lib/promscrape/discovery/kubernetes: remove a mutex at urlWatcher - use groupWatcher mutex for accessing all the urlWatcher children

This simplifies the code a bit and reduces the probability of improper mutex handling and deadlocks.

lib/promscrape/discovery/kubernetes/api_watcher.go

@@ -33,6 +33,8 @@ type WatchEvent struct {
 // object is any Kubernetes object.
 type object interface {
 	key() string
+
+	// getTargetLabels must be called under gw.mu lock.
 	getTargetLabels(gw *groupWatcher) []map[string]string
 }
 
@@ -231,62 +233,13 @@ var (
 	})
 )
 
-// getObjectByRole returns an object with the given (namespace, name) key and the given role.
-func (gw *groupWatcher) getObjectByRole(role, namespace, name string) object {
+func (gw *groupWatcher) getObjectByRoleLocked(role, namespace, name string) object {
 	if gw == nil {
 		// this is needed for testing
 		return nil
 	}
-	o := gw.getCachedObjectByRole(role, namespace, name)
-	if o != nil {
-		// Fast path: the object has been found in the cache.
-		return o
-	}
-
-	// The object wasn't found in the cache. Try querying it directly from API server.
-	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1182#issuecomment-813353359 for details.
-	metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_direct_object_loads_total{role=%q}`, role)).Inc()
-	objectType := getObjectTypeByRole(role)
-	path := getAPIPath(objectType, namespace, "")
-	path += "/" + name
-	requestURL := gw.apiServer + path
-	resp, err := gw.doRequest(requestURL)
-	if err != nil {
-		metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_direct_object_load_errors_total{role=%q}`, role)).Inc()
-		logger.Errorf("cannot obtain data for object %s (namespace=%q, name=%q): %s", role, namespace, name, err)
-		return nil
-	}
-	data, err := ioutil.ReadAll(resp.Body)
-	_ = resp.Body.Close()
-	if err != nil {
-		metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_direct_object_load_errors_total{role=%q}`, role)).Inc()
-		logger.Errorf("cannot read response from %q: %s", requestURL, err)
-		return nil
-	}
-	if resp.StatusCode != http.StatusOK {
-		if resp.StatusCode == http.StatusNotFound {
-			metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_direct_object_load_misses_total{role=%q}`, role)).Inc()
-			return nil
-		}
-		metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_direct_object_load_errors_total{role=%q}`, role)).Inc()
-		logger.Errorf("unexpected status code when reading response from %q; got %d; want %d; response body: %q", requestURL, resp.StatusCode, http.StatusOK, data)
-		return nil
-	}
-	parseObject, _ := getObjectParsersForRole(role)
-	o, err = parseObject(data)
-	if err != nil {
-		metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_direct_object_load_errors_total{role=%q}`, role)).Inc()
-		logger.Errorf("cannot parse object obtained from %q: %s; response body: %q", requestURL, err, data)
-		return nil
-	}
-	// There is no need in storing the object in urlWatcher cache, since it should be eventually populated there by urlWatcher itself.
-	return o
-}
-
-func (gw *groupWatcher) getCachedObjectByRole(role, namespace, name string) object {
 	key := namespace + "/" + name
-	uws := gw.getURLWatchers()
-	for _, uw := range uws {
+	for _, uw := range gw.m {
 		if uw.role != role {
 			// Role mismatch
 			continue
@@ -295,26 +248,26 @@ func (gw *groupWatcher) getCachedObjectByRole(role, namespace, name string) obje
 			// Namespace mismatch
 			continue
 		}
-		uw.mu.Lock()
-		o := uw.objectsByKey[key]
-		uw.mu.Unlock()
-		if o != nil {
+		if o := uw.objectsByKey[key]; o != nil {
 			return o
 		}
 	}
 	return nil
 }
 
-func (gw *groupWatcher) refreshEndpointsLabels(namespace, key string) {
+func (gw *groupWatcher) refreshEndpointsLabelsLocked(namespace, key string) {
 	// Refresh endpoints and endpointslices labels for the corresponding service as Prometheus does.
 	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1240
-	gw.refreshObjectLabels("endpoints", namespace, key)
-	gw.refreshObjectLabels("endpointslices", namespace, key)
+	gw.refreshObjectLabelsLocked("endpoints", namespace, key)
+	gw.refreshObjectLabelsLocked("endpointslices", namespace, key)
 }
 
-func (gw *groupWatcher) refreshObjectLabels(role, namespace, key string) {
-	uws := gw.getURLWatchers()
-	for _, uw := range uws {
+func (gw *groupWatcher) refreshObjectLabelsLocked(role, namespace, key string) {
+	for _, uw := range gw.m {
+		if len(uw.aws) == 0 {
+			// No apiWatchers to notify
+			continue
+		}
 		if uw.role != role {
 			// Role mismatch
 			continue
@@ -323,16 +276,9 @@ func (gw *groupWatcher) refreshObjectLabels(role, namespace, key string) {
 			// Namespace mismatch
 			continue
 		}
-		var aws []*apiWatcher
-		uw.mu.Lock()
-		o := uw.objectsByKey[key]
-		if o != nil {
-			aws = uw.getAPIWatchersLocked()
-		}
-		uw.mu.Unlock()
-		if len(aws) > 0 {
+		if o := uw.objectsByKey[key]; o != nil {
 			labels := o.getTargetLabels(gw)
-			for _, aw := range aws {
+			for aw := range uw.aws {
 				aw.setScrapeWorks(namespace, key, labels)
 			}
 		}
@@ -350,14 +296,14 @@ func (gw *groupWatcher) startWatchersForRole(role string, aw *apiWatcher) {
 			uw = newURLWatcher(role, namespaces[i], apiURL, gw)
 			gw.m[apiURL] = uw
 		}
+		if aw != nil {
+			uw.subscribeAPIWatcherLocked(aw)
+		}
 		gw.mu.Unlock()
 		if needStart {
 			uw.reloadObjects()
 			go uw.watchForUpdates()
 		}
-		if aw != nil {
-			uw.subscribeAPIWatcher(aw)
-		}
 	}
 }
 
@@ -374,30 +320,24 @@ func (gw *groupWatcher) doRequest(requestURL string) (*http.Response, error) {
 }
 
 func (gw *groupWatcher) registerPendingAPIWatchers() {
-	uws := gw.getURLWatchers()
-	for _, uw := range uws {
-		uw.registerPendingAPIWatchers()
-	}
-}
-
-func (gw *groupWatcher) getURLWatchers() []*urlWatcher {
 	gw.mu.Lock()
-	uws := make([]*urlWatcher, 0, len(gw.m))
+	defer gw.mu.Unlock()
 	for _, uw := range gw.m {
-		uws = append(uws, uw)
+		uw.registerPendingAPIWatchersLocked()
 	}
-	gw.mu.Unlock()
-	return uws
 }
 
 func (gw *groupWatcher) unsubscribeAPIWatcher(aw *apiWatcher) {
-	uws := gw.getURLWatchers()
-	for _, uw := range uws {
-		uw.unsubscribeAPIWatcher(aw)
+	gw.mu.Lock()
+	defer gw.mu.Unlock()
+	for _, uw := range gw.m {
+		uw.unsubscribeAPIWatcherLocked(aw)
 	}
 }
 
 // urlWatcher watches for an apiURL and updates object states in objectsByKey.
+//
+// urlWatcher fields must be accessed under gw.mu lock.
 type urlWatcher struct {
 	role      string
 	namespace string
@@ -407,14 +347,11 @@ type urlWatcher struct {
 	parseObject     parseObjectFunc
 	parseObjectList parseObjectListFunc
 
-	// mu protects aws, awsPending, objectsByKey and resourceVersion
-	mu sync.Mutex
-
 	// awsPending contains pending apiWatcher objects, which are registered in a batch.
 	// Batch registering saves CPU time needed for registering big number of Kubernetes objects
 	// shared among big number of scrape jobs, since per-object labels are generated only once
 	// for all the scrape jobs (each scrape job is associated with a single apiWatcher).
-	// See reloadScrapeWorksForAPIWatchers for details.
+	// See reloadScrapeWorksForAPIWatchersLocked for details.
 	awsPending map[*apiWatcher]struct{}
 
 	// aws contains registered apiWatcher objects
@@ -458,37 +395,31 @@ func newURLWatcher(role, namespace, apiURL string, gw *groupWatcher) *urlWatcher
 	return uw
 }
 
-func (uw *urlWatcher) subscribeAPIWatcher(aw *apiWatcher) {
-	uw.mu.Lock()
+func (uw *urlWatcher) subscribeAPIWatcherLocked(aw *apiWatcher) {
 	if _, ok := uw.aws[aw]; !ok {
 		if _, ok := uw.awsPending[aw]; !ok {
 			uw.awsPending[aw] = struct{}{}
 			metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_subscribers{role=%q,status="pending"}`, uw.role)).Inc()
 		}
 	}
-	uw.mu.Unlock()
 }
 
-func (uw *urlWatcher) registerPendingAPIWatchers() {
-	uw.mu.Lock()
+func (uw *urlWatcher) registerPendingAPIWatchersLocked() {
 	if len(uw.awsPending) == 0 {
-		uw.mu.Unlock()
 		return
 	}
 	awsPending := make([]*apiWatcher, 0, len(uw.awsPending))
 	for aw := range uw.awsPending {
 		awsPending = append(awsPending, aw)
-		delete(uw.awsPending, aw)
 		uw.aws[aw] = struct{}{}
 	}
-	uw.reloadScrapeWorksForAPIWatchers(awsPending, uw.objectsByKey)
-	uw.mu.Unlock()
+	uw.reloadScrapeWorksForAPIWatchersLocked(uw.awsPending)
+	uw.awsPending = make(map[*apiWatcher]struct{})
 	metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_subscribers{role=%q,status="working"}`, uw.role)).Add(len(awsPending))
 	metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_subscribers{role=%q,status="pending"}`, uw.role)).Add(-len(awsPending))
 }
 
-func (uw *urlWatcher) unsubscribeAPIWatcher(aw *apiWatcher) {
-	uw.mu.Lock()
+func (uw *urlWatcher) unsubscribeAPIWatcherLocked(aw *apiWatcher) {
 	if _, ok := uw.awsPending[aw]; ok {
 		delete(uw.awsPending, aw)
 		metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_subscribers{role=%q,status="pending"}`, uw.role)).Dec()
@@ -497,20 +428,19 @@ func (uw *urlWatcher) unsubscribeAPIWatcher(aw *apiWatcher) {
 		delete(uw.aws, aw)
 		metrics.GetOrCreateCounter(fmt.Sprintf(`vm_promscrape_discovery_kubernetes_subscribers{role=%q,status="working"}`, uw.role)).Dec()
 	}
-	uw.mu.Unlock()
 }
 
 func (uw *urlWatcher) setResourceVersion(resourceVersion string) {
-	uw.mu.Lock()
+	uw.gw.mu.Lock()
 	uw.resourceVersion = resourceVersion
-	uw.mu.Unlock()
+	uw.gw.mu.Unlock()
 }
 
 // reloadObjects reloads objects to the latest state and returns resourceVersion for the latest state.
 func (uw *urlWatcher) reloadObjects() string {
-	uw.mu.Lock()
+	uw.gw.mu.Lock()
 	resourceVersion := uw.resourceVersion
-	uw.mu.Unlock()
+	uw.gw.mu.Unlock()
 	if resourceVersion != "" {
 		// Fast path - there is no need in reloading the objects.
 		return resourceVersion
@@ -535,7 +465,7 @@ func (uw *urlWatcher) reloadObjects() string {
 		return ""
 	}
 
-	uw.mu.Lock()
+	uw.gw.mu.Lock()
 	var updated, removed, added int
 	for key := range uw.objectsByKey {
 		if o, ok := objectsByKey[key]; ok {
@@ -556,31 +486,34 @@ func (uw *urlWatcher) reloadObjects() string {
 	uw.objectsRemoved.Add(removed)
 	uw.objectsAdded.Add(added)
 	uw.objectsCount.Add(added - removed)
+	uw.reloadScrapeWorksForAPIWatchersLocked(uw.aws)
 	uw.resourceVersion = metadata.ResourceVersion
-	aws := uw.getAPIWatchersLocked()
-	uw.mu.Unlock()
-
-	uw.reloadScrapeWorksForAPIWatchers(aws, objectsByKey)
 	if uw.role == "service" {
 		// Refresh endpoints labels for the corresponding services as Prometheus does.
 		// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1240
 		for key := range objectsByKey {
-			uw.gw.refreshEndpointsLabels(uw.namespace, key)
+			uw.gw.refreshEndpointsLabelsLocked(uw.namespace, key)
 		}
 	}
+	uw.gw.mu.Unlock()
+
 	logger.Infof("reloaded %d objects from %q", len(objectsByKey), requestURL)
 	return uw.resourceVersion
 }
 
-func (uw *urlWatcher) reloadScrapeWorksForAPIWatchers(aws []*apiWatcher, objectsByKey map[string]object) {
-	if len(aws) == 0 {
+func (uw *urlWatcher) reloadScrapeWorksForAPIWatchersLocked(awsMap map[*apiWatcher]struct{}) {
+	if len(awsMap) == 0 {
 		return
 	}
+	aws := make([]*apiWatcher, 0, len(awsMap))
+	for aw := range awsMap {
+		aws = append(aws, aw)
+	}
 	swosByKey := make([]map[string][]interface{}, len(aws))
 	for i := range aws {
 		swosByKey[i] = make(map[string][]interface{})
 	}
-	for key, o := range objectsByKey {
+	for key, o := range uw.objectsByKey {
 		labels := o.getTargetLabels(uw.gw)
 		for i, aw := range aws {
 			swos := aw.getScrapeWorkObjectsForLabels(labels)
@@ -594,15 +527,6 @@ func (uw *urlWatcher) reloadScrapeWorksForAPIWatchers(aws []*apiWatcher, objects
 	}
 }
 
-func (uw *urlWatcher) getAPIWatchersLocked() []*apiWatcher {
-	awsMap := uw.aws
-	aws := make([]*apiWatcher, 0, len(awsMap))
-	for aw := range awsMap {
-		aws = append(aws, aw)
-	}
-	return aws
-}
-
 // watchForUpdates watches for object updates starting from uw.resourceVersion and updates the corresponding objects to the latest state.
 //
 // See https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes
@@ -678,7 +602,7 @@ func (uw *urlWatcher) readObjectUpdateStream(r io.Reader) error {
 				return err
 			}
 			key := o.key()
-			uw.mu.Lock()
+			uw.gw.mu.Lock()
 			if _, ok := uw.objectsByKey[key]; !ok {
 				uw.objectsCount.Inc()
 				uw.objectsAdded.Inc()
@@ -686,41 +610,39 @@ func (uw *urlWatcher) readObjectUpdateStream(r io.Reader) error {
 				uw.objectsUpdated.Inc()
 			}
 			uw.objectsByKey[key] = o
-			aws := uw.getAPIWatchersLocked()
-			uw.mu.Unlock()
-			if len(aws) > 0 {
+			if len(uw.aws) > 0 {
 				labels := o.getTargetLabels(uw.gw)
-				for _, aw := range aws {
+				for aw := range uw.aws {
 					aw.setScrapeWorks(uw.namespace, key, labels)
 				}
 			}
 			if uw.role == "service" {
 				// Refresh endpoints labels for the corresponding service as Prometheus does.
 				// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1240
-				uw.gw.refreshEndpointsLabels(uw.namespace, key)
+				uw.gw.refreshEndpointsLabelsLocked(uw.namespace, key)
 			}
+			uw.gw.mu.Unlock()
 		case "DELETED":
 			o, err := uw.parseObject(we.Object)
 			if err != nil {
 				return err
 			}
 			key := o.key()
-			uw.mu.Lock()
+			uw.gw.mu.Lock()
 			if _, ok := uw.objectsByKey[key]; ok {
 				uw.objectsCount.Dec()
 				uw.objectsRemoved.Inc()
 				delete(uw.objectsByKey, key)
 			}
-			aws := uw.getAPIWatchersLocked()
-			uw.mu.Unlock()
-			for _, aw := range aws {
+			for aw := range uw.aws {
 				aw.removeScrapeWorks(uw.namespace, key)
 			}
 			if uw.role == "service" {
 				// Refresh endpoints labels for the corresponding service as Prometheus does.
 				// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1240
-				uw.gw.refreshEndpointsLabels(uw.namespace, key)
+				uw.gw.refreshEndpointsLabelsLocked(uw.namespace, key)
 			}
+			uw.gw.mu.Unlock()
 		case "BOOKMARK":
 			// See https://kubernetes.io/docs/reference/using-api/api-concepts/#watch-bookmarks
 			bm, err := parseBookmark(we.Object)

lib/promscrape/discovery/kubernetes/endpoints.go

@@ -92,7 +92,7 @@ type EndpointPort struct {
 // See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#endpoints
 func (eps *Endpoints) getTargetLabels(gw *groupWatcher) []map[string]string {
 	var svc *Service
-	if o := gw.getObjectByRole("service", eps.Metadata.Namespace, eps.Metadata.Name); o != nil {
+	if o := gw.getObjectByRoleLocked("service", eps.Metadata.Namespace, eps.Metadata.Name); o != nil {
 		svc = o.(*Service)
 	}
 	podPortsSeen := make(map[*Pod][]int)
@@ -140,7 +140,7 @@ func appendEndpointLabelsForAddresses(ms []map[string]string, gw *groupWatcher,
 	for _, ea := range eas {
 		var p *Pod
 		if ea.TargetRef.Name != "" {
-			if o := gw.getObjectByRole("pod", ea.TargetRef.Namespace, ea.TargetRef.Name); o != nil {
+			if o := gw.getObjectByRoleLocked("pod", ea.TargetRef.Namespace, ea.TargetRef.Name); o != nil {
 				p = o.(*Pod)
 			}
 		}

lib/promscrape/discovery/kubernetes/endpointslices.go

@@ -39,14 +39,14 @@ func parseEndpointSlice(data []byte) (object, error) {
 // See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#endpointslices
 func (eps *EndpointSlice) getTargetLabels(gw *groupWatcher) []map[string]string {
 	var svc *Service
-	if o := gw.getObjectByRole("service", eps.Metadata.Namespace, eps.Metadata.Name); o != nil {
+	if o := gw.getObjectByRoleLocked("service", eps.Metadata.Namespace, eps.Metadata.Name); o != nil {
 		svc = o.(*Service)
 	}
 	podPortsSeen := make(map[*Pod][]int)
 	var ms []map[string]string
 	for _, ess := range eps.Endpoints {
 		var p *Pod
-		if o := gw.getObjectByRole("pod", ess.TargetRef.Namespace, ess.TargetRef.Name); o != nil {
+		if o := gw.getObjectByRoleLocked("pod", ess.TargetRef.Namespace, ess.TargetRef.Name); o != nil {
 			p = o.(*Pod)
 		}
 		for _, epp := range eps.Ports {