From aaee0c126b8aef480489f157eab34bdacaf92499 Mon Sep 17 00:00:00 2001
From: Jakob Borg <jakob@kastelo.net>
Date: Tue, 14 Nov 2023 09:31:53 +0100
Subject: [PATCH] cmd/stdiscorv: Expose build info in metrics

---
 cmd/stdiscosrv/main.go  |  3 +++
 cmd/stdiscosrv/stats.go | 11 ++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/cmd/stdiscosrv/main.go b/cmd/stdiscosrv/main.go
index 79a63d63a..f7f968c86 100644
--- a/cmd/stdiscosrv/main.go
+++ b/cmd/stdiscosrv/main.go
@@ -14,6 +14,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"runtime"
 	"strings"
 	"time"
 
@@ -102,6 +103,8 @@ func main() {
 		return
 	}
 
+	buildInfo.WithLabelValues(build.Version, runtime.Version(), build.User, build.Date.UTC().Format("2006-01-02T15:04:05Z")).Set(1)
+
 	if largeDB {
 		levelDBOptions.BlockCacheCapacity = 64 << 20
 		levelDBOptions.BlockSize = 64 << 10
diff --git a/cmd/stdiscosrv/stats.go b/cmd/stdiscosrv/stats.go
index c466e09d2..949a369eb 100644
--- a/cmd/stdiscosrv/stats.go
+++ b/cmd/stdiscosrv/stats.go
@@ -14,6 +14,14 @@ import (
 )
 
 var (
+	buildInfo = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: "syncthing",
+			Subsystem: "discovery",
+			Name:      "build_info",
+			Help:      "A metric with a constant '1' value labeled by version, goversion, builduser and builddate from which stdiscosrv was built.",
+		}, []string{"version", "goversion", "builduser", "builddate"})
+
 	apiRequestsTotal = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Namespace: "syncthing",
@@ -112,7 +120,8 @@ const (
 )
 
 func init() {
-	prometheus.MustRegister(apiRequestsTotal, apiRequestsSeconds,
+	prometheus.MustRegister(buildInfo,
+		apiRequestsTotal, apiRequestsSeconds,
 		lookupRequestsTotal, announceRequestsTotal,
 		replicationSendsTotal, replicationRecvsTotal,
 		databaseKeys, databaseStatisticsSeconds,