add the version/build_info stuff

Makefile

@@ -1,13 +1,32 @@
-.PHONY: clean run
+##
+#
+.DEFAULT_GOAL := help
 
-linux:
-	GOOS=linux GOARCH=amd64 go build -o output/mystrom-exporter_linux-amd64
-mac:
-	GOOS=darwin GOARCH=amd64 go build -o output/mystrom-exporter_mac-amd64
+version    := $(shell git describe --tags --always)
+revision   := $(shell git rev-parse HEAD)
+branch     := $(shell git rev-parse --abbrev-ref HEAD)
+builduser  := $(shell whoami)
+builddate  := $(shell date '+%FT%T_%Z')
+
+versionPkgPrefix := mystrom-exporter/pkg/version
+
+LDFLAGS   := -w -s \
+	-X $(versionPkgPrefix).Version=${version} \
+	-X $(versionPkgPrefix).Revision=${revision} \
+	-X $(versionPkgPrefix).Branch=${branch} \
+	-X $(versionPkgPrefix).BuildUser=${builduser} \
+	-X $(versionPkgPrefix).BuildDate=${builddate}
+GOFLAGS   := -v
+
+linux: ## builds the linux version of the exporter
+	GOOS=linux GOARCH=amd64 go build $(GOFLAGS) -ldflags '$(LDFLAGS)'
+mac: ## builds the macos version of the exporter
+	GOOS=darwin GOARCH=amd64 go build $(GOFLAGS) -ldflags '$(LDFLAGS)'
 arm64:
-	GOOS=linux GOARCH=arm64 go build -o output/mystrom-exporter_linux-arm64
+	GOOS=linux GOARCH=arm64 go build $(GOFLAGS) -ldflags '$(LDFLAGS)'
 arm:
-	GOOS=linux GOARCH=arm go build -o output/mystrom-exporter_linux-arm
+	GOOS=linux GOARCH=arm go build $(GOFLAGS) -ldflags '$(LDFLAGS)'
 
-
-all: linux mac arm64 arm
+# --
+help:
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST)  | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'

main.go

@@ -12,6 +12,8 @@ import (
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
+
+	"mystrom-exporter/pkg/version"
 )
 
 type switchReport struct {
@@ -30,6 +32,8 @@ var (
 		"Path under which to expose metrics")
 	switchIP = flag.String("switch.ip-address", "",
 		"IP address of the switch you try to monitor")
+	showVersion = flag.Bool("version", false,
+		"Show version information.")
 
 	up = prometheus.NewDesc(
 		prometheus.BuildFQName(namespace, "", "up"),
@@ -169,14 +173,36 @@ func main() {
 
 	flag.Parse()
 
+	// Show version information
+	if *showVersion {
+		v, err := version.Print("mystrom_exporter")
+		if err != nil {
+			log.Fatalf("Failed to print version information: %#v", err)
+		}
+
+		fmt.Fprintln(os.Stdout, v)
+		os.Exit(0)
+	}
+
 	if *switchIP == "" {
 		flag.Usage()
 		fmt.Println("\nNo switch.ip-address provided")
 		os.Exit(1)
 	}
 
+	// make the build information is available through a metric
+	buildInfo := prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: "scripts",
+			Name:      "build_info",
+			Help:      "A metric with a constant '1' value labeled by build information.",
+		},
+		[]string{"version", "revision", "branch", "goversion", "builddate", "builduser"},
+	)
+	buildInfo.WithLabelValues(version.Version, version.Revision, version.Branch, version.GoVersion, version.BuildDate, version.BuildUser).Set(1)
+
 	exporter := NewExporter(*switchIP)
-	prometheus.MustRegister(exporter)
+	prometheus.MustRegister(exporter, buildInfo)
 
 	http.Handle(*metricsPath, promhttp.Handler())
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {

pkg/version/version.go

@@ -0,0 +1,60 @@
+package version
+
+import (
+	"bytes"
+	"fmt"
+	"runtime"
+	"strings"
+	"text/template"
+)
+
+// Build information. Populated at build-time.
+var (
+	Version   string
+	Revision  string
+	Branch    string
+	BuildUser string
+	BuildDate string
+	GoVersion = runtime.Version()
+)
+
+// versionInfoTmpl contains the template used by Print.
+var versionInfoTmpl = `
+{{.program}}, version {{.version}} (branch: {{.branch}}, revision: {{.revision}})
+  build user:       {{.buildUser}}
+  build date:       {{.buildDate}}
+  go version:       {{.goVersion}}
+`
+
+// Print returns version information.
+func Print(program string) (string, error) {
+	m := map[string]string{
+		"program":   program,
+		"version":   Version,
+		"revision":  Revision,
+		"branch":    Branch,
+		"buildUser": BuildUser,
+		"buildDate": BuildDate,
+		"goVersion": GoVersion,
+	}
+	t, err := template.New("version").Parse(versionInfoTmpl)
+	if err != nil {
+		return "", err
+	}
+
+	var buf bytes.Buffer
+	if err := t.ExecuteTemplate(&buf, "version", m); err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(buf.String()), nil
+}
+
+// Info returns version, branch and revision information.
+func Info() string {
+	return fmt.Sprintf("(version=%s, branch=%s, revision=%s)", Version, Branch, Revision)
+}
+
+// BuildContext returns goVersion, buildUser and buildDate information.
+func BuildContext() string {
+	return fmt.Sprintf("(go=%s, user=%s, date=%s)", GoVersion, BuildUser, BuildDate)
+}