Add annotation for an agent metrics listener

agent-inject/agent/agent.go

@@ -131,6 +131,9 @@ type Agent struct {
 	// template_config specific configuration
 	VaultAgentTemplateConfig VaultAgentTemplateConfig
 
+	// VaultAgentMetricsListenerPort is the port used to server the Vault agent metrics
+	VaultAgentMetricsListenerPort uint16
+
 	// RunAsUser is the user ID to run the Vault agent container(s) as.
 	RunAsUser int64
 
@@ -544,6 +547,17 @@ func New(pod *corev1.Pod) (*Agent, error) {
 		return nil, err
 	}
 
+	if pod.Annotations[AnnotationAgentMetricsListenerPort] != "" {
+		vaultAgentMetricsListenerPort, err := parseutil.SafeParseInt(pod.Annotations[AnnotationAgentMetricsListenerPort])
+		if err != nil {
+			return agent, err
+		}
+		if vaultAgentMetricsListenerPort < 1 || vaultAgentMetricsListenerPort > 65535 {
+			return agent, errors.New("invalid port number: must be in the range 1 to 65535")
+		}
+		agent.VaultAgentMetricsListenerPort = uint16(vaultAgentMetricsListenerPort)
+	}
+
 	return agent, nil
 }
 

agent-inject/agent/annotations.go

@@ -323,6 +323,9 @@ const (
 	// should map to the same unique value provided in
 	// "vault.hashicorp.com/agent-inject-secret-". Defaults to false
 	AnnotationErrorOnMissingKey = "vault.hashicorp.com/error-on-missing-key"
+
+	// AnnotationAgentMetricsListenerPort configures the port the agent metrics server should listen on
+	AnnotationAgentMetricsListenerPort = "vault.hashicorp.com/agent-metrics-listener-port"
 )
 
 type AgentConfig struct {

agent-inject/agent/config.go

@@ -90,12 +90,13 @@ type Template struct {
 	ErrMissingKey  bool   `json:"error_on_missing_key,omitempty"`
 }
 
-// Listener defines the configuration for Vault Agent Cache Listener
+// Listener defines the configuration for Vault Agent Cache Listener and/ or Vault Agent Metrics Listener
 type Listener struct {
 	Type       string    `json:"type"`
 	Address    string    `json:"address"`
 	TLSDisable bool      `json:"tls_disable"`
 	AgentAPI   *AgentAPI `json:"agent_api,omitempty"`
+	Role       string    `json:"role,omitempty"`
 }
 
 // AgentAPI defines the agent_api stanza for a listener
@@ -271,7 +272,7 @@ func (a *Agent) newConfig(init bool) ([]byte, error) {
 
 	cacheListener := makeCacheListener(a.VaultAgentCache.ListenerPort)
 	if a.VaultAgentCache.Persist {
-		config.Listener = cacheListener
+		config.Listener = append(config.Listener, &cacheListener)
 		config.Cache = &Cache{
 			UseAutoAuthToken: a.VaultAgentCache.UseAutoAuthToken,
 			Persist: &CachePersist{
@@ -281,7 +282,7 @@ func (a *Agent) newConfig(init bool) ([]byte, error) {
 			},
 		}
 	} else if a.VaultAgentCache.Enable && !a.PrePopulateOnly && !init {
-		config.Listener = cacheListener
+		config.Listener = append(config.Listener, &cacheListener)
 		config.Cache = &Cache{
 			UseAutoAuthToken: a.VaultAgentCache.UseAutoAuthToken,
 		}
@@ -296,7 +297,7 @@ func (a *Agent) newConfig(init bool) ([]byte, error) {
 				EnableQuit: a.EnableQuit,
 			}
 		} else {
-			config.Listener = makeCacheListener(a.VaultAgentCache.ListenerPort)
+			config.Listener = append(config.Listener, &cacheListener)
 			config.Listener[0].AgentAPI = &AgentAPI{
 				EnableQuit: a.EnableQuit,
 			}
@@ -307,19 +308,31 @@ func (a *Agent) newConfig(init bool) ([]byte, error) {
 		}
 	}
 
+	if a.VaultAgentMetricsListenerPort > 0 {
+		metricsListener := makeMetricsListener(a.VaultAgentMetricsListenerPort)
+		config.Listener = append(config.Listener, &metricsListener)
+	}
+
 	return config.render()
 }
 
 func (c *Config) render() ([]byte, error) {
 	return json.Marshal(c)
 }
 
-func makeCacheListener(port string) []*Listener {
-	return []*Listener{
-		{
-			Type:       "tcp",
-			Address:    fmt.Sprintf("127.0.0.1:%s", port),
-			TLSDisable: true,
-		},
+func makeCacheListener(port string) Listener {
+	return Listener{
+		Type:       "tcp",
+		Address:    fmt.Sprintf("127.0.0.1:%s", port),
+		TLSDisable: true,
+	}
+}
+
+func makeMetricsListener(port uint16) Listener {
+	return Listener{
+		Type:       "tcp",
+		Address:    fmt.Sprintf("0.0.0.0:%d", port),
+		TLSDisable: true,
+		Role:       "metrics_only",
 	}
 }

agent-inject/agent/container_init_sidecar.go

@@ -95,6 +95,13 @@ func (a *Agent) ContainerInitSidecar() (corev1.Container, error) {
 	if a.SetSecurityContext {
 		newContainer.SecurityContext = a.securityContext()
 	}
+	if a.VaultAgentMetricsListenerPort > 0 {
+		containerPort := corev1.ContainerPort{
+			Name:          "agent-metrics",
+			ContainerPort: int32(a.VaultAgentMetricsListenerPort),
+		}
+		newContainer.Ports = append(newContainer.Ports, containerPort)
+	}
 
 	// apply any JSON patch requested
 	if a.InitJsonPatch == "" {

agent-inject/agent/container_sidecar.go

@@ -110,6 +110,13 @@ func (a *Agent) ContainerSidecar() (corev1.Container, error) {
 	if a.SetSecurityContext {
 		newContainer.SecurityContext = a.securityContext()
 	}
+	if a.VaultAgentMetricsListenerPort > 0 {
+		containerPort := corev1.ContainerPort{
+			Name:          "agent-metrics",
+			ContainerPort: int32(a.VaultAgentMetricsListenerPort),
+		}
+		newContainer.Ports = append(newContainer.Ports, containerPort)
+	}
 
 	// apply any JSON patch requested
 	if a.JsonPatch == "" {