Start the query frontend worker after the querier has been successfully initialized

Signed-off-by: Marco Pracucci <marco@pracucci.com>

Author: pracucci

pkg/cortex/modules.go

@@ -195,11 +195,6 @@ func (t *Cortex) stopDistributor() (err error) {
 }
 
 func (t *Cortex) initQuerier(cfg *Config) (err error) {
-	t.worker, err = frontend.NewWorker(cfg.Worker, httpgrpc_server.NewServer(t.server.HTTPServer.Handler), util.Logger)
-	if err != nil {
-		return
-	}
-
 	var store querier.ChunkStore
 
 	if cfg.Storage.Engine == storage.StorageEngineTSDB {
@@ -237,6 +232,13 @@ func (t *Cortex) initQuerier(cfg *Config) (err error) {
 	subrouter.Path("/chunks").Handler(t.httpAuthMiddleware.Wrap(querier.ChunksHandler(queryable)))
 	subrouter.Path("/user_stats").Handler(middleware.AuthenticateUser.Wrap(http.HandlerFunc(t.distributor.UserStatsHandler)))
 
+	// Start the query frontend worker once the query engine and the store
+	// have been successfully initialized.
+	t.worker, err = frontend.NewWorker(cfg.Worker, httpgrpc_server.NewServer(t.server.HTTPServer.Handler), util.Logger)
+	if err != nil {
+		return
+	}
+
 	// Once the execution reaches this point, all synchronous initialization has been
 	// done and the querier is ready to serve queries, so we're just returning a 202.
 	t.server.HTTP.Path("/ready").Handler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {