diff --git a/retrieval/discovery/consul.go b/retrieval/discovery/consul.go
index fc2645a841..83310cd644 100644
--- a/retrieval/discovery/consul.go
+++ b/retrieval/discovery/consul.go
@@ -57,9 +57,8 @@ type ConsulDiscovery struct {
 	tagSeparator    string
 	scrapedServices map[string]struct{}
 
-	mu                sync.RWMutex
-	services          map[string]*consulService
-	runDone, srvsDone chan struct{}
+	mu       sync.RWMutex
+	services map[string]*consulService
 }
 
 // consulService contains data belonging to the same service.
@@ -93,8 +92,6 @@ func NewConsulDiscovery(conf *config.ConsulSDConfig) *ConsulDiscovery {
 		client:          client,
 		clientConf:      clientConf,
 		tagSeparator:    conf.TagSeparator,
-		runDone:         make(chan struct{}),
-		srvsDone:        make(chan struct{}, 1),
 		scrapedServices: map[string]struct{}{},
 		services:        map[string]*consulService{},
 	}
@@ -133,18 +130,22 @@ func (cd *ConsulDiscovery) Sources() []string {
 }
 
 // Run implements the TargetProvider interface.
-func (cd *ConsulDiscovery) Run(ch chan<- *config.TargetGroup) {
+func (cd *ConsulDiscovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	defer close(ch)
+	defer cd.stop()
 
 	update := make(chan *consulService, 10)
-	go cd.watchServices(update)
+	go cd.watchServices(update, done)
 
 	for {
 		select {
-		case <-cd.runDone:
+		case <-done:
 			return
 		case srv := <-update:
 			if srv.removed {
+				close(srv.done)
+
+				// Send clearing update.
 				ch <- &config.TargetGroup{Source: srv.name}
 				break
 			}
@@ -157,31 +158,20 @@ func (cd *ConsulDiscovery) Run(ch chan<- *config.TargetGroup) {
 	}
 }
 
-// Stop implements the TargetProvider interface.
-func (cd *ConsulDiscovery) Stop() {
-	log.Debugf("Stopping Consul service discovery for %s", cd.clientConf.Address)
-
+func (cd *ConsulDiscovery) stop() {
 	// The lock prevents Run from terminating while the watchers attempt
 	// to send on their channels.
 	cd.mu.Lock()
 	defer cd.mu.Unlock()
 
-	// The watching goroutines will terminate after their next watch timeout.
-	// As this can take long, the channel is buffered and we do not wait.
 	for _, srv := range cd.services {
-		srv.done <- struct{}{}
+		close(srv.done)
 	}
-	cd.srvsDone <- struct{}{}
-
-	// Terminate Run.
-	cd.runDone <- struct{}{}
-
-	log.Debugf("Consul service discovery for %s stopped.", cd.clientConf.Address)
 }
 
 // watchServices retrieves updates from Consul's services endpoint and sends
 // potential updates to the update channel.
-func (cd *ConsulDiscovery) watchServices(update chan<- *consulService) {
+func (cd *ConsulDiscovery) watchServices(update chan<- *consulService, done <-chan struct{}) {
 	var lastIndex uint64
 	for {
 		catalog := cd.client.Catalog()
@@ -191,8 +181,7 @@ func (cd *ConsulDiscovery) watchServices(update chan<- *consulService) {
 		})
 		if err != nil {
 			log.Errorf("Error refreshing service list: %s", err)
-			<-time.After(consulRetryInterval)
-			continue
+			time.Sleep(consulRetryInterval)
 		}
 		// If the index equals the previous one, the watch timed out with no update.
 		if meta.LastIndex == lastIndex {
@@ -202,7 +191,7 @@ func (cd *ConsulDiscovery) watchServices(update chan<- *consulService) {
 
 		cd.mu.Lock()
 		select {
-		case <-cd.srvsDone:
+		case <-done:
 			cd.mu.Unlock()
 			return
 		default:
@@ -218,7 +207,7 @@ func (cd *ConsulDiscovery) watchServices(update chan<- *consulService) {
 				srv = &consulService{
 					name:   name,
 					tgroup: &config.TargetGroup{},
-					done:   make(chan struct{}, 1),
+					done:   make(chan struct{}),
 				}
 				srv.tgroup.Source = name
 				cd.services[name] = srv
@@ -234,7 +223,6 @@ func (cd *ConsulDiscovery) watchServices(update chan<- *consulService) {
 			if _, ok := srvs[name]; !ok {
 				srv.removed = true
 				update <- srv
-				srv.done <- struct{}{}
 				delete(cd.services, name)
 			}
 		}
@@ -253,7 +241,7 @@ func (cd *ConsulDiscovery) watchService(srv *consulService, ch chan<- *config.Ta
 		})
 		if err != nil {
 			log.Errorf("Error refreshing service %s: %s", srv.name, err)
-			<-time.After(consulRetryInterval)
+			time.Sleep(consulRetryInterval)
 			continue
 		}
 		// If the index equals the previous one, the watch timed out with no update.
diff --git a/retrieval/discovery/dns.go b/retrieval/discovery/dns.go
index f171dd6da8..138cfaf524 100644
--- a/retrieval/discovery/dns.go
+++ b/retrieval/discovery/dns.go
@@ -64,11 +64,11 @@ func init() {
 type DNSDiscovery struct {
 	names []string
 
-	done   chan struct{}
-	ticker *time.Ticker
-	m      sync.RWMutex
-	port   int
-	qtype  uint16
+	done     chan struct{}
+	interval time.Duration
+	m        sync.RWMutex
+	port     int
+	qtype    uint16
 }
 
 // NewDNSDiscovery returns a new DNSDiscovery which periodically refreshes its targets.
@@ -83,41 +83,34 @@ func NewDNSDiscovery(conf *config.DNSSDConfig) *DNSDiscovery {
 		qtype = dns.TypeSRV
 	}
 	return &DNSDiscovery{
-		names:  conf.Names,
-		done:   make(chan struct{}),
-		ticker: time.NewTicker(time.Duration(conf.RefreshInterval)),
-		qtype:  qtype,
-		port:   conf.Port,
+		names:    conf.Names,
+		done:     make(chan struct{}),
+		interval: time.Duration(conf.RefreshInterval),
+		qtype:    qtype,
+		port:     conf.Port,
 	}
 }
 
 // Run implements the TargetProvider interface.
-func (dd *DNSDiscovery) Run(ch chan<- *config.TargetGroup) {
+func (dd *DNSDiscovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	defer close(ch)
 
+	ticker := time.NewTicker(dd.interval)
+	defer ticker.Stop()
+
 	// Get an initial set right away.
 	dd.refreshAll(ch)
 
 	for {
 		select {
-		case <-dd.ticker.C:
+		case <-ticker.C:
 			dd.refreshAll(ch)
-		case <-dd.done:
+		case <-done:
 			return
 		}
 	}
 }
 
-// Stop implements the TargetProvider interface.
-func (dd *DNSDiscovery) Stop() {
-	log.Debug("Stopping DNS discovery for %s...", dd.names)
-
-	dd.ticker.Stop()
-	dd.done <- struct{}{}
-
-	log.Debug("DNS discovery for %s stopped.", dd.names)
-}
-
 // Sources implements the TargetProvider interface.
 func (dd *DNSDiscovery) Sources() []string {
 	var srcs []string
diff --git a/retrieval/discovery/file.go b/retrieval/discovery/file.go
index 4c0655f031..b5839a87ec 100644
--- a/retrieval/discovery/file.go
+++ b/retrieval/discovery/file.go
@@ -39,7 +39,6 @@ type FileDiscovery struct {
 	paths    []string
 	watcher  *fsnotify.Watcher
 	interval time.Duration
-	done     chan struct{}
 
 	// lastRefresh stores which files were found during the last refresh
 	// and how many target groups they contained.
@@ -52,7 +51,6 @@ func NewFileDiscovery(conf *config.FileSDConfig) *FileDiscovery {
 	return &FileDiscovery{
 		paths:    conf.Names,
 		interval: time.Duration(conf.RefreshInterval),
-		done:     make(chan struct{}),
 	}
 }
 
@@ -106,8 +104,9 @@ func (fd *FileDiscovery) watchFiles() {
 }
 
 // Run implements the TargetProvider interface.
-func (fd *FileDiscovery) Run(ch chan<- *config.TargetGroup) {
+func (fd *FileDiscovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	defer close(ch)
+	defer fd.stop()
 
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
@@ -125,10 +124,13 @@ func (fd *FileDiscovery) Run(ch chan<- *config.TargetGroup) {
 		// Stopping has priority over refreshing. Thus we wrap the actual select
 		// clause to always catch done signals.
 		select {
-		case <-fd.done:
+		case <-done:
 			return
 		default:
 			select {
+			case <-done:
+				return
+
 			case event := <-fd.watcher.Events:
 				// fsnotify sometimes sends a bunch of events without name or operation.
 				// It's unclear what they are and why they are sent - filter them out.
@@ -154,9 +156,6 @@ func (fd *FileDiscovery) Run(ch chan<- *config.TargetGroup) {
 				if err != nil {
 					log.Errorf("Error on file watch: %s", err)
 				}
-
-			case <-fd.done:
-				return
 			}
 		}
 	}
@@ -198,11 +197,10 @@ func fileSource(filename string, i int) string {
 	return fmt.Sprintf("%s:%d", filename, i)
 }
 
-// Stop implements the TargetProvider interface.
-func (fd *FileDiscovery) Stop() {
+// stop shuts down the file watcher.
+func (fd *FileDiscovery) stop() {
 	log.Debugf("Stopping file discovery for %s...", fd.paths)
 
-	fd.done <- struct{}{}
 	// Closing the watcher will deadlock unless all events and errors are drained.
 	go func() {
 		for {
@@ -210,15 +208,13 @@ func (fd *FileDiscovery) Stop() {
 			case <-fd.watcher.Errors:
 			case <-fd.watcher.Events:
 				// Drain all events and errors.
-			case <-fd.done:
+			default:
 				return
 			}
 		}
 	}()
 	fd.watcher.Close()
 
-	fd.done <- struct{}{}
-
 	log.Debugf("File discovery for %s stopped.", fd.paths)
 }
 
diff --git a/retrieval/discovery/file_test.go b/retrieval/discovery/file_test.go
index 6d1f00c440..49e4fb175f 100644
--- a/retrieval/discovery/file_test.go
+++ b/retrieval/discovery/file_test.go
@@ -24,11 +24,13 @@ func testFileSD(t *testing.T, ext string) {
 	conf.Names = []string{"fixtures/_*" + ext}
 	conf.RefreshInterval = config.Duration(1 * time.Hour)
 
-	fsd := NewFileDiscovery(&conf)
-
-	ch := make(chan *config.TargetGroup)
-	go fsd.Run(ch)
-	defer fsd.Stop()
+	var (
+		fsd  = NewFileDiscovery(&conf)
+		ch   = make(chan *config.TargetGroup)
+		done = make(chan struct{})
+	)
+	go fsd.Run(ch, done)
+	defer close(done)
 
 	select {
 	case <-time.After(25 * time.Millisecond):
diff --git a/retrieval/discovery/marathon.go b/retrieval/discovery/marathon.go
index 5fc4d07a95..a057e96e1a 100644
--- a/retrieval/discovery/marathon.go
+++ b/retrieval/discovery/marathon.go
@@ -40,13 +40,12 @@ func (md *MarathonDiscovery) Sources() []string {
 }
 
 // Run implements the TargetProvider interface.
-func (md *MarathonDiscovery) Run(ch chan<- *config.TargetGroup) {
+func (md *MarathonDiscovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	defer close(ch)
 
 	for {
 		select {
-		case <-md.done:
-			log.Debug("Shutting down marathon discovery.")
+		case <-done:
 			return
 		case <-time.After(md.refreshInterval):
 			err := md.updateServices(ch)
@@ -57,11 +56,6 @@ func (md *MarathonDiscovery) Run(ch chan<- *config.TargetGroup) {
 	}
 }
 
-// Stop implements the TargetProvider interface.
-func (md *MarathonDiscovery) Stop() {
-	md.done <- struct{}{}
-}
-
 func (md *MarathonDiscovery) updateServices(ch chan<- *config.TargetGroup) error {
 	targetMap, err := md.fetchTargetGroups()
 	if err != nil {
diff --git a/retrieval/discovery/marathon_test.go b/retrieval/discovery/marathon_test.go
index fcf11562c6..3b681cf790 100644
--- a/retrieval/discovery/marathon_test.go
+++ b/retrieval/discovery/marathon_test.go
@@ -181,17 +181,18 @@ func TestMarathonSDRunAndStop(t *testing.T) {
 		return marathonTestAppList(marathonValidLabel, 1), nil
 	})
 	md.refreshInterval = time.Millisecond * 10
+	done := make(chan struct{})
 
 	go func() {
 		select {
 		case <-ch:
-			md.Stop()
+			close(done)
 		case <-time.After(md.refreshInterval * 3):
-			md.Stop()
+			close(done)
 			t.Fatalf("Update took too long.")
 		}
 	}()
-	md.Run(ch)
+	md.Run(ch, done)
 	select {
 	case <-ch:
 	default:
diff --git a/retrieval/discovery/serverset.go b/retrieval/discovery/serverset.go
index 5a84186fc6..b550989126 100644
--- a/retrieval/discovery/serverset.go
+++ b/retrieval/discovery/serverset.go
@@ -67,7 +67,6 @@ type ServersetDiscovery struct {
 	sources   map[string]*config.TargetGroup
 	sdUpdates *chan<- *config.TargetGroup
 	updates   chan zookeeperTreeCacheEvent
-	runDone   chan struct{}
 	treeCache *zookeeperTreeCache
 }
 
@@ -84,7 +83,6 @@ func NewServersetDiscovery(conf *config.ServersetSDConfig) *ServersetDiscovery {
 		conn:    conn,
 		updates: updates,
 		sources: map[string]*config.TargetGroup{},
-		runDone: make(chan struct{}),
 	}
 	go sd.processUpdates()
 	sd.treeCache = NewZookeeperTreeCache(conn, conf.Paths[0], updates)
@@ -132,7 +130,7 @@ func (sd *ServersetDiscovery) processUpdates() {
 }
 
 // Run implements the TargetProvider interface.
-func (sd *ServersetDiscovery) Run(ch chan<- *config.TargetGroup) {
+func (sd *ServersetDiscovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	// Send on everything we have seen so far.
 	sd.mu.Lock()
 	for _, targetGroup := range sd.sources {
@@ -142,20 +140,10 @@ func (sd *ServersetDiscovery) Run(ch chan<- *config.TargetGroup) {
 	sd.sdUpdates = &ch
 	sd.mu.Unlock()
 
-	<-sd.runDone
+	<-done
 	sd.treeCache.Stop()
 }
 
-// Stop implements the TargetProvider interface.
-func (sd *ServersetDiscovery) Stop() {
-	log.Debugf("Stopping serverset service discovery for %s %s", sd.conf.Servers, sd.conf.Paths)
-
-	// Terminate Run.
-	sd.runDone <- struct{}{}
-
-	log.Debugf("Serverset service discovery for %s %s stopped", sd.conf.Servers, sd.conf.Paths)
-}
-
 func parseServersetMember(data []byte, path string) (*clientmodel.LabelSet, error) {
 	member := serversetMember{}
 	err := json.Unmarshal(data, &member)
diff --git a/retrieval/helpers_test.go b/retrieval/helpers_test.go
index f72c93fe2c..f22cb5ab9a 100644
--- a/retrieval/helpers_test.go
+++ b/retrieval/helpers_test.go
@@ -53,17 +53,18 @@ type fakeTargetProvider struct {
 	update  chan *config.TargetGroup
 }
 
-func (tp *fakeTargetProvider) Run(ch chan<- *config.TargetGroup) {
+func (tp *fakeTargetProvider) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	defer close(ch)
-	for tg := range tp.update {
-		ch <- tg
+	for {
+		select {
+		case tg := <-tp.update:
+			ch <- tg
+		case <-done:
+			return
+		}
 	}
 }
 
-func (tp *fakeTargetProvider) Stop() {
-	close(tp.update)
-}
-
 func (tp *fakeTargetProvider) Sources() []string {
 	return tp.sources
 }
diff --git a/retrieval/targetmanager.go b/retrieval/targetmanager.go
index ba64f55e81..81984a7515 100644
--- a/retrieval/targetmanager.go
+++ b/retrieval/targetmanager.go
@@ -43,20 +43,19 @@ type TargetProvider interface {
 	// Run hands a channel to the target provider through which it can send
 	// updated target groups. The channel must be closed by the target provider
 	// if no more updates will be sent.
-	Run(chan<- *config.TargetGroup)
-	// Stop terminates any potential computation of the target provider. The
-	// channel received on Run must be closed afterwards.
-	Stop()
+	// On receiving from done Run must return.
+	Run(up chan<- *config.TargetGroup, done <-chan struct{})
 }
 
 // TargetManager maintains a set of targets, starts and stops their scraping and
 // creates the new targets based on the target groups it receives from various
 // target providers.
 type TargetManager struct {
-	m              sync.RWMutex
+	mtx            sync.RWMutex
 	globalLabels   clientmodel.LabelSet
 	sampleAppender storage.SampleAppender
 	running        bool
+	done           chan struct{}
 
 	// Targets by their source ID.
 	targets map[string][]*Target
@@ -73,31 +72,96 @@ func NewTargetManager(sampleAppender storage.SampleAppender) *TargetManager {
 	return tm
 }
 
+// merge multiple target group channels into a single output channel.
+func merge(done <-chan struct{}, cs ...<-chan targetGroupUpdate) <-chan targetGroupUpdate {
+	var wg sync.WaitGroup
+	out := make(chan targetGroupUpdate)
+
+	// Start an output goroutine for each input channel in cs.  output
+	// copies values from c to out until c or done is closed, then calls
+	// wg.Done.
+	redir := func(c <-chan targetGroupUpdate) {
+		defer wg.Done()
+		for n := range c {
+			select {
+			case out <- n:
+			case <-done:
+				return
+			}
+		}
+	}
+
+	wg.Add(len(cs))
+	for _, c := range cs {
+		go redir(c)
+	}
+
+	// Close the out channel if all inbound channels are closed.
+	go func() {
+		wg.Wait()
+		close(out)
+	}()
+	return out
+}
+
+// targetGroupUpdate is a potentially changed/new target group
+// for the given scrape configuration.
+type targetGroupUpdate struct {
+	tg   *config.TargetGroup
+	scfg *config.ScrapeConfig
+}
+
 // Run starts background processing to handle target updates.
 func (tm *TargetManager) Run() {
 	log.Info("Starting target manager...")
 
+	tm.done = make(chan struct{})
+
 	sources := map[string]struct{}{}
+	updates := []<-chan targetGroupUpdate{}
 
 	for scfg, provs := range tm.providers {
 		for _, prov := range provs {
-			ch := make(chan *config.TargetGroup)
-			go tm.handleTargetUpdates(scfg, ch)
-
+			// Get an initial set of available sources so we don't remove
+			// target groups from the last run that are still available.
 			for _, src := range prov.Sources() {
 				sources[src] = struct{}{}
 			}
 
+			tgc := make(chan *config.TargetGroup)
 			// Run the target provider after cleanup of the stale targets is done.
-			defer func(p TargetProvider, c chan *config.TargetGroup) {
-				go p.Run(c)
-			}(prov, ch)
+			defer func(prov TargetProvider, tgc chan *config.TargetGroup) {
+				go prov.Run(tgc, tm.done)
+			}(prov, tgc)
+
+			tgupc := make(chan targetGroupUpdate)
+			updates = append(updates, tgupc)
+
+			go func(scfg *config.ScrapeConfig) {
+				defer close(tgupc)
+				for {
+					select {
+					case tg := <-tgc:
+						if tg == nil {
+							break
+						}
+						tgupc <- targetGroupUpdate{tg: tg, scfg: scfg}
+					case <-tm.done:
+						return
+					}
+				}
+			}(scfg)
 		}
 	}
 
-	tm.m.Lock()
-	defer tm.m.Unlock()
+	// Merge all channels of incoming target group updates into a single
+	// one and keep applying the updates.
+	go tm.handleUpdates(merge(tm.done, updates...), tm.done)
 
+	tm.mtx.Lock()
+	defer tm.mtx.Unlock()
+
+	// Remove old target groups that are no longer in the set of sources.
 	tm.removeTargets(func(src string) bool {
 		if _, ok := sources[src]; ok {
 			return false
@@ -110,24 +174,32 @@ func (tm *TargetManager) Run() {
 
 // handleTargetUpdates receives target group updates and handles them in the
 // context of the given job config.
-func (tm *TargetManager) handleTargetUpdates(cfg *config.ScrapeConfig, ch <-chan *config.TargetGroup) {
-	for tg := range ch {
-		log.Debugf("Received potential update for target group %q", tg.Source)
+func (tm *TargetManager) handleUpdates(ch <-chan targetGroupUpdate, done <-chan struct{}) {
+	for {
+		select {
+		case update := <-ch:
+			if update.tg == nil {
+				break
+			}
+			log.Debugf("Received potential update for target group %q", update.tg.Source)
 
-		if err := tm.updateTargetGroup(tg, cfg); err != nil {
-			log.Errorf("Error updating targets: %s", err)
+			if err := tm.updateTargetGroup(update.tg, update.scfg); err != nil {
+				log.Errorf("Error updating targets: %s", err)
+			}
+		case <-done:
+			return
 		}
 	}
 }
 
 // Stop all background processing.
 func (tm *TargetManager) Stop() {
-	tm.m.RLock()
+	tm.mtx.RLock()
 	if tm.running {
 		defer tm.stop(true)
 	}
 	// Return the lock before calling tm.stop().
-	defer tm.m.RUnlock()
+	defer tm.mtx.RUnlock()
 }
 
 // stop background processing of the target manager. If removeTargets is true,
@@ -136,25 +208,10 @@ func (tm *TargetManager) stop(removeTargets bool) {
 	log.Info("Stopping target manager...")
 	defer log.Info("Target manager stopped.")
 
-	tm.m.Lock()
-	provs := []TargetProvider{}
-	for _, ps := range tm.providers {
-		provs = append(provs, ps...)
-	}
-	tm.m.Unlock()
+	close(tm.done)
 
-	var wg sync.WaitGroup
-	wg.Add(len(provs))
-	for _, prov := range provs {
-		go func(p TargetProvider) {
-			p.Stop()
-			wg.Done()
-		}(prov)
-	}
-	wg.Wait()
-
-	tm.m.Lock()
-	defer tm.m.Unlock()
+	tm.mtx.Lock()
+	defer tm.mtx.Unlock()
 
 	if removeTargets {
 		tm.removeTargets(nil)
@@ -194,8 +251,8 @@ func (tm *TargetManager) updateTargetGroup(tgroup *config.TargetGroup, cfg *conf
 		return err
 	}
 
-	tm.m.Lock()
-	defer tm.m.Unlock()
+	tm.mtx.Lock()
+	defer tm.mtx.Unlock()
 
 	if !tm.running {
 		return nil
@@ -261,8 +318,8 @@ func (tm *TargetManager) updateTargetGroup(tgroup *config.TargetGroup, cfg *conf
 
 // Pools returns the targets currently being scraped bucketed by their job name.
 func (tm *TargetManager) Pools() map[string][]*Target {
-	tm.m.RLock()
-	defer tm.m.RUnlock()
+	tm.mtx.RLock()
+	defer tm.mtx.RUnlock()
 
 	pools := map[string][]*Target{}
 
@@ -279,9 +336,9 @@ func (tm *TargetManager) Pools() map[string][]*Target {
 // by the new cfg. The state of targets that are valid in the new configuration remains unchanged.
 // Returns true on success.
 func (tm *TargetManager) ApplyConfig(cfg *config.Config) bool {
-	tm.m.RLock()
+	tm.mtx.RLock()
 	running := tm.running
-	tm.m.RUnlock()
+	tm.mtx.RUnlock()
 
 	if running {
 		tm.stop(false)
@@ -294,8 +351,8 @@ func (tm *TargetManager) ApplyConfig(cfg *config.Config) bool {
 		providers[scfg] = providersFromConfig(scfg)
 	}
 
-	tm.m.Lock()
-	defer tm.m.Unlock()
+	tm.mtx.Lock()
+	defer tm.mtx.Unlock()
 
 	tm.globalLabels = cfg.GlobalConfig.Labels
 	tm.providers = providers
@@ -325,15 +382,23 @@ func (tp *prefixedTargetProvider) Sources() []string {
 	return srcs
 }
 
-func (tp *prefixedTargetProvider) Run(ch chan<- *config.TargetGroup) {
+func (tp *prefixedTargetProvider) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
 	defer close(ch)
 
 	ch2 := make(chan *config.TargetGroup)
-	go tp.TargetProvider.Run(ch2)
+	go tp.TargetProvider.Run(ch2, done)
 
-	for tg := range ch2 {
-		tg.Source = tp.prefix(tg.Source)
-		ch <- tg
+	for {
+		select {
+		case <-done:
+			return
+		case tg := <-ch2:
+			if tg == nil {
+				break
+			}
+			tg.Source = tp.prefix(tg.Source)
+			ch <- tg
+		}
 	}
 }
 
@@ -382,8 +447,8 @@ func providersFromConfig(cfg *config.ScrapeConfig) []TargetProvider {
 
 // targetsFromGroup builds targets based on the given TargetGroup and config.
 func (tm *TargetManager) targetsFromGroup(tg *config.TargetGroup, cfg *config.ScrapeConfig) ([]*Target, error) {
-	tm.m.RLock()
-	defer tm.m.RUnlock()
+	tm.mtx.RLock()
+	defer tm.mtx.RUnlock()
 
 	targets := make([]*Target, 0, len(tg.Targets))
 	for i, labels := range tg.Targets {
@@ -470,15 +535,17 @@ func NewStaticProvider(groups []*config.TargetGroup) *StaticProvider {
 }
 
 // Run implements the TargetProvider interface.
-func (sd *StaticProvider) Run(ch chan<- *config.TargetGroup) {
-	for _, tg := range sd.TargetGroups {
-		ch <- tg
-	}
-	close(ch) // This provider never sends any updates.
-}
+func (sd *StaticProvider) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
+	defer close(ch)
 
-// Stop implements the TargetProvider interface.
-func (sd *StaticProvider) Stop() {}
+	for _, tg := range sd.TargetGroups {
+		select {
+		case <-done:
+			return
+		case ch <- tg:
+		}
+	}
+}
 
 // TargetGroups returns the provider's target groups.
 func (sd *StaticProvider) Sources() (srcs []string) {
diff --git a/retrieval/targetmanager_test.go b/retrieval/targetmanager_test.go
index a911ce8df7..8d9f3dc407 100644
--- a/retrieval/targetmanager_test.go
+++ b/retrieval/targetmanager_test.go
@@ -54,7 +54,10 @@ func TestPrefixedTargetProvider(t *testing.T) {
 	}
 
 	ch := make(chan *config.TargetGroup)
-	go tp.Run(ch)
+	done := make(chan struct{})
+
+	defer close(done)
+	go tp.Run(ch, done)
 
 	expGroup1 := *targetGroups[0]
 	expGroup2 := *targetGroups[1]
@@ -347,10 +350,10 @@ func TestTargetManagerConfigUpdate(t *testing.T) {
 		conf.ScrapeConfigs = step.scrapeConfigs
 		targetManager.ApplyConfig(conf)
 
-		<-time.After(1 * time.Millisecond)
+		time.Sleep(50 * time.Millisecond)
 
 		if len(targetManager.targets) != len(step.expected) {
-			t.Fatalf("step %d: sources mismatch %v, %v", targetManager.targets, step.expected)
+			t.Fatalf("step %d: sources mismatch: expected %v, got %v", i, step.expected, targetManager.targets)
 		}
 
 		for source, actTargets := range targetManager.targets {