Ruler: Add update label names routine for stateful ruler (thanos-io#6689

)

Signed-off-by: Saswata Mukherjee <saswataminsta@yahoo.com>

cmd/thanos/rule.go

@@ -642,6 +642,21 @@ func runRule(
 		)
 		storeServer := store.NewLimitedStoreServer(store.NewInstrumentedStoreServer(reg, tsdbStore), reg, conf.storeRateLimits)
 		options = append(options, grpcserver.WithServer(store.RegisterStoreServer(storeServer, logger)))
+
+		ctx, cancel := context.WithCancel(context.Background())
+		level.Debug(logger).Log("msg", "setting up periodic update for label names")
+		g.Add(func() error {
+			return runutil.Repeat(10*time.Second, ctx.Done(), func() error {
+				level.Debug(logger).Log("msg", "Starting label names update")
+
+				tsdbStore.UpdateLabelNames(ctx)
+
+				level.Debug(logger).Log("msg", "Finished label names update")
+				return nil
+			})
+		}, func(err error) {
+			cancel()
+		})
 	}
 
 	options = append(options, grpcserver.WithServer(