added example of provided metrics and sample

Author: pgodowski

README.md

@@ -10,20 +10,51 @@ A Docker image is available at: `quay.io/brancz/prometheus-example-app:v0.3.0`
 
 First, deploy one instance of this example application, which listens and exposes metrics on port 8080 using the following [Deployment manifest](manifests/deployment.yaml).
 
-Then, in order for Prometheus to be able to discover and scrape these metrics, in this repository we provide [Pod Monitor][prometheus-operator-crd] custom resource as an example. For that, Prometheus Operator needs to be running in the cluster. To install it, follow this guide: [quickstart][prometheus-operator-quickstart].
+Then, in order for Prometheus to be able to discover and scrape these metrics, in this repository we provide [Pod Monitor][prometheus-operator-crd] custom resource as an example. For that, [Prometheus Operator][prometheus-operator] needs to be running in the cluster. To install it, follow this guide: [quickstart][prometheus-operator-quickstart].
 
 For this example application, [PodMonitor manifest](manifests/pod-monitor.yaml) describes how the metrics can be discovered and scrapped by Prometheus.
 
 [prometheus]:https://prometheus.io/
 [client-golang]:https://github.com/prometheus/client_golang
+[prometheus-operator]:https://github.com/prometheus-operator/prometheus-operator
 [prometheus-operator-quickstart]:https://github.com/coreos/prometheus-operator#quickstart
 [prometheus-operator-crd]:https://github.com/coreos/prometheus-operator#customresourcedefinitions
 
 ## Exposed Prometheus metrics
 
-This example app exposed the following data over the `/metrics` API, resulting with the `version` metric being collected and exposed in Prometheus.
+The following metrics are exposed:
+
+- `version` - of type _gauge_ - containing the app version - as a constant metric value `1` and label `version`, representing this app version
+- `http_requests_total` - of type _counter_ - representing the total numbere of incoming HTTP requests
+- `http_request_duration_seconds` - of type _histogram_, representing duration of all HTTP requests
+- `http_request_duration_seconds_count`- total count of all incoming HTTP requeests
+- `http_request_duration_seconds_sum` - total duration in seconds of all incoming HTTP requests
+- `http_request_duration_seconds_bucket` - a histogram representation of the duration of the incoming HTTP requests
+
+The sample output of the `/metric` endpoint after 5 incoming HTTP requests shown below.
+
+Note: with no initial incoming request, only `version` metric is reported.
 
 ```
+# HELP http_request_duration_seconds Duration of all HTTP requests
+# TYPE http_request_duration_seconds histogram
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="0.005"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="0.01"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="0.025"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="0.05"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="0.1"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="0.25"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="0.5"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="1"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="2.5"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="5"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="10"} 5
+http_request_duration_seconds_bucket{code="200",handler="found",method="get",le="+Inf"} 5
+http_request_duration_seconds_sum{code="200",handler="found",method="get"} 0.00047495999999999997
+http_request_duration_seconds_count{code="200",handler="found",method="get"} 5
+# HELP http_requests_total Count of all HTTP requests
+# TYPE http_requests_total counter
+http_requests_total{code="200",method="get"} 5
 # HELP version Version information about this binary
 # TYPE version gauge
 version{version="v0.3.0"} 1