add build info metrics (#7525)

* add build info metrics

* unused

* metrics on build

* size limit

* once

3 files changed, 112 insertions, 2 deletions

diff --git a/weed/stats/metrics.go b/weed/stats/metrics.go
index 2723e253f..95491abf1 100644
--- a/weed/stats/metrics.go
+++ b/weed/stats/metrics.go
@@ -4,6 +4,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"runtime"
 	"strconv"
 	"strings"
 	"sync"
@@ -16,6 +17,19 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 )
 
+// SetVersionInfo sets the version information for the BuildInfo metric
+// This is called by the version package during initialization.
+// It uses sync.Once to ensure the build information is set only once,
+// making it safe to call multiple times while ensuring immutability.
+var SetVersionInfo = func() func(string, string, string) {
+	var once sync.Once
+	return func(version, commitHash, sizeLimit string) {
+		once.Do(func() {
+			BuildInfo.WithLabelValues(version, commitHash, sizeLimit, runtime.GOOS, runtime.GOARCH).Set(1)
+		})
+	}
+}()
+
 // Readonly volume types
 const (
 	Namespace        = "SeaweedFS"
@@ -26,14 +40,20 @@ const (
 	bucketAtiveTTL   = 10 * time.Minute
 )
 
-var readOnlyVolumeTypes = [4]string{IsReadOnly, NoWriteOrDelete, NoWriteCanDelete, IsDiskSpaceLow}
-
 var bucketLastActiveTsNs map[string]int64 = map[string]int64{}
 var bucketLastActiveLock sync.Mutex
 
 var (
 	Gather = prometheus.NewRegistry()
 
+	BuildInfo = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: Namespace,
+			Subsystem: "build",
+			Name:      "info",
+			Help:      "A metric with a constant '1' value labeled by version, commit, sizelimit, goos, and goarch from which SeaweedFS was built.",
+		}, []string{"version", "commit", "sizelimit", "goos", "goarch"})
+
 	MasterClientConnectCounter = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Namespace: Namespace,
@@ -385,6 +405,8 @@ var (
 )
 
 func init() {
+	Gather.MustRegister(BuildInfo)
+
 	Gather.MustRegister(MasterClientConnectCounter)
 	Gather.MustRegister(MasterRaftIsleader)
 	Gather.MustRegister(MasterAdminLock)
diff --git a/weed/stats/metrics_buildinfo_test.go b/weed/stats/metrics_buildinfo_test.go
new file mode 100644
index 000000000..1fc4a2b52
--- /dev/null
+++ b/weed/stats/metrics_buildinfo_test.go
@@ -0,0 +1,82 @@
+package stats_test
+
+import (
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus/testutil"
+	"github.com/seaweedfs/seaweedfs/weed/stats"
+	_ "github.com/seaweedfs/seaweedfs/weed/util/version" // Import to trigger version init
+)
+
+func TestBuildInfo(t *testing.T) {
+	// Verify that BuildInfo metric is registered and has the expected value
+	count := testutil.CollectAndCount(stats.BuildInfo)
+	if count != 1 {
+		t.Errorf("Expected 1 BuildInfo metric, got %d", count)
+	}
+
+	// Verify the metric can be gathered
+	metrics, err := stats.Gather.Gather()
+	if err != nil {
+		t.Fatalf("Failed to gather metrics: %v", err)
+	}
+
+	// Find the build_info metric
+	found := false
+	for _, mf := range metrics {
+		if mf.GetName() == "SeaweedFS_build_info" {
+			found = true
+			metric := mf.GetMetric()[0]
+			
+			// Verify the metric value is 1
+			if metric.GetGauge().GetValue() != 1 {
+				t.Errorf("Expected BuildInfo value to be 1, got %f", metric.GetGauge().GetValue())
+			}
+
+			// Verify labels exist
+			labels := metric.GetLabel()
+			labelMap := make(map[string]string)
+			for _, label := range labels {
+				labelMap[label.GetName()] = label.GetValue()
+			}
+
+			// Check required labels
+			if _, ok := labelMap["version"]; !ok {
+				t.Error("Missing 'version' label")
+			}
+			if _, ok := labelMap["commit"]; !ok {
+				t.Error("Missing 'commit' label")
+			}
+			if _, ok := labelMap["sizelimit"]; !ok {
+				t.Error("Missing 'sizelimit' label")
+			}
+			if labelMap["goos"] != runtime.GOOS {
+				t.Errorf("Expected goos='%s', got '%s'", runtime.GOOS, labelMap["goos"])
+			}
+			if labelMap["goarch"] != runtime.GOARCH {
+				t.Errorf("Expected goarch='%s', got '%s'", runtime.GOARCH, labelMap["goarch"])
+			}
+
+			// Verify version format
+			if !strings.Contains(labelMap["version"], ".") {
+				t.Errorf("Version should contain a dot: %s", labelMap["version"])
+			}
+
+			// Verify sizelimit is either 30GB or 8000GB
+			if labelMap["sizelimit"] != "30GB" && labelMap["sizelimit"] != "8000GB" {
+				t.Errorf("Expected sizelimit to be '30GB' or '8000GB', got '%s'", labelMap["sizelimit"])
+			}
+
+			t.Logf("BuildInfo metric: version=%s, commit=%s, sizelimit=%s, goos=%s, goarch=%s",
+				labelMap["version"], labelMap["commit"], labelMap["sizelimit"],
+				labelMap["goos"], labelMap["goarch"])
+		}
+	}
+
+	if !found {
+		t.Error("BuildInfo metric not found in gathered metrics")
+	}
+}
+
diff --git a/weed/util/version/constants.go b/weed/util/version/constants.go
index 33b226202..8cbe2225a 100644
--- a/weed/util/version/constants.go
+++ b/weed/util/version/constants.go
@@ -3,6 +3,7 @@ package version
 import (
 	"fmt"
 
+	"github.com/seaweedfs/seaweedfs/weed/stats"
 	"github.com/seaweedfs/seaweedfs/weed/util"
 )
 
@@ -14,6 +15,11 @@ var (
 	COMMIT         = ""
 )
 
+func init() {
+	// Set version info in stats for Prometheus metrics
+	stats.SetVersionInfo(VERSION_NUMBER, COMMIT, util.SizeLimit)
+}
+
 func Version() string {
 	return VERSION + " " + COMMIT
 }