Rule manager: remove blocking channel in mail (#7631)

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

cmd/prometheus/main.go

@@ -660,18 +660,14 @@ func main() {
 	}
 	{
 		// Rule manager.
-		// TODO(krasi) refactor ruleManager.Run() to be blocking to avoid using an extra blocking channel.
-		cancel := make(chan struct{})
 		g.Add(
 			func() error {
 				<-reloadReady.C
 				ruleManager.Run()
-				<-cancel
 				return nil
 			},
 			func(err error) {
 				ruleManager.Stop()
-				close(cancel)
 			},
 		)
 	}

rules/manager.go

@@ -875,8 +875,13 @@ func NewManager(o *ManagerOptions) *Manager {
 	return m
 }
 
-// Run starts processing of the rule manager.
+// Run starts processing of the rule manager. It is blocking.
 func (m *Manager) Run() {
+	m.start()
+	<-m.done
+}
+
+func (m *Manager) start() {
 	close(m.block)
 }
 

rules/manager_test.go

@@ -716,7 +716,7 @@ func TestUpdate(t *testing.T) {
 		Context:    context.Background(),
 		Logger:     log.NewNopLogger(),
 	})
-	ruleManager.Run()
+	ruleManager.start()
 	defer ruleManager.Stop()
 
 	err := ruleManager.Update(10*time.Second, files, nil)
@@ -906,8 +906,8 @@ func TestMetricsUpdate(t *testing.T) {
 	}
 
 	storage := teststorage.New(t)
-	registry := prometheus.NewRegistry()
 	defer storage.Close()
+	registry := prometheus.NewRegistry()
 	opts := promql.EngineOpts{
 		Logger:     nil,
 		Reg:        nil,
@@ -923,7 +923,7 @@ func TestMetricsUpdate(t *testing.T) {
 		Logger:     log.NewNopLogger(),
 		Registerer: registry,
 	})
-	ruleManager.Run()
+	ruleManager.start()
 	defer ruleManager.Stop()
 
 	countMetrics := func() int {
@@ -997,7 +997,7 @@ func TestGroupStalenessOnRemoval(t *testing.T) {
 		Logger:     log.NewNopLogger(),
 	})
 	var stopped bool
-	ruleManager.Run()
+	ruleManager.start()
 	defer func() {
 		if !stopped {
 			ruleManager.Stop()
@@ -1074,7 +1074,7 @@ func TestMetricsStalenessOnManagerShutdown(t *testing.T) {
 		Logger:     log.NewNopLogger(),
 	})
 	var stopped bool
-	ruleManager.Run()
+	ruleManager.start()
 	defer func() {
 		if !stopped {
 			ruleManager.Stop()