Fix duplicate alertmanager notifications

We need to wire up the notification log to gossip to share state
with peers.

Also avoid creating two throwaway metrics registries, since one will
do.

Signed-off-by: Bryan Boreham <[email protected]>

Author: bboreham

pkg/alertmanager/alertmanager.go

@@ -65,30 +65,31 @@ func New(cfg *Config) (*Alertmanager, error) {
 		stop:   make(chan struct{}),
 	}
 
+	// TODO(cortex): Build a registry that can merge metrics from multiple users.
+	// For now, these metrics are ignored, as we can't register the same
+	// metric twice with a single registry.
+	localRegistry := prometheus.NewRegistry()
+
 	am.wg.Add(1)
 	nflogID := fmt.Sprintf("nflog:%s", cfg.UserID)
 	var err error
 	am.nflog, err = nflog.New(
 		nflog.WithRetention(cfg.Retention),
 		nflog.WithSnapshot(filepath.Join(cfg.DataDir, nflogID)),
 		nflog.WithMaintenance(notificationLogMaintenancePeriod, am.stop, am.wg.Done),
-		// TODO(cortex): Build a registry that can merge metrics from multiple users.
-		// For now, these metrics are ignored, as we can't register the same
-		// metric twice with a single registry.
-		nflog.WithMetrics(prometheus.NewRegistry()),
+		nflog.WithMetrics(localRegistry),
 		nflog.WithLogger(log.With(am.logger, "component", "nflog")),
 	)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create notification log: %v", err)
 	}
+	if cfg.Peer != nil {
+		c := cfg.Peer.AddState("nfl:"+cfg.UserID, am.nflog, localRegistry)
+		am.nflog.SetBroadcast(c.Broadcast)
+	}
 
 	am.marker = types.NewMarker()
 
-	// TODO(cortex): Build a registry that can merge metrics from multiple users.
-	// For now, these metrics are ignored, as we can't register the same
-	// metric twice with a single registry.
-	localRegistry := prometheus.NewRegistry()
-
 	silencesID := fmt.Sprintf("silences:%s", cfg.UserID)
 	am.silences, err = silence.New(silence.Options{
 		SnapshotFile: filepath.Join(cfg.DataDir, silencesID),