Properly include source version in the binary and expose in metrics

Due to golang being annoying the VCS version isn't recorded in
debug.ReadBuildInfo when using `go build`.

If you have too much time, see:
- golang/go#29228
- golang/go#50603

Author: ulope

rolling-shutter/Makefile

@@ -10,7 +10,7 @@ EXECUTABLE	?= ${BINDIR}/rolling-shutter
 GOPATH          ?= $(${GO} env GOPATH)
 
 build:
-	${GO} build ${GOFLAGS} -o ${EXECUTABLE}
+	${GO} build ${GOFLAGS} -ldflags="-X github.com/shutter-network/rolling-shutter/rolling-shutter/cmd/shversion.version=$(shell git describe --always --dirty)" -o ${EXECUTABLE}
 
 shcryptowasm: wasm
 	echo "The 'shcryptowasm' target is deprecated, use 'wasm' instead."
@@ -106,10 +106,10 @@ install-asdf-plugins:
 	../tools/asdf-install-plugins.sh
 
 install-asdf: install-asdf-plugins
-	# Various packages installed by asdf internally also use make and don't like if an external make has already
-	# tinkered with then environment.
-	# Therefore we unset MAKELEVEL here.
-	env -u MAKELEVEL asdf install
+	@# Various packages installed by asdf internally also use make and don't like if an external make has already
+	@# tinkered with then environment.
+	@# Therefore we unset MAKELEVEL here.
+	@env -u MAKELEVEL asdf install
 
 lint:
 	golangci-lint run --tests

rolling-shutter/cmd/shversion/shversion.go

@@ -8,10 +8,19 @@ import (
 	"runtime/debug"
 )
 
+// This gets set via ldflags when building via the Makefile
 var version string
 
 // Version returns shuttermint's version string.
 func Version() string {
+	var raceinfo string
+	if raceDetectorEnabled {
+		raceinfo = ", race detector enabled"
+	}
+	return fmt.Sprintf("%s (%s, %s-%s%s)", VersionShort(), runtime.Version(), runtime.GOOS, runtime.GOARCH, raceinfo)
+}
+
+func VersionShort() string {
 	if version == "" {
 		info, ok := debug.ReadBuildInfo()
 		if ok {
@@ -26,10 +35,5 @@ func Version() string {
 			}
 		}
 	}
-
-	var raceinfo string
-	if raceDetectorEnabled {
-		raceinfo = ", race detector enabled"
-	}
-	return fmt.Sprintf("%s (%s, %s-%s%s)", version, runtime.Version(), runtime.GOOS, runtime.GOARCH, raceinfo)
+	return version
 }

rolling-shutter/medley/metricsserver/metricsserver.go

@@ -7,15 +7,28 @@ import (
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/collectors"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/rs/zerolog/log"
 
+	"github.com/shutter-network/rolling-shutter/rolling-shutter/cmd/shversion"
 	"github.com/shutter-network/rolling-shutter/rolling-shutter/medley/service"
 )
 
+var metricsGoBuildInfo = prometheus.NewGauge(
+	prometheus.GaugeOpts{
+		Namespace: "go",
+		Subsystem: "build",
+		Name:      "info",
+		Help:      "A metric with a constant '1' value labeled by version from which the binary was built.",
+		ConstLabels: prometheus.Labels{
+			"version": shversion.VersionShort(),
+		},
+	},
+)
+
 func init() {
-	prometheus.MustRegister(collectors.NewBuildInfoCollector())
+	metricsGoBuildInfo.Set(1)
+	prometheus.MustRegister(metricsGoBuildInfo)
 }
 
 type MetricsServer struct {