prometheus-adapter: add prefix option to config for container metrics (#1844)

This commit adds the options `containerMetricsPrefix`
to the prometheus-adapter config-map generator. By default this option
is the empty string and doesn't change the current behavior. If set
however to e.g. `pa_`, the prometheus-adapter configuration will add
this prefix to all container_ queries in the resource rules.
This enables users of kube-prometheus to define a specialised service
monitor, that only expose the prometheus-adapter related container metrics with a
different configuration, like `honorTimestamps: true` or a tighter
scrape interval.

Signed-off-by: Jan Fajerski <jfajersk@redhat.com>

jsonnet/kube-prometheus/components/prometheus-adapter.libsonnet

@@ -31,6 +31,7 @@ local defaults = {
     nodeExporter: '4m',
     windowsExporter: '4m',
   },
+  containerMetricsPrefix:: '',
 
   prometheusURL:: error 'must provide prometheusURL',
   config:: {
@@ -39,10 +40,10 @@ local defaults = {
         containerQuery: |||
           sum by (<<.GroupBy>>) (
             irate (
-                container_cpu_usage_seconds_total{<<.LabelMatchers>>,container!="",pod!=""}[%(kubelet)s]
+                %(containerMetricsPrefix)scontainer_cpu_usage_seconds_total{<<.LabelMatchers>>,container!="",pod!=""}[%(kubelet)s]
             )
           )
-        ||| % $.rangeIntervals,
+        ||| % { kubelet: $.rangeIntervals.kubelet, containerMetricsPrefix: $.containerMetricsPrefix },
         nodeQuery: |||
           sum by (<<.GroupBy>>) (
             1 - irate(
@@ -57,7 +58,7 @@ local defaults = {
               windows_cpu_time_total{mode="idle", job="windows-exporter",<<.LabelMatchers>>}[%(windowsExporter)s]
             )
           )
-        ||| % $.rangeIntervals,
+        ||| % { nodeExporter: $.rangeIntervals.nodeExporter, windowsExporter: $.rangeIntervals.windowsExporter, containerMetricsPrefix: $.containerMetricsPrefix },
         resources: {
           overrides: {
             node: { resource: 'node' },
@@ -70,9 +71,9 @@ local defaults = {
       memory: {
         containerQuery: |||
           sum by (<<.GroupBy>>) (
-            container_memory_working_set_bytes{<<.LabelMatchers>>,container!="",pod!=""}
+            %(containerMetricsPrefix)scontainer_memory_working_set_bytes{<<.LabelMatchers>>,container!="",pod!=""}
           )
-        |||,
+        ||| % { containerMetricsPrefix: $.containerMetricsPrefix },
         nodeQuery: |||
           sum by (<<.GroupBy>>) (
             node_memory_MemTotal_bytes{job="node-exporter",<<.LabelMatchers>>}
@@ -84,7 +85,7 @@ local defaults = {
             -
             windows_memory_available_bytes{job="windows-exporter",<<.LabelMatchers>>}
           )
-        |||,
+        ||| % { containerMetricsPrefix: $.containerMetricsPrefix },
         resources: {
           overrides: {
             instance: { resource: 'node' },