Expose backend session limits through prometheus stats.

backend_configuration_stats_prometheus.go

@@ -26,6 +26,12 @@ import (
 )
 
 var (
+	statsBackendLimit = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: "signaling",
+		Subsystem: "backend",
+		Name:      "session_limit",
+		Help:      "The session limit of a backend",
+	}, []string{"backend"})
 	statsBackendLimitExceededTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
 		Namespace: "signaling",
 		Subsystem: "backend",
@@ -40,6 +46,7 @@ var (
 	})
 
 	backendConfigurationStats = []prometheus.Collector{
+		statsBackendLimit,
 		statsBackendLimitExceededTotal,
 		statsBackendsCurrent,
 	}
@@ -48,3 +55,15 @@ var (
 func RegisterBackendConfigurationStats() {
 	registerAll(backendConfigurationStats...)
 }
+
+func updateBackendStats(backend *Backend) {
+	if backend.sessionLimit > 0 {
+		statsBackendLimit.WithLabelValues(backend.id).Set(float64(backend.sessionLimit))
+	} else {
+		statsBackendLimit.DeleteLabelValues(backend.id)
+	}
+}
+
+func deleteBackendStats(backend *Backend) {
+	statsBackendLimit.DeleteLabelValues(backend.id)
+}

backend_storage_etcd.go

@@ -202,6 +202,7 @@ func (s *backendStorageEtcd) EtcdKeyUpdated(client *EtcdClient, key string, data
 		// Simple case, first backend for this host
 		log.Printf("Added backend %s (from %s)", info.Url, key)
 		s.backends[host] = []*Backend{backend}
+		updateBackendStats(backend)
 		statsBackendsCurrent.Inc()
 		s.wakeupForTesting()
 		return
@@ -212,6 +213,7 @@ func (s *backendStorageEtcd) EtcdKeyUpdated(client *EtcdClient, key string, data
 	for idx, entry := range entries {
 		if entry.id == key {
 			log.Printf("Updated backend %s (from %s)", info.Url, key)
+			updateBackendStats(backend)
 			entries[idx] = backend
 			replaced = true
 			break
@@ -222,6 +224,7 @@ func (s *backendStorageEtcd) EtcdKeyUpdated(client *EtcdClient, key string, data
 		// New backend, add to list.
 		log.Printf("Added backend %s (from %s)", info.Url, key)
 		s.backends[host] = append(entries, backend)
+		updateBackendStats(backend)
 		statsBackendsCurrent.Inc()
 	}
 	s.wakeupForTesting()
@@ -247,6 +250,7 @@ func (s *backendStorageEtcd) EtcdKeyDeleted(client *EtcdClient, key string, prev
 	newEntries := make([]*Backend, 0, len(entries)-1)
 	for _, entry := range entries {
 		if entry.id == key {
+			updateBackendStats(entry)
 			statsBackendsCurrent.Dec()
 			continue
 		}

backend_storage_static.go

@@ -64,12 +64,14 @@ func NewBackendStorageStatic(config *goconf.ConfigFile) (BackendStorage, error)
 		if sessionLimit > 0 {
 			log.Printf("Allow a maximum of %d sessions", sessionLimit)
 		}
+		updateBackendStats(compatBackend)
 		numBackends++
 	} else if backendIds, _ := config.GetString("backend", "backends"); backendIds != "" {
 		for host, configuredBackends := range getConfiguredHosts(backendIds, config, commonSecret) {
 			backends[host] = append(backends[host], configuredBackends...)
 			for _, be := range configuredBackends {
 				log.Printf("Backend %s added for %s", be.id, be.url)
+				updateBackendStats(be)
 			}
 			numBackends += len(configuredBackends)
 		}
@@ -111,6 +113,7 @@ func NewBackendStorageStatic(config *goconf.ConfigFile) (BackendStorage, error)
 			if sessionLimit > 0 {
 				log.Printf("Allow a maximum of %d sessions", sessionLimit)
 			}
+			updateBackendStats(compatBackend)
 			numBackends++
 		}
 	}
@@ -138,6 +141,7 @@ func (s *backendStorageStatic) RemoveBackendsForHost(host string) {
 	if oldBackends := s.backends[host]; len(oldBackends) > 0 {
 		for _, backend := range oldBackends {
 			log.Printf("Backend %s removed for %s", backend.id, backend.url)
+			deleteBackendStats(backend)
 		}
 		statsBackendsCurrent.Sub(float64(len(oldBackends)))
 	}
@@ -158,6 +162,7 @@ func (s *backendStorageStatic) UpsertHost(host string, backends []*Backend) {
 				s.backends[host][existingIndex] = newBackend
 				backends = append(backends[:index], backends[index+1:]...)
 				log.Printf("Backend %s updated for %s", newBackend.id, newBackend.url)
+				updateBackendStats(newBackend)
 				break
 			}
 			index++
@@ -166,13 +171,15 @@ func (s *backendStorageStatic) UpsertHost(host string, backends []*Backend) {
 			removed := s.backends[host][existingIndex]
 			log.Printf("Backend %s removed for %s", removed.id, removed.url)
 			s.backends[host] = append(s.backends[host][:existingIndex], s.backends[host][existingIndex+1:]...)
+			deleteBackendStats(removed)
 			statsBackendsCurrent.Dec()
 		}
 	}
 
 	s.backends[host] = append(s.backends[host], backends...)
 	for _, added := range backends {
 		log.Printf("Backend %s added for %s", added.id, added.url)
+		updateBackendStats(added)
 	}
 	statsBackendsCurrent.Add(float64(len(backends)))
 }

docs/prometheus-metrics.md

@@ -24,6 +24,7 @@ The following metrics are available:
 | `signaling_proxy_command_messages_total`          | Counter   | 0.4.0     | The total number of command messages                                      | `type`                            |
 | `signaling_proxy_payload_messages_total`          | Counter   | 0.4.0     | The total number of payload messages                                      | `type`                            |
 | `signaling_proxy_token_errors_total`              | Counter   | 0.4.0     | The total number of token errors                                          | `reason`                          |
+| `signaling_backend_session_limit`                 | Gauge     | 1.3.3     | The session limit of a backend (if set)                                   | `backend`                         |
 | `signaling_backend_session_limit_exceeded_total`  | Counter   | 0.4.0     | The number of times the session limit exceeded                            | `backend`                         |
 | `signaling_backend_current`                       | Gauge     | 0.4.0     | The current number of configured backends                                 |                                   |
 | `signaling_client_countries_total`                | Counter   | 0.4.0     | The total number of connections by country                                | `country`                         |