add certificate issue duration metrics

proxy/internal/acme/manager.go

@@ -42,6 +42,10 @@ type domainInfo struct {
 	err       string
 }
 
+type metricsRecorder interface {
+	RecordCertificateIssuance(duration time.Duration)
+}
+
 // Manager wraps autocert.Manager with domain tracking and cross-replica
 // coordination via a pluggable locking strategy. The locker prevents
 // duplicate ACME requests when multiple replicas share a certificate cache.
@@ -55,6 +59,7 @@ type Manager struct {
 
 	certNotifier certificateNotifier
 	logger       *log.Logger
+	metrics      metricsRecorder
 }
 
 // NewManager creates a new ACME certificate manager. The certDir is used
@@ -63,7 +68,7 @@ type Manager struct {
 // eabKID and eabHMACKey are optional External Account Binding credentials
 // required for some CAs like ZeroSSL. The eabHMACKey should be the base64
 // URL-encoded string provided by the CA.
-func NewManager(certDir, acmeURL, eabKID, eabHMACKey string, notifier certificateNotifier, logger *log.Logger, lockMethod CertLockMethod) *Manager {
+func NewManager(certDir, acmeURL, eabKID, eabHMACKey string, notifier certificateNotifier, logger *log.Logger, lockMethod CertLockMethod, metrics metricsRecorder) *Manager {
 	if logger == nil {
 		logger = log.StandardLogger()
 	}
@@ -73,6 +78,7 @@ func NewManager(certDir, acmeURL, eabKID, eabHMACKey string, notifier certificat
 		domains:      make(map[domain.Domain]*domainInfo),
 		certNotifier: notifier,
 		logger:       logger,
+		metrics:      metrics,
 	}
 
 	var eab *acme.ExternalAccountBinding
@@ -161,6 +167,10 @@ func (mgr *Manager) prefetchCertificate(d domain.Domain) {
 		return
 	}
 
+	if mgr.metrics != nil {
+		mgr.metrics.RecordCertificateIssuance(elapsed)
+	}
+
 	mgr.setDomainState(d, domainReady, "")
 
 	now := time.Now()

proxy/internal/acme/manager_test.go

@@ -10,7 +10,7 @@ import (
 )
 
 func TestHostPolicy(t *testing.T) {
-	mgr := NewManager(t.TempDir(), "https://acme.example.com/directory", "", "", nil, nil, "")
+	mgr := NewManager(t.TempDir(), "https://acme.example.com/directory", "", "", nil, nil, "", nil)
 	mgr.AddDomain("example.com", "acc1", "rp1")
 
 	// Wait for the background prefetch goroutine to finish so the temp dir
@@ -70,7 +70,7 @@ func TestHostPolicy(t *testing.T) {
 }
 
 func TestDomainStates(t *testing.T) {
-	mgr := NewManager(t.TempDir(), "https://acme.example.com/directory", "", "", nil, nil, "")
+	mgr := NewManager(t.TempDir(), "https://acme.example.com/directory", "", "", nil, nil, "", nil)
 
 	assert.Equal(t, 0, mgr.PendingCerts(), "initially zero")
 	assert.Equal(t, 0, mgr.TotalDomains(), "initially zero domains")

proxy/internal/metrics/metrics.go

@@ -13,13 +13,14 @@ import (
 )
 
 type Metrics struct {
-	ctx               context.Context
-	requestsTotal     metric.Int64Counter
-	activeRequests    metric.Int64UpDownCounter
-	configuredDomains metric.Int64UpDownCounter
-	totalPaths        metric.Int64UpDownCounter
-	requestDuration   metric.Int64Histogram
-	backendDuration   metric.Int64Histogram
+	ctx                      context.Context
+	requestsTotal            metric.Int64Counter
+	activeRequests           metric.Int64UpDownCounter
+	configuredDomains        metric.Int64UpDownCounter
+	totalPaths               metric.Int64UpDownCounter
+	requestDuration          metric.Int64Histogram
+	backendDuration          metric.Int64Histogram
+	certificateIssueDuration metric.Int64Histogram
 
 	mappingsMux  sync.Mutex
 	mappingPaths map[string]int
@@ -80,15 +81,25 @@ func New(ctx context.Context, meter metric.Meter) (*Metrics, error) {
 		return nil, err
 	}
 
+	certificateIssueDuration, err := meter.Int64Histogram(
+		"proxy.certificate.issue.duration.ms",
+		metric.WithUnit("milliseconds"),
+		metric.WithDescription("Duration of ACME certificate issuance"),
+	)
+	if err != nil {
+		return nil, err
+	}
+
 	return &Metrics{
-		ctx:               ctx,
-		requestsTotal:     requestsTotal,
-		activeRequests:    activeRequests,
-		configuredDomains: configuredDomains,
-		totalPaths:        totalPaths,
-		requestDuration:   requestDuration,
-		backendDuration:   backendDuration,
-		mappingPaths:      make(map[string]int),
+		ctx:                      ctx,
+		requestsTotal:            requestsTotal,
+		activeRequests:           activeRequests,
+		configuredDomains:        configuredDomains,
+		totalPaths:               totalPaths,
+		requestDuration:          requestDuration,
+		backendDuration:          backendDuration,
+		certificateIssueDuration: certificateIssueDuration,
+		mappingPaths:             make(map[string]int),
 	}, nil
 }
 
@@ -179,3 +190,8 @@ func (m *Metrics) RemoveMapping(mapping proxy.Mapping) {
 
 	delete(m.mappingPaths, mapping.Host)
 }
+
+// RecordCertificateIssuance records the duration of a certificate issuance.
+func (m *Metrics) RecordCertificateIssuance(duration time.Duration) {
+	m.certificateIssueDuration.Record(m.ctx, duration.Milliseconds())
+}