telemetry: add a metric for agent TLS cert expiry

.changelog/10768.txt

@@ -0,0 +1,4 @@
+```release-note:improvement
+telemetry: add a new `agent.tls.cert.expiry` metric for tracking when the Agent TLS certificate expires.
+```
+

agent/agent.go

@@ -639,6 +639,11 @@ func (a *Agent) Start(ctx context.Context) error {
 		a.logger.Warn("DEPRECATED Backwards compatibility with pre-1.9 metrics enabled. These metrics will be removed in a future version of Consul. Set `telemetry { disable_compat_1.9 = true }` to disable them.")
 	}
 
+	if a.tlsConfigurator.Cert() != nil {
+		m := consul.AgentTLSCertExpirationMonitor(a.tlsConfigurator, a.logger, a.config.Datacenter)
+		go m.Monitor(&lib.StopChannelContext{StopCh: a.shutdownCh})
+	}
+
 	// consul version metric with labels
 	metrics.SetGaugeWithLabels([]string{"version"}, 1, []metrics.Label{
 		{Name: "version", Value: a.config.Version},

agent/consul/leader_connect.go

@@ -34,8 +34,8 @@ func (s *Server) startConnectLeader(ctx context.Context) error {
 
 	s.caManager.Start(ctx)
 	s.leaderRoutineManager.Start(ctx, caRootPruningRoutineName, s.runCARootPruning)
-	s.leaderRoutineManager.Start(ctx, caRootMetricRoutineName, rootCAExpiryMonitor(s).monitor)
+	s.leaderRoutineManager.Start(ctx, caRootMetricRoutineName, rootCAExpiryMonitor(s).Monitor)
-	s.leaderRoutineManager.Start(ctx, caSigningMetricRoutineName, signingCAExpiryMonitor(s).monitor)
+	s.leaderRoutineManager.Start(ctx, caSigningMetricRoutineName, signingCAExpiryMonitor(s).Monitor)
 
 	return s.startIntentionConfigEntryMigration(ctx)
 }

agent/consul/leader_metrics.go

@@ -2,18 +2,19 @@ package consul
 
 import (
 	"context"
+	"crypto/x509"
 	"errors"
 	"fmt"
 	"time"
 
-	"github.com/hashicorp/consul/agent/connect/ca"
-
-	"github.com/hashicorp/consul/agent/connect"
-
 	"github.com/armon/go-metrics"
 	"github.com/armon/go-metrics/prometheus"
-	"github.com/hashicorp/consul/logging"
 	"github.com/hashicorp/go-hclog"
+
+	"github.com/hashicorp/consul/agent/connect"
+	"github.com/hashicorp/consul/agent/connect/ca"
+	"github.com/hashicorp/consul/logging"
+	"github.com/hashicorp/consul/tlsutil"
 )
 
 var metricsKeyMeshRootCAExpiry = []string{"mesh", "active-root-ca", "expiry"}
@@ -28,10 +29,14 @@ var CertExpirationGauges = []prometheus.GaugeDefinition{
 		Name: metricsKeyMeshActiveSigningCAExpiry,
 		Help: "Seconds until the service mesh signing certificate expires. Updated every hour",
 	},
+	{
+		Name: metricsKeyAgentTLSCertExpiry,
+		Help: "Seconds until the agent tls certificate expires. Updated every hour",
+	},
 }
 
-func rootCAExpiryMonitor(s *Server) certExpirationMonitor {
+func rootCAExpiryMonitor(s *Server) CertExpirationMonitor {
-	return certExpirationMonitor{
+	return CertExpirationMonitor{
 		Key: metricsKeyMeshRootCAExpiry,
 		Labels: []metrics.Label{
 			{Name: "datacenter", Value: s.config.Datacenter},
@@ -56,10 +61,10 @@ func getRootCAExpiry(s *Server) (time.Duration, error) {
 	return time.Until(root.NotAfter), nil
 }
 
-func signingCAExpiryMonitor(s *Server) certExpirationMonitor {
+func signingCAExpiryMonitor(s *Server) CertExpirationMonitor {
 	isPrimary := s.config.Datacenter == s.config.PrimaryDatacenter
 	if isPrimary {
-		return certExpirationMonitor{
+		return CertExpirationMonitor{
 			Key: metricsKeyMeshActiveSigningCAExpiry,
 			Labels: []metrics.Label{
 				{Name: "datacenter", Value: s.config.Datacenter},
@@ -76,17 +81,17 @@ func signingCAExpiryMonitor(s *Server) certExpirationMonitor {
 
 			},
 		}
-	} else {
+	}
-		return certExpirationMonitor{
+
-			Key: metricsKeyMeshActiveSigningCAExpiry,
+	return CertExpirationMonitor{
-			Labels: []metrics.Label{
+		Key: metricsKeyMeshActiveSigningCAExpiry,
-				{Name: "datacenter", Value: s.config.Datacenter},
+		Labels: []metrics.Label{
-			},
+			{Name: "datacenter", Value: s.config.Datacenter},
-			Logger: s.logger.Named(logging.Connect),
+		},
-			Query: func() (time.Duration, error) {
+		Logger: s.logger.Named(logging.Connect),
-				return getActiveIntermediateExpiry(s)
+		Query: func() (time.Duration, error) {
-			},
+			return getActiveIntermediateExpiry(s)
-		}
+		},
 	}
 }
 
@@ -109,7 +114,7 @@ func getActiveIntermediateExpiry(s *Server) (time.Duration, error) {
 	return time.Until(cert.NotAfter), nil
 }
 
-type certExpirationMonitor struct {
+type CertExpirationMonitor struct {
 	Key    []string
 	Labels []metrics.Label
 	Logger hclog.Logger
@@ -120,7 +125,7 @@ type certExpirationMonitor struct {
 
 const certExpirationMonitorInterval = time.Hour
 
-func (m certExpirationMonitor) monitor(ctx context.Context) error {
+func (m CertExpirationMonitor) Monitor(ctx context.Context) error {
 	ticker := time.NewTicker(certExpirationMonitorInterval)
 	defer ticker.Stop()
 
@@ -138,3 +143,30 @@ func (m certExpirationMonitor) monitor(ctx context.Context) error {
 		}
 	}
 }
+
+var metricsKeyAgentTLSCertExpiry = []string{"agent", "tls", "cert", "expiry"}
+
+// AgentTLSCertExpirationMonitor returns a CertExpirationMonitor which will
+// monitor the expiration of the certificate used for agent TLS.
+func AgentTLSCertExpirationMonitor(c *tlsutil.Configurator, logger hclog.Logger, dc string) CertExpirationMonitor {
+	return CertExpirationMonitor{
+		Key: metricsKeyAgentTLSCertExpiry,
+		Labels: []metrics.Label{
+			{Name: "node", Value: c.Base().NodeName},
+			{Name: "datacenter", Value: dc},
+		},
+		Logger: logger,
+		Query: func() (time.Duration, error) {
+			raw := c.Cert()
+			if raw == nil {
+				return 0, fmt.Errorf("tls not enabled")
+			}
+
+			cert, err := x509.ParseCertificate(raw.Certificate[0])
+			if err != nil {
+				return 0, fmt.Errorf("failed to parse agent tls cert: %w", err)
+			}
+			return time.Until(cert.NotAfter), nil
+		},
+	}
+}

website/content/docs/agent/telemetry.mdx

@@ -480,6 +480,7 @@ These metrics give insight into the health of the cluster as a whole.
 | `consul.catalog.connect.not-found.`   | Increments for each connect-based catalog query where the given service could not be found.                                                                                                                                                                                                                                                                                                                                               | queries                                 | counter |
 | `consul.mesh.active-root-ca.expiry`    | The number of seconds until the root CA expires, updated every hour. | seconds | gauge |
 | `consul.mesh.active-signing-ca.expiry` | The number of seconds until the signing CA expires, updated every hour.                                                                                                                                                                                                                                                                                                                                                            | seconds                                 | gauge   |
+| `consul.agent.tls.cert.expiry` | The number of seconds until the Agent TLS certificate expires, updated every hour.                                                                                                                                                                                                                                                                                                                                                            | seconds                                 | gauge   |
 
 ## Connect Built-in Proxy Metrics