feat(node): add morphnode_info metrics gauge

node/cmd/node/main.go

@@ -37,6 +37,7 @@ import (
 	"morph-l2/node/sequencer/mock"
 	"morph-l2/node/sync"
 	"morph-l2/node/types"
+	"morph-l2/node/version"
 )
 
 func main() {
@@ -81,6 +82,12 @@ func L2NodeMain(ctx *cli.Context) error {
 		return err
 	}
 
+	// Publish build/version metadata as morphnode_info{...} 1 (mirrors morph-reth's
+	// reth_info{} gauge). Registers on the default Prometheus registry, so it's
+	// exposed regardless of which branch below brings up /metrics (own listener in
+	// layer1-verify mode, or Tendermint's instrumentation in every other mode).
+	version.PrometheusMetrics("morphnode", Version, GitCommit, BuildTime).Register()
+
 	// Wire the centralized-sequencer upgrade time into the consensus upgrade package before any
 	// consensus / blocksync routine runs. A user-provided --sequencerUpgradeTime wins. If it is
 	// absent, --mainnet / --hoodi selects the corresponding network default. With no network and no

node/go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/morph-l2/go-ethereum v1.10.14-0.20260908092055-4012f174b967
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.17.0
+	github.com/prometheus/client_model v0.5.0
 	github.com/spf13/viper v1.13.0
 	github.com/stretchr/testify v1.10.0
 	github.com/syndtr/goleveldb v1.0.1-0.20220614013038-64ee5596c38a
@@ -98,7 +99,6 @@ require (
 	github.com/pelletier/go-toml/v2 v2.0.5 // indirect
 	github.com/petermattis/goid v0.0.0-20231207134359-e60b3f734c67 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
-	github.com/prometheus/client_model v0.5.0 // indirect
 	github.com/prometheus/common v0.45.0 // indirect
 	github.com/prometheus/procfs v0.12.0 // indirect
 	github.com/prometheus/tsdb v0.10.0 // indirect

node/version/metrics.go

@@ -0,0 +1,54 @@
+// Package version exposes morphnode's build/version metadata as a Prometheus
+// info-style gauge, mirroring morph-reth's reth_info{} gauge: a static gauge
+// permanently set to 1, whose Prometheus labels (not its value) carry the
+// actual information. Scraping tools use this to build a "which build/version
+// is running where" view (e.g. `max by (version) (morphnode_info{})`).
+package version
+
+import (
+	"runtime"
+
+	"github.com/go-kit/kit/metrics"
+	"github.com/go-kit/kit/metrics/discard"
+	"github.com/go-kit/kit/metrics/prometheus"
+	stdprometheus "github.com/prometheus/client_golang/prometheus"
+)
+
+// Info is a static Prometheus gauge carrying morphnode's build metadata as
+// labels. Its value is always 1; only the labels are meaningful.
+type Info struct {
+	gauge metrics.Gauge
+}
+
+// PrometheusMetrics registers the morphnode_info gauge on the default
+// Prometheus registry under the given namespace (no subsystem: the resulting
+// metric name is "<namespace>_info", e.g. "morphnode_info"). version,
+// gitCommit and buildTime should be the values injected via -ldflags at build
+// time (see cmd/node/version.go); goVersion/os/arch are read from the runtime.
+func PrometheusMetrics(namespace, version, gitCommit, buildTime string) *Info {
+	labels := []string{"version", "git_commit", "build_time", "go_version", "os", "arch"}
+	g := prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
+		Namespace: namespace,
+		Name:      "info",
+		Help:      "Static info metric (always 1) carrying morphnode build/version metadata as labels.",
+	}, labels).With(
+		"version", version,
+		"git_commit", gitCommit,
+		"build_time", buildTime,
+		"go_version", runtime.Version(),
+		"os", runtime.GOOS,
+		"arch", runtime.GOARCH,
+	)
+	return &Info{gauge: g}
+}
+
+// NopMetrics returns an Info that discards its observation (no registration).
+// Mirrors the NopMetrics helpers used by the other metrics packages (e.g.
+// hakeeper.NopMetrics) for tests that don't need a live Prometheus registry.
+func NopMetrics() *Info {
+	return &Info{gauge: discard.NewGauge()}
+}
+
+// Register sets the gauge to 1, publishing the labels attached at
+// construction time. Call once at startup.
+func (i *Info) Register() { i.gauge.Set(1) }

node/version/metrics_test.go

@@ -0,0 +1,53 @@
+package version
+
+import (
+	"testing"
+
+	stdprometheus "github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/stretchr/testify/require"
+)
+
+// TestPrometheusMetrics_RegistersInfoGaugeSetToOne verifies that Register
+// publishes a single gauge, always valued 1, carrying the build metadata
+// passed to PrometheusMetrics as labels.
+func TestPrometheusMetrics_RegistersInfoGaugeSetToOne(t *testing.T) {
+	// Scoped per-test namespace: dodges "duplicate metrics collector
+	// registration" panics against the shared default registry, matching the
+	// pattern used in derivation/base_client_test.go.
+	namespace := "morphnode_test_" + t.Name()
+
+	info := PrometheusMetrics(namespace, "v1.2.3", "abc1234", "2026-09-22T00:00:00Z")
+	info.Register()
+
+	mfs, err := stdprometheus.DefaultGatherer.Gather()
+	require.NoError(t, err)
+
+	var found *dto.Metric
+	for _, mf := range mfs {
+		if mf.GetName() == namespace+"_info" {
+			require.Len(t, mf.GetMetric(), 1)
+			found = mf.GetMetric()[0]
+			break
+		}
+	}
+	require.NotNil(t, found, "expected %s_info gauge to be registered", namespace)
+	require.Equal(t, float64(1), found.GetGauge().GetValue())
+
+	labels := map[string]string{}
+	for _, l := range found.GetLabel() {
+		labels[l.GetName()] = l.GetValue()
+	}
+	require.Equal(t, "v1.2.3", labels["version"])
+	require.Equal(t, "abc1234", labels["git_commit"])
+	require.Equal(t, "2026-09-22T00:00:00Z", labels["build_time"])
+	require.NotEmpty(t, labels["go_version"])
+	require.NotEmpty(t, labels["os"])
+	require.NotEmpty(t, labels["arch"])
+}
+
+// TestNopMetrics_DoesNotPanic verifies NopMetrics().Register() is a safe
+// no-op, for callers (e.g. tests) that don't want a live Prometheus registry.
+func TestNopMetrics_DoesNotPanic(t *testing.T) {
+	require.NotPanics(t, func() { NopMetrics().Register() })
+}