app: log git commit hash (#368)

Logs git commit hash and time on startup. Also set commit hash metric and add to version command.

category: feature
ticket: #367

app/app.go

@@ -116,7 +116,12 @@ func Run(ctx context.Context, conf Config) (err error) {
 		return err
 	}
 
-	log.Info(ctx, "Charon starting", z.Str("version", version.Version))
+	hash, timestamp := GitCommit()
+	log.Info(ctx, "Charon starting",
+		z.Str("version", version.Version),
+		z.Str("git_commit_hash", hash),
+		z.Str("git_commit_time", timestamp),
+	)
 
 	// Wire processes and their dependencies
 	life := new(lifecycle.Manager)

app/metrics.go

@@ -16,6 +16,8 @@
 package app
 
 import (
+	"runtime/debug"
+
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 
@@ -29,6 +31,12 @@ var (
 		Help:      "Constant gauge with label set to current app version",
 	}, []string{"version"})
 
+	gitGauge = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: "app",
+		Name:      "git_commit",
+		Help:      "Constant gauge with label set to current git commit hash",
+	}, []string{"hash"})
+
 	startGauge = promauto.NewGauge(prometheus.GaugeOpts{
 		Namespace: "app",
 		Name:      "start_time_secs",
@@ -39,4 +47,27 @@ var (
 func initStartupMetrics() {
 	versionGauge.WithLabelValues(version.Version).Set(1)
 	startGauge.SetToCurrentTime()
+
+	hash, _ := GitCommit()
+	gitGauge.WithLabelValues(hash).Set(1)
+}
+
+// GitCommit returns the git commit hash and timestamp from build info.
+func GitCommit() (hash string, timestamp string) {
+	hash, timestamp = "unknown", "unknown"
+
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return hash, timestamp
+	}
+
+	for _, s := range info.Settings {
+		if s.Key == "vcs.revision" {
+			hash = s.Value[:7]
+		} else if s.Key == "vcs.time" {
+			timestamp = s.Value
+		}
+	}
+
+	return hash, timestamp
 }

cmd/version.go

@@ -23,6 +23,7 @@ import (
 	"github.com/spf13/cobra"
 	"github.com/spf13/pflag"
 
+	"github.com/obolnetwork/charon/app"
 	"github.com/obolnetwork/charon/app/version"
 )
 
@@ -53,7 +54,8 @@ func bindVersionFlags(flags *pflag.FlagSet, config *versionConfig) {
 }
 
 func runVersionCmd(out io.Writer, config versionConfig) {
-	_, _ = fmt.Fprintln(out, version.Version)
+	hash, timestamp := app.GitCommit()
+	_, _ = fmt.Fprintf(out, "%s [git_commit_hash=%s,git_commit_time=%s]\n", version.Version, hash, timestamp)
 
 	if !config.Verbose {
 		return