feat(main): add 5xx counter metrics

Signed-off-by: Rick Rackow <[email protected]>

Author: RiRa12621

README.md

@@ -2,7 +2,13 @@
 
 This example app serves as an example of how one can easily instrument HTTP handlers with [Prometheus][prometheus] metrics. It uses the Prometheus [go client][client-golang] to create a new Prometheus registry.
 
-Usage is simple, on any request to `/` the request will result in a `200` response code. This increments the counter for this response code. Similarly the `/err` endpoint will result in a `404` response code, therefore increments that respective counter. Duration metrics are also exposed for any request to `/`.
+Usage is simple, on any request to `/` the request will result in a `200` 
+response code. This increments the counter for this response code. Similarly, 
+the `/404` endpoint will result in a `404` response code, therefore 
+increments that respective counter. Any request to `/500` will increment the 
+respective counter for errors. 
+
+Duration metrics are also exposed for any request to `/`.
 
 A Docker image is available at: `ghcr.io/rhobs/prometheus-example-app:0.3.0`
 
@@ -25,9 +31,9 @@ For this example application, [PodMonitor manifest](manifests/pod-monitor.yaml)
 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_requests_total` - of type _counter_ - representing the total number 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_count`- total count of all incoming HTTP requests
 - `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
 

main.go

@@ -54,6 +54,9 @@ func main() {
 	notfoundHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusNotFound)
 	})
+	errHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+	})
 
 	foundChain := promhttp.InstrumentHandlerDuration(
 		httpRequestDuration.MustCurryWith(prometheus.Labels{"handler": "found"}),
@@ -62,8 +65,9 @@ func main() {
 
 	mux := http.NewServeMux()
 	mux.Handle("/", foundChain)
-	mux.Handle("/err", promhttp.InstrumentHandlerCounter(httpRequestsTotal, notfoundHandler))
+	mux.Handle("/404", promhttp.InstrumentHandlerCounter(httpRequestsTotal, notfoundHandler))
 	mux.Handle("/metrics", promhttp.HandlerFor(r, promhttp.HandlerOpts{}))
+	mux.Handle("/500", promhttp.InstrumentHandlerCounter(httpRequestsTotal, errHandler))
 
 	var srv *http.Server
 	if enableH2c {

manifests/all-in-one.yaml

@@ -0,0 +1,59 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: ns1
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app: prometheus-example-app
+  name: prometheus-example-app
+  namespace: ns1
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: prometheus-example-app
+  template:
+    metadata:
+      labels:
+        app: prometheus-example-app
+    spec:
+      containers:
+        - image: ghcr.io/rhobs/prometheus-example-app:0.4.0
+          imagePullPolicy: IfNotPresent
+          name: prometheus-example-app
+---
+apiVersion: v1
+kind: Service
+metadata:
+  labels:
+    app: prometheus-example-app
+  name: prometheus-example-app
+  namespace: ns1
+spec:
+  ports:
+    - port: 8080
+      protocol: TCP
+      targetPort: 8080
+      name: web
+  selector:
+    app: prometheus-example-app
+  type: ClusterIP
+---
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  labels:
+    k8s-app: prometheus-example-monitor
+  name: prometheus-example-monitor
+  namespace: ns1
+spec:
+  endpoints:
+    - interval: 30s
+      port: web
+      scheme: http
+  selector:
+    matchLabels:
+      app: prometheus-example-app