Adds the pipelines metrics documentation

Fixes #1965

docs/README.md

@@ -54,6 +54,7 @@ See the following topics to learn how to use Tekton Pipelines in your project:
 - [Configuring authentication](auth.md)
 - [Using labels](labels.md)
 - [Viewing logs](logs.md)
+- [Pipelines metrics](metrics.md)
 
 ## Contributing to Tekton Pipelines
 

docs/metrics.md

@@ -0,0 +1,17 @@
+# Pipeline Controller Metrics
+
+Following pipeline metrics are exposed at `controller-service` on port `9090`
+
+There are different kinds of exporters available: Prometheus, Google Stackdriver, etc. They can be configured 
+using [observability configuration](../config/config-observability.yaml). 
+
+| Metric name| Metric type | Labels/tags | Status |
+| ---------- | ----------- | ----------- | ----------- |
+| tekton_pipelinerun_duration_seconds_[bucket, sum, count] | Histogram | `pipeline`=&lt;pipeline_name&gt; <br> `pipelinerun`=&lt;pipelinerun_name&gt; <br> `status`=&lt;status&gt; <br> `namespace`=&lt;pipelinerun-namespace&gt; | experimental |
+| tekton_pipelinerun_taskrun_duration_seconds_[bucket, sum, count] | Histogram | `pipeline`=&lt;pipeline_name&gt; <br> `pipelinerun`=&lt;pipelinerun_name&gt; <br> `status`=&lt;status&gt; <br> `task`=&lt;task_name&gt; <br> `taskrun`=&lt;taskrun_name&gt;<br> `namespace`=&lt;pipelineruns-taskruns-namespace&gt;| experimental |
+| tekton_pipelinerun_count| Counter | `status`=&lt;status&gt; | experimental |
+| tekton_running_pipelineruns_count | Gauge | | experimental | 
+| tekton_taskrun_duration_seconds_[bucket, sum, count] | Histogram | `status`=&lt;status&gt; <br> `task`=&lt;task_name&gt; <br> `taskrun`=&lt;taskrun_name&gt;<br> `namespace`=&lt;pipelineruns-taskruns-namespace&gt; | experimental | 
+| tekton_taskrun_count | Counter | `status`=&lt;status&gt; | experimental | 
+| tekton_running_taskruns_count | Gauge | | experimental |
+| tekton_taskruns_pod_latency | Gauge | `namespace`=&lt;taskruns-namespace&gt; <br> `pod`= &lt; taskrun_pod_name&gt; <br> `task`=&lt;task_name&gt; <br> `taskrun`=&lt;taskrun_name&gt;<br> | experimental |