Expose instance AZ in ring via Prometheus metric

Author: roystchiang

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## master / unreleased
 
 * [FEATURE] Ruler: Add `external_labels` option to tag all alerts with a given set of labels.
+* [ENHANCEMENT] Ring: Add `cortex_ring_availability_zone` metric to display which availability zone an instance is configured to run in. #4681
 
 ## 1.12.0 in pgoress
 

pkg/ring/basic_lifecycler.go

@@ -92,7 +92,7 @@ func NewBasicLifecycler(cfg BasicLifecyclerConfig, ringName, ringKey string, sto
 		logger:    logger,
 		store:     store,
 		delegate:  delegate,
-		metrics:   NewBasicLifecyclerMetrics(ringName, reg),
+		metrics:   NewBasicLifecyclerMetrics(ringName, cfg.Zone, reg),
 		actorChan: make(chan func()),
 	}
 

pkg/ring/basic_lifecycler_metrics.go

@@ -9,9 +9,16 @@ type BasicLifecyclerMetrics struct {
 	heartbeats  prometheus.Counter
 	tokensOwned prometheus.Gauge
 	tokensToOwn prometheus.Gauge
+	zoneInfo    prometheus.GaugeVec
 }
 
-func NewBasicLifecyclerMetrics(ringName string, reg prometheus.Registerer) *BasicLifecyclerMetrics {
+func NewBasicLifecyclerMetrics(ringName string, zone string, reg prometheus.Registerer) *BasicLifecyclerMetrics {
+	zoneInfo := promauto.With(reg).NewGaugeVec(prometheus.GaugeOpts{
+		Name: "ring_availability_zone",
+		Help: "The availability zone of the instance",
+	}, []string{"az"})
+	zoneInfo.WithLabelValues(zone).Set(1)
+
 	return &BasicLifecyclerMetrics{
 		heartbeats: promauto.With(reg).NewCounter(prometheus.CounterOpts{
 			Name:        "ring_member_heartbeats_total",
@@ -28,5 +35,6 @@ func NewBasicLifecyclerMetrics(ringName string, reg prometheus.Registerer) *Basi
 			Help:        "The number of tokens to own in the ring.",
 			ConstLabels: prometheus.Labels{"name": ringName},
 		}),
+		zoneInfo: *zoneInfo,
 	}
 }