remove dicovery race for the context field

cmd/prometheus/main.go

@@ -239,8 +239,13 @@ func main() {
 		ctxRule           = context.Background()
 
 		notifier = notifier.New(&cfg.notifier, log.With(logger, "component", "notifier"))
-		discoveryManagerScrape = discovery.NewManager(log.With(logger, "component", "discovery manager scrape"))
-		discoveryManagerNotify = discovery.NewManager(log.With(logger, "component", "discovery manager notify"))
+
+		ctxScrape, cancelScrape = context.WithCancel(context.Background())
+		discoveryManagerScrape  = discovery.NewManager(ctxScrape, log.With(logger, "component", "discovery manager scrape"))
+
+		ctxNotify, cancelNotify = context.WithCancel(context.Background())
+		discoveryManagerNotify  = discovery.NewManager(ctxNotify, log.With(logger, "component", "discovery manager notify"))
+
 		scrapeManager = retrieval.NewScrapeManager(log.With(logger, "component", "scrape manager"), fanoutStorage)
 		queryEngine   = promql.NewEngine(fanoutStorage, &cfg.queryEngine)
 		ruleManager   = rules.NewManager(&rules.ManagerOptions{
@@ -375,30 +380,28 @@ func main() {
 		)
 	}
 	{
-		ctx, cancel := context.WithCancel(context.Background())
 		g.Add(
 			func() error {
-				err := discoveryManagerScrape.Run(ctx)
+				err := discoveryManagerScrape.Run()
 				level.Info(logger).Log("msg", "Scrape discovery manager stopped")
 				return err
 			},
 			func(err error) {
 				level.Info(logger).Log("msg", "Stopping scrape discovery manager...")
-				cancel()
+				cancelScrape()
 			},
 		)
 	}
 	{
-		ctx, cancel := context.WithCancel(context.Background())
 		g.Add(
 			func() error {
-				err := discoveryManagerNotify.Run(ctx)
+				err := discoveryManagerNotify.Run()
 				level.Info(logger).Log("msg", "Notify discovery manager stopped")
 				return err
 			},
 			func(err error) {
 				level.Info(logger).Log("msg", "Stopping notify discovery manager...")
-				cancel()
+				cancelNotify()
 			},
 		)
 	}

discovery/manager.go

@@ -60,13 +60,13 @@ type poolKey struct {
 }
 
 // NewManager is the Discovery Manager constructor
-func NewManager(logger log.Logger) *Manager {
+func NewManager(ctx context.Context, logger log.Logger) *Manager {
 	return &Manager{
 		logger:         logger,
 		syncCh:         make(chan map[string][]*targetgroup.Group),
 		targets:        make(map[poolKey]map[string]*targetgroup.Group),
 		discoverCancel: []context.CancelFunc{},
-		ctx:            context.Background(),
+		ctx:            ctx,
 	}
 }
 
@@ -89,13 +89,12 @@ type Manager struct {
 }
 
 // Run starts the background processing
-func (m *Manager) Run(ctx context.Context) error {
-	m.ctx = ctx
+func (m *Manager) Run() error {
 	for {
 		select {
-		case <-ctx.Done():
+		case <-m.ctx.Done():
 			m.cancelDiscoverers()
-			return ctx.Err()
+			return m.ctx.Err()
 		}
 	}
 }