chore: use channel to block until reader init

pkg/query-service/app/clickhouseReader/reader.go

@@ -144,7 +144,7 @@ func NewReader(localDB *sqlx.DB, configFile string) *ClickHouseReader {
 	}
 }
 
-func (r *ClickHouseReader) Start() {
+func (r *ClickHouseReader) Start(readerReady chan bool) {
 	logLevel := promlog.AllowedLevel{}
 	logLevel.Set("debug")
 	// allowedFormat := promlog.AllowedFormat{}
@@ -313,6 +313,7 @@ func (r *ClickHouseReader) Start() {
 	r.queryEngine = queryEngine
 	r.remoteStorage = remoteStorage
 	r.fanoutStorage = &fanoutStorage
+	readerReady <- true
 
 	if err := g.Run(); err != nil {
 		level.Error(logger).Log("err", err)

pkg/query-service/app/server.go

@@ -77,18 +77,20 @@ func NewServer(serverOptions *ServerOptions) (*Server, error) {
 	}
 
 	localDB.SetMaxOpenConns(10)
+	readerReady := make(chan bool)
 
 	var reader interfaces.Reader
 	storage := os.Getenv("STORAGE")
 	if storage == "clickhouse" {
 		zap.S().Info("Using ClickHouse as datastore ...")
 		clickhouseReader := clickhouseReader.NewReader(localDB, serverOptions.PromConfigPath)
-		go clickhouseReader.Start()
+		go clickhouseReader.Start(readerReady)
 		reader = clickhouseReader
 	} else {
 		return nil, fmt.Errorf("Storage type: %s is not supported in query service", storage)
 	}
 
+	<-readerReady
 	rm, err := makeRulesManager(serverOptions.PromConfigPath, constants.GetAlertManagerApiPrefix(), serverOptions.RuleRepoURL, localDB, reader, serverOptions.DisableRules)
 	if err != nil {
 		return nil, err

pkg/query-service/pqlEngine/engine.go

@@ -32,9 +32,6 @@ func FromConfigPath(promConfigPath string) (*PqlEngine, error) {
 }
 
 func FromReader(ch interfaces.Reader) (*PqlEngine, error) {
-	for ch.GetFanoutStorage() == nil {
-		time.Sleep(1 * time.Second)
-	}
 	return &PqlEngine{
 		engine:        ch.GetQueryEngine(),
 		fanoutStorage: *ch.GetFanoutStorage(),