make sure there are CQs before acquiring lease

services/continuous_querier/service.go

@@ -192,11 +192,17 @@ func (s *Service) backgroundLoop() {
 			s.Logger.Println("continuous query service terminating")
 			return
 		case req := <-s.RunCh:
+			if !s.hasContinuousQueries() {
+				continue
+			}
 			if _, err := s.MetaClient.AcquireLease(leaseName); err == nil {
 				s.Logger.Printf("running continuous queries by request for time: %v", req.Now)
 				s.runContinuousQueries(req)
 			}
 		case <-time.After(s.RunInterval):
+			if !s.hasContinuousQueries() {
+				continue
+			}
 			if _, err := s.MetaClient.AcquireLease(leaseName); err == nil {
 				s.runContinuousQueries(&RunRequest{Now: time.Now()})
 			}
@@ -204,6 +210,23 @@ func (s *Service) backgroundLoop() {
 	}
 }
 
+// hasContinuousQueries returns true if any CQs exist.
+func (s *Service) hasContinuousQueries() bool {
+	// Get list of all databases.
+	dbs, err := s.MetaClient.Databases()
+	if err != nil {
+		s.Logger.Println("error getting databases")
+		return false
+	}
+	// Loop through all databases executing CQs.
+	for _, db := range dbs {
+		if len(db.ContinuousQueries) > 0 {
+			return true
+		}
+	}
+	return false
+}
+
 // runContinuousQueries gets CQs from the meta store and runs them.
 func (s *Service) runContinuousQueries(req *RunRequest) {
 	// Get list of all databases.