github.com/google/cadvisor/blob/master/docs/runtime_options.md#metrics>`_.