feat: add build_info metric (#121)

Signed-off-by: t3mi <t3mi@users.noreply.github.com>

.github/workflows/release.yml

@@ -43,3 +43,5 @@ jobs:
           platforms: linux/amd64,linux/arm64
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          build-args: |
+            VERSION=${{ steps.meta.outputs.version }}

Dockerfile

@@ -1,8 +1,11 @@
 FROM golang:1.20 AS builder
 
+ARG VERSION
+ENV PKG github.com/resmoio/kubernetes-event-exporter/pkg
+
 ADD . /app
 WORKDIR /app
-RUN CGO_ENABLED=0 GOOS=linux GO11MODULE=on go build -a -o /main .
+RUN CGO_ENABLED=0 GOOS=linux GO11MODULE=on go build -ldflags="-s -w -X ${PKG}/version.Version=${VERSION}" -a -o /main .
 
 FROM gcr.io/distroless/static:nonroot
 COPY --from=builder --chown=nonroot:nonroot /main /kubernetes-event-exporter

pkg/metrics/metrics.go

@@ -10,6 +10,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/exporter-toolkit/web"
+	"github.com/resmoio/kubernetes-event-exporter/pkg/version"
 	"github.com/rs/zerolog/log"
 )
 
@@ -18,6 +19,7 @@ type Store struct {
 	EventsDiscarded prometheus.Counter
 	WatchErrors     prometheus.Counter
 	SendErrors      prometheus.Counter
+	BuildInfo       prometheus.GaugeFunc
 }
 
 // promLogger implements promhttp.Logger
@@ -87,6 +89,20 @@ func Init(addr string, tlsConf string) {
 
 func NewMetricsStore(name_prefix string) *Store {
 	return &Store{
+		BuildInfo: promauto.NewGaugeFunc(
+			prometheus.GaugeOpts{
+				Name: name_prefix + "build_info",
+				Help: "A metric with a constant '1' value labeled by version, revision, branch, and goversion from which Kubernetes Event Exporter was built.",
+				ConstLabels: prometheus.Labels{
+					"version":   version.Version,
+					"revision":  version.Revision(),
+					"goversion": version.GoVersion,
+					"goos":      version.GoOS,
+					"goarch":    version.GoArch,
+				},
+			},
+			func() float64 { return 1 },
+		),
 		EventsProcessed: promauto.NewCounter(prometheus.CounterOpts{
 			Name: name_prefix + "events_sent",
 			Help: "The total number of events processed",
@@ -111,5 +127,6 @@ func DestroyMetricsStore(store *Store) {
 	prometheus.Unregister(store.EventsDiscarded)
 	prometheus.Unregister(store.WatchErrors)
 	prometheus.Unregister(store.SendErrors)
+	prometheus.Unregister(store.BuildInfo)
 	store = nil
 }

pkg/version/version.go

@@ -0,0 +1,29 @@
+package version
+
+import (
+	"runtime"
+	"runtime/debug"
+)
+
+// Build information. Populated at build-time.
+var (
+	Version   = "unknown"
+	GoVersion = runtime.Version()
+	GoOS      = runtime.GOOS
+	GoArch    = runtime.GOARCH
+)
+
+func Revision() string {
+	bi, ok := debug.ReadBuildInfo()
+
+	if ok {	
+		for _, kv := range bi.Settings {
+			switch kv.Key {
+				case "vcs.revision":
+					return kv.Value
+			}
+		}
+	}
+
+	return "unknown"
+}