diff --git a/retrieval/discovery/consul.go b/retrieval/discovery/consul.go
index 84ed6d7ac1..5120081700 100644
--- a/retrieval/discovery/consul.go
+++ b/retrieval/discovery/consul.go
@@ -15,7 +15,6 @@ package discovery
 
 import (
 	"fmt"
-	"net/http"
 	"strconv"
 	"strings"
 	"sync"
@@ -24,6 +23,7 @@ import (
 	consul "github.com/hashicorp/consul/api"
 	"github.com/prometheus/common/log"
 	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
 )
@@ -113,52 +113,24 @@ func NewConsulDiscovery(conf *config.ConsulSDConfig) (*ConsulDiscovery, error) {
 	return cd, nil
 }
 
-// Sources implements the TargetProvider interface.
-func (cd *ConsulDiscovery) Sources() []string {
-	clientConf := *cd.clientConf
-	clientConf.HttpClient = &http.Client{Timeout: 5 * time.Second}
-
-	client, err := consul.NewClient(&clientConf)
-	if err != nil {
-		// NewClient always returns a nil error.
-		panic(fmt.Errorf("discovery.ConsulDiscovery.Sources: %s", err))
-	}
-
-	srvs, _, err := client.Catalog().Services(nil)
-	if err != nil {
-		log.Errorf("Error refreshing service list: %s", err)
-		return nil
-	}
-	cd.mu.Lock()
-	defer cd.mu.Unlock()
-
-	srcs := make([]string, 0, len(srvs))
-	for name := range srvs {
-		if _, ok := cd.scrapedServices[name]; len(cd.scrapedServices) == 0 || ok {
-			srcs = append(srcs, name)
-		}
-	}
-	return srcs
-}
-
 // Run implements the TargetProvider interface.
-func (cd *ConsulDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (cd *ConsulDiscovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	defer close(ch)
 	defer cd.stop()
 
 	update := make(chan *consulService, 10)
-	go cd.watchServices(update, done)
+	go cd.watchServices(update, ctx.Done())
 
 	for {
 		select {
-		case <-done:
+		case <-ctx.Done():
 			return
 		case srv := <-update:
 			if srv.removed {
 				close(srv.done)
 
 				// Send clearing update.
-				ch <- config.TargetGroup{Source: srv.name}
+				ch <- []*config.TargetGroup{{Source: srv.name}}
 				break
 			}
 			// Launch watcher for the service.
@@ -244,7 +216,7 @@ func (cd *ConsulDiscovery) watchServices(update chan<- *consulService, done <-ch
 
 // watchService retrieves updates about srv from Consul's service endpoint.
 // On a potential update the resulting target group is sent to ch.
-func (cd *ConsulDiscovery) watchService(srv *consulService, ch chan<- config.TargetGroup) {
+func (cd *ConsulDiscovery) watchService(srv *consulService, ch chan<- []*config.TargetGroup) {
 	catalog := cd.client.Catalog()
 	for {
 		nodes, meta, err := catalog.Service(srv.name, "", &consul.QueryOptions{
@@ -288,7 +260,11 @@ func (cd *ConsulDiscovery) watchService(srv *consulService, ch chan<- config.Tar
 		default:
 			// Continue.
 		}
-		ch <- srv.tgroup
+		// TODO(fabxc): do a copy for now to avoid races. The integration
+		// needs needs some general cleanup.
+		tg := srv.tgroup
+		ch <- []*config.TargetGroup{&tg}
+
 		cd.mu.Unlock()
 	}
 }
diff --git a/retrieval/discovery/dns.go b/retrieval/discovery/dns.go
index 40a8841e1f..3c75f07fc7 100644
--- a/retrieval/discovery/dns.go
+++ b/retrieval/discovery/dns.go
@@ -24,6 +24,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/log"
 	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
 )
@@ -91,7 +92,7 @@ func NewDNSDiscovery(conf *config.DNSSDConfig) *DNSDiscovery {
 }
 
 // Run implements the TargetProvider interface.
-func (dd *DNSDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (dd *DNSDiscovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	defer close(ch)
 
 	ticker := time.NewTicker(dd.interval)
@@ -104,22 +105,13 @@ func (dd *DNSDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{})
 		select {
 		case <-ticker.C:
 			dd.refreshAll(ch)
-		case <-done:
+		case <-ctx.Done():
 			return
 		}
 	}
 }
 
-// Sources implements the TargetProvider interface.
-func (dd *DNSDiscovery) Sources() []string {
-	var srcs []string
-	for _, name := range dd.names {
-		srcs = append(srcs, name)
-	}
-	return srcs
-}
-
-func (dd *DNSDiscovery) refreshAll(ch chan<- config.TargetGroup) {
+func (dd *DNSDiscovery) refreshAll(ch chan<- []*config.TargetGroup) {
 	var wg sync.WaitGroup
 	wg.Add(len(dd.names))
 	for _, name := range dd.names {
@@ -133,7 +125,7 @@ func (dd *DNSDiscovery) refreshAll(ch chan<- config.TargetGroup) {
 	wg.Wait()
 }
 
-func (dd *DNSDiscovery) refresh(name string, ch chan<- config.TargetGroup) error {
+func (dd *DNSDiscovery) refresh(name string, ch chan<- []*config.TargetGroup) error {
 	response, err := lookupAll(name, dd.qtype)
 	dnsSDLookupsCount.Inc()
 	if err != nil {
@@ -141,7 +133,8 @@ func (dd *DNSDiscovery) refresh(name string, ch chan<- config.TargetGroup) error
 		return err
 	}
 
-	var tg config.TargetGroup
+	tg := &config.TargetGroup{}
+
 	for _, record := range response.Answer {
 		target := model.LabelValue("")
 		switch addr := record.(type) {
@@ -166,7 +159,7 @@ func (dd *DNSDiscovery) refresh(name string, ch chan<- config.TargetGroup) error
 	}
 
 	tg.Source = name
-	ch <- tg
+	ch <- []*config.TargetGroup{tg}
 
 	return nil
 }
diff --git a/retrieval/discovery/ec2.go b/retrieval/discovery/ec2.go
index 46b3d371f4..e390169486 100644
--- a/retrieval/discovery/ec2.go
+++ b/retrieval/discovery/ec2.go
@@ -23,6 +23,7 @@ import (
 	"github.com/aws/aws-sdk-go/aws/defaults"
 	"github.com/prometheus/common/log"
 	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
 
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/prometheus/prometheus/config"
@@ -46,7 +47,6 @@ const (
 // the TargetProvider interface.
 type EC2Discovery struct {
 	aws      *aws.Config
-	done     chan struct{}
 	interval time.Duration
 	port     int
 }
@@ -62,14 +62,13 @@ func NewEC2Discovery(conf *config.EC2SDConfig) *EC2Discovery {
 			Region:      &conf.Region,
 			Credentials: creds,
 		},
-		done:     make(chan struct{}),
 		interval: time.Duration(conf.RefreshInterval),
 		port:     conf.Port,
 	}
 }
 
 // Run implements the TargetProvider interface.
-func (ed *EC2Discovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (ed *EC2Discovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	defer close(ch)
 
 	ticker := time.NewTicker(ed.interval)
@@ -80,7 +79,7 @@ func (ed *EC2Discovery) Run(ch chan<- config.TargetGroup, done <-chan struct{})
 	if err != nil {
 		log.Error(err)
 	} else {
-		ch <- *tg
+		ch <- []*config.TargetGroup{tg}
 	}
 
 	for {
@@ -90,19 +89,14 @@ func (ed *EC2Discovery) Run(ch chan<- config.TargetGroup, done <-chan struct{})
 			if err != nil {
 				log.Error(err)
 			} else {
-				ch <- *tg
+				ch <- []*config.TargetGroup{tg}
 			}
-		case <-done:
+		case <-ctx.Done():
 			return
 		}
 	}
 }
 
-// Sources implements the TargetProvider interface.
-func (ed *EC2Discovery) Sources() []string {
-	return []string{*ed.aws.Region}
-}
-
 func (ed *EC2Discovery) refresh() (*config.TargetGroup, error) {
 	ec2s := ec2.New(ed.aws)
 	tg := &config.TargetGroup{
diff --git a/retrieval/discovery/file.go b/retrieval/discovery/file.go
index eb0411b30f..9aedb16058 100644
--- a/retrieval/discovery/file.go
+++ b/retrieval/discovery/file.go
@@ -23,6 +23,7 @@ import (
 
 	"github.com/prometheus/common/log"
 	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
 	"gopkg.in/fsnotify.v1"
 	"gopkg.in/yaml.v2"
 
@@ -53,23 +54,6 @@ func NewFileDiscovery(conf *config.FileSDConfig) *FileDiscovery {
 	}
 }
 
-// Sources implements the TargetProvider interface.
-func (fd *FileDiscovery) Sources() []string {
-	var srcs []string
-	// As we allow multiple target groups per file we have no choice
-	// but to parse them all.
-	for _, p := range fd.listFiles() {
-		tgroups, err := readFile(p)
-		if err != nil {
-			log.Errorf("Error reading file %q: %s", p, err)
-		}
-		for _, tg := range tgroups {
-			srcs = append(srcs, tg.Source)
-		}
-	}
-	return srcs
-}
-
 // listFiles returns a list of all files that match the configured patterns.
 func (fd *FileDiscovery) listFiles() []string {
 	var paths []string
@@ -103,7 +87,7 @@ func (fd *FileDiscovery) watchFiles() {
 }
 
 // Run implements the TargetProvider interface.
-func (fd *FileDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (fd *FileDiscovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	defer close(ch)
 	defer fd.stop()
 
@@ -123,11 +107,11 @@ func (fd *FileDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{})
 		// Stopping has priority over refreshing. Thus we wrap the actual select
 		// clause to always catch done signals.
 		select {
-		case <-done:
+		case <-ctx.Done():
 			return
 		default:
 			select {
-			case <-done:
+			case <-ctx.Done():
 				return
 
 			case event := <-fd.watcher.Events:
@@ -188,7 +172,7 @@ func (fd *FileDiscovery) stop() {
 
 // refresh reads all files matching the discovery's patterns and sends the respective
 // updated target groups through the channel.
-func (fd *FileDiscovery) refresh(ch chan<- config.TargetGroup) {
+func (fd *FileDiscovery) refresh(ch chan<- []*config.TargetGroup) {
 	ref := map[string]int{}
 	for _, p := range fd.listFiles() {
 		tgroups, err := readFile(p)
@@ -198,9 +182,8 @@ func (fd *FileDiscovery) refresh(ch chan<- config.TargetGroup) {
 			ref[p] = fd.lastRefresh[p]
 			continue
 		}
-		for _, tg := range tgroups {
-			ch <- *tg
-		}
+		ch <- tgroups
+
 		ref[p] = len(tgroups)
 	}
 	// Send empty updates for sources that disappeared.
@@ -208,7 +191,9 @@ func (fd *FileDiscovery) refresh(ch chan<- config.TargetGroup) {
 		m, ok := ref[f]
 		if !ok || n > m {
 			for i := m; i < n; i++ {
-				ch <- config.TargetGroup{Source: fileSource(f, i)}
+				ch <- []*config.TargetGroup{
+					{Source: fileSource(f, i)},
+				}
 			}
 		}
 	}
diff --git a/retrieval/discovery/file_test.go b/retrieval/discovery/file_test.go
index 4c1407666a..2e1babce14 100644
--- a/retrieval/discovery/file_test.go
+++ b/retrieval/discovery/file_test.go
@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
 )
@@ -27,17 +28,17 @@ func testFileSD(t *testing.T, ext string) {
 	conf.RefreshInterval = model.Duration(1 * time.Hour)
 
 	var (
-		fsd  = NewFileDiscovery(&conf)
-		ch   = make(chan config.TargetGroup)
-		done = make(chan struct{})
+		fsd         = NewFileDiscovery(&conf)
+		ch          = make(chan []*config.TargetGroup)
+		ctx, cancel = context.WithCancel(context.Background())
 	)
-	go fsd.Run(ch, done)
+	go fsd.Run(ctx, ch)
 
 	select {
 	case <-time.After(25 * time.Millisecond):
 		// Expected.
-	case tg := <-ch:
-		t.Fatalf("Unexpected target group in file discovery: %s", tg)
+	case tgs := <-ch:
+		t.Fatalf("Unexpected target groups in file discovery: %s", tgs)
 	}
 
 	newf, err := os.Create("fixtures/_test" + ext)
@@ -58,37 +59,37 @@ func testFileSD(t *testing.T, ext string) {
 	}
 	newf.Close()
 
-	// The files contain two target groups which are read and sent in order.
+	// The files contain two target groups.
 	select {
 	case <-time.After(15 * time.Second):
 		t.Fatalf("Expected new target group but got none")
-	case tg := <-ch:
+	case tgs := <-ch:
+		tg := tgs[0]
+
 		if _, ok := tg.Labels["foo"]; !ok {
 			t.Fatalf("Label not parsed")
 		}
 		if tg.String() != fmt.Sprintf("fixtures/_test%s:0", ext) {
 			t.Fatalf("Unexpected target group %s", tg)
 		}
-	}
-	select {
-	case <-time.After(15 * time.Second):
-		t.Fatalf("Expected new target group but got none")
-	case tg := <-ch:
+
+		tg = tgs[1]
 		if tg.String() != fmt.Sprintf("fixtures/_test%s:1", ext) {
-			t.Fatalf("Unexpected target group %s", tg)
+			t.Fatalf("Unexpected target groups %s", tg)
 		}
 	}
+
 	// Based on unknown circumstances, sometimes fsnotify will trigger more events in
 	// some runs (which might be empty, chains of different operations etc.).
 	// We have to drain those (as the target manager would) to avoid deadlocking and must
 	// not try to make sense of it all...
 	drained := make(chan struct{})
 	go func() {
-		for tg := range ch {
+		for tgs := range ch {
 			// Below we will change the file to a bad syntax. Previously extracted target
 			// groups must not be deleted via sending an empty target group.
-			if len(tg.Targets) == 0 {
-				t.Errorf("Unexpected empty target group received: %s", tg)
+			if len(tgs[0].Targets) == 0 {
+				t.Errorf("Unexpected empty target groups received: %s", tgs)
 			}
 		}
 		close(drained)
@@ -107,6 +108,6 @@ func testFileSD(t *testing.T, ext string) {
 
 	os.Rename(newf.Name(), "fixtures/_test"+ext)
 
-	close(done)
+	cancel()
 	<-drained
 }
diff --git a/retrieval/discovery/kubernetes/discovery.go b/retrieval/discovery/kubernetes/discovery.go
index a23a3e08e4..fd7974f8f0 100644
--- a/retrieval/discovery/kubernetes/discovery.go
+++ b/retrieval/discovery/kubernetes/discovery.go
@@ -25,6 +25,7 @@ import (
 
 	"github.com/prometheus/common/log"
 	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/util/httputil"
@@ -94,75 +95,35 @@ func (kd *Discovery) Initialize() error {
 	return nil
 }
 
-// Sources implements the TargetProvider interface.
-func (kd *Discovery) Sources() []string {
-	sourceNames := make([]string, 0, len(kd.apiServers))
-	for _, apiServer := range kd.apiServers {
-		sourceNames = append(sourceNames, apiServersTargetGroupName+":"+apiServer.Host)
-	}
-
-	nodes, _, err := kd.getNodes()
-	if err != nil {
-		// If we can't list nodes then we can't watch them. Assume this is a misconfiguration
-		// & log & return empty.
-		log.Errorf("Unable to initialize Kubernetes nodes: %s", err)
-		return []string{}
-	}
-	sourceNames = append(sourceNames, kd.nodeSources(nodes)...)
-
-	services, _, err := kd.getServices()
-	if err != nil {
-		// If we can't list services then we can't watch them. Assume this is a misconfiguration
-		// & log & return empty.
-		log.Errorf("Unable to initialize Kubernetes services: %s", err)
-		return []string{}
-	}
-	sourceNames = append(sourceNames, kd.serviceSources(services)...)
-
-	return sourceNames
-}
-
-func (kd *Discovery) nodeSources(nodes map[string]*Node) []string {
-	var sourceNames []string
-	for name := range nodes {
-		sourceNames = append(sourceNames, nodesTargetGroupName+":"+name)
-	}
-	return sourceNames
-}
-
-func (kd *Discovery) serviceSources(services map[string]map[string]*Service) []string {
-	var sourceNames []string
-	for _, ns := range services {
-		for _, service := range ns {
-			sourceNames = append(sourceNames, serviceSource(service))
-		}
-	}
-	return sourceNames
-}
-
 // Run implements the TargetProvider interface.
-func (kd *Discovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (kd *Discovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	defer close(ch)
 
-	if tg := kd.updateAPIServersTargetGroup(); tg != nil {
-		select {
-		case ch <- *tg:
-		case <-done:
-			return
-		}
+	// Send an initial full view.
+	// TODO(fabxc): this does not include all available services and service
+	// endpoints yet. Service endpoints were also missing in the previous Sources() method.
+	var all []*config.TargetGroup
+
+	all = append(all, kd.updateAPIServersTargetGroup())
+	all = append(all, kd.updateNodesTargetGroup())
+
+	select {
+	case ch <- all:
+	case <-ctx.Done():
+		return
 	}
 
 	retryInterval := time.Duration(kd.Conf.RetryInterval)
 
 	update := make(chan interface{}, 10)
 
-	go kd.watchNodes(update, done, retryInterval)
-	go kd.startServiceWatch(update, done, retryInterval)
+	go kd.watchNodes(update, ctx.Done(), retryInterval)
+	go kd.startServiceWatch(update, ctx.Done(), retryInterval)
 
 	var tg *config.TargetGroup
 	for {
 		select {
-		case <-done:
+		case <-ctx.Done():
 			return
 		case event := <-update:
 			switch obj := event.(type) {
@@ -181,8 +142,8 @@ func (kd *Discovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
 		}
 
 		select {
-		case ch <- *tg:
-		case <-done:
+		case ch <- []*config.TargetGroup{tg}:
+		case <-ctx.Done():
 			return
 		}
 	}
diff --git a/retrieval/discovery/marathon.go b/retrieval/discovery/marathon.go
index 181ea440f4..6361a78732 100644
--- a/retrieval/discovery/marathon.go
+++ b/retrieval/discovery/marathon.go
@@ -17,6 +17,8 @@ import (
 	"time"
 
 	"github.com/prometheus/common/log"
+	"golang.org/x/net/context"
+
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/retrieval/discovery/marathon"
 )
@@ -40,25 +42,13 @@ func NewMarathonDiscovery(conf *config.MarathonSDConfig) *MarathonDiscovery {
 	}
 }
 
-// Sources implements the TargetProvider interface.
-func (md *MarathonDiscovery) Sources() []string {
-	var sources []string
-	tgroups, err := md.fetchTargetGroups()
-	if err == nil {
-		for source := range tgroups {
-			sources = append(sources, source)
-		}
-	}
-	return sources
-}
-
 // Run implements the TargetProvider interface.
-func (md *MarathonDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (md *MarathonDiscovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	defer close(ch)
 
 	for {
 		select {
-		case <-done:
+		case <-ctx.Done():
 			return
 		case <-time.After(md.refreshInterval):
 			err := md.updateServices(ch)
@@ -69,23 +59,24 @@ func (md *MarathonDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struc
 	}
 }
 
-func (md *MarathonDiscovery) updateServices(ch chan<- config.TargetGroup) error {
+func (md *MarathonDiscovery) updateServices(ch chan<- []*config.TargetGroup) error {
 	targetMap, err := md.fetchTargetGroups()
 	if err != nil {
 		return err
 	}
 
-	// Update services which are still present
+	all := make([]*config.TargetGroup, 0, len(targetMap))
 	for _, tg := range targetMap {
-		ch <- *tg
+		all = append(all, tg)
 	}
+	ch <- all
 
 	// Remove services which did disappear
 	for source := range md.lastRefresh {
 		_, ok := targetMap[source]
 		if !ok {
 			log.Debugf("Removing group for %s", source)
-			ch <- config.TargetGroup{Source: source}
+			ch <- []*config.TargetGroup{{Source: source}}
 		}
 	}
 
diff --git a/retrieval/discovery/marathon_test.go b/retrieval/discovery/marathon_test.go
index f54d828077..cc58a13808 100644
--- a/retrieval/discovery/marathon_test.go
+++ b/retrieval/discovery/marathon_test.go
@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/retrieval/discovery/marathon"
@@ -26,8 +27,8 @@ import (
 
 var marathonValidLabel = map[string]string{"prometheus": "yes"}
 
-func newTestDiscovery(client marathon.AppListClient) (chan config.TargetGroup, *MarathonDiscovery) {
-	ch := make(chan config.TargetGroup)
+func newTestDiscovery(client marathon.AppListClient) (chan []*config.TargetGroup, *MarathonDiscovery) {
+	ch := make(chan []*config.TargetGroup)
 	md := NewMarathonDiscovery(&config.MarathonSDConfig{
 		Servers: []string{"http://localhost:8080"},
 	})
@@ -60,7 +61,9 @@ func TestMarathonSDEmptyList(t *testing.T) {
 	go func() {
 		select {
 		case tg := <-ch:
-			t.Fatalf("Got group: %v", tg)
+			if len(tg) > 0 {
+				t.Fatalf("Got group: %v", tg)
+			}
 		default:
 		}
 	}()
@@ -96,7 +99,9 @@ func TestMarathonSDSendGroup(t *testing.T) {
 	})
 	go func() {
 		select {
-		case tg := <-ch:
+		case tgs := <-ch:
+			tg := tgs[0]
+
 			if tg.Source != "test-service" {
 				t.Fatalf("Wrong target group name: %s", tg.Source)
 			}
@@ -121,9 +126,10 @@ func TestMarathonSDRemoveApp(t *testing.T) {
 	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
 		return marathonTestAppList(marathonValidLabel, 1), nil
 	})
+
 	go func() {
-		up1 := <-ch
-		up2 := <-ch
+		up1 := (<-ch)[0]
+		up2 := (<-ch)[0]
 		if up2.Source != up1.Source {
 			t.Fatalf("Source is different: %s", up2)
 			if len(up2.Targets) > 0 {
@@ -145,33 +151,25 @@ func TestMarathonSDRemoveApp(t *testing.T) {
 	}
 }
 
-func TestMarathonSDSources(t *testing.T) {
-	_, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
-		return marathonTestAppList(marathonValidLabel, 1), nil
-	})
-	sources := md.Sources()
-	if len(sources) != 1 {
-		t.Fatalf("Wrong number of sources: %s", sources)
-	}
-}
-
 func TestMarathonSDRunAndStop(t *testing.T) {
 	ch, md := newTestDiscovery(func(url string) (*marathon.AppList, error) {
 		return marathonTestAppList(marathonValidLabel, 1), nil
 	})
 	md.refreshInterval = time.Millisecond * 10
-	done := make(chan struct{})
+	ctx, cancel := context.WithCancel(context.Background())
 
 	go func() {
 		select {
 		case <-ch:
-			close(done)
+			cancel()
 		case <-time.After(md.refreshInterval * 3):
-			close(done)
+			cancel()
 			t.Fatalf("Update took too long.")
 		}
 	}()
-	md.Run(ch, done)
+
+	md.Run(ctx, ch)
+
 	select {
 	case <-ch:
 	default:
diff --git a/retrieval/discovery/nerve.go b/retrieval/discovery/nerve.go
index d234160627..f99c9d61f5 100644
--- a/retrieval/discovery/nerve.go
+++ b/retrieval/discovery/nerve.go
@@ -21,6 +21,7 @@ import (
 
 	"github.com/prometheus/common/model"
 	"github.com/samuel/go-zookeeper/zk"
+	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/util/treecache"
@@ -47,7 +48,7 @@ type NerveDiscovery struct {
 	conn       *zk.Conn
 	mu         sync.RWMutex
 	sources    map[string]*config.TargetGroup
-	sdUpdates  *chan<- config.TargetGroup
+	sdUpdates  *chan<- []*config.TargetGroup
 	updates    chan treecache.ZookeeperTreeCacheEvent
 	treeCaches []*treecache.ZookeeperTreeCache
 }
@@ -73,17 +74,6 @@ func NewNerveDiscovery(conf *config.NerveSDConfig) *NerveDiscovery {
 	return sd
 }
 
-// Sources implements the TargetProvider interface.
-func (sd *NerveDiscovery) Sources() []string {
-	sd.mu.RLock()
-	defer sd.mu.RUnlock()
-	srcs := []string{}
-	for t := range sd.sources {
-		srcs = append(srcs, t)
-	}
-	return srcs
-}
-
 func (sd *NerveDiscovery) processUpdates() {
 	defer sd.conn.Close()
 	for event := range sd.updates {
@@ -104,7 +94,7 @@ func (sd *NerveDiscovery) processUpdates() {
 		}
 		sd.mu.Unlock()
 		if sd.sdUpdates != nil {
-			*sd.sdUpdates <- *tg
+			*sd.sdUpdates <- []*config.TargetGroup{tg}
 		}
 	}
 
@@ -114,17 +104,22 @@ func (sd *NerveDiscovery) processUpdates() {
 }
 
 // Run implements the TargetProvider interface.
-func (sd *NerveDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (sd *NerveDiscovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	// Send on everything we have seen so far.
 	sd.mu.Lock()
-	for _, targetGroup := range sd.sources {
-		ch <- *targetGroup
+
+	all := make([]*config.TargetGroup, 0, len(sd.sources))
+
+	for _, tg := range sd.sources {
+		all = append(all, tg)
 	}
+	ch <- all
+
 	// Tell processUpdates to send future updates.
 	sd.sdUpdates = &ch
 	sd.mu.Unlock()
 
-	<-done
+	<-ctx.Done()
 	for _, tc := range sd.treeCaches {
 		tc.Stop()
 	}
diff --git a/retrieval/discovery/serverset.go b/retrieval/discovery/serverset.go
index d1172b2438..5a13af63cc 100644
--- a/retrieval/discovery/serverset.go
+++ b/retrieval/discovery/serverset.go
@@ -22,6 +22,7 @@ import (
 
 	"github.com/prometheus/common/model"
 	"github.com/samuel/go-zookeeper/zk"
+	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/util/strutil"
@@ -57,7 +58,7 @@ type ServersetDiscovery struct {
 	conn       *zk.Conn
 	mu         sync.RWMutex
 	sources    map[string]*config.TargetGroup
-	sdUpdates  *chan<- config.TargetGroup
+	sdUpdates  *chan<- []*config.TargetGroup
 	updates    chan treecache.ZookeeperTreeCacheEvent
 	treeCaches []*treecache.ZookeeperTreeCache
 }
@@ -83,17 +84,6 @@ func NewServersetDiscovery(conf *config.ServersetSDConfig) *ServersetDiscovery {
 	return sd
 }
 
-// Sources implements the TargetProvider interface.
-func (sd *ServersetDiscovery) Sources() []string {
-	sd.mu.RLock()
-	defer sd.mu.RUnlock()
-	srcs := []string{}
-	for t := range sd.sources {
-		srcs = append(srcs, t)
-	}
-	return srcs
-}
-
 func (sd *ServersetDiscovery) processUpdates() {
 	defer sd.conn.Close()
 	for event := range sd.updates {
@@ -114,7 +104,7 @@ func (sd *ServersetDiscovery) processUpdates() {
 		}
 		sd.mu.Unlock()
 		if sd.sdUpdates != nil {
-			*sd.sdUpdates <- *tg
+			*sd.sdUpdates <- []*config.TargetGroup{tg}
 		}
 	}
 
@@ -124,17 +114,22 @@ func (sd *ServersetDiscovery) processUpdates() {
 }
 
 // Run implements the TargetProvider interface.
-func (sd *ServersetDiscovery) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
+func (sd *ServersetDiscovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
 	// Send on everything we have seen so far.
 	sd.mu.Lock()
-	for _, targetGroup := range sd.sources {
-		ch <- *targetGroup
+
+	all := make([]*config.TargetGroup, 0, len(sd.sources))
+
+	for _, tg := range sd.sources {
+		all = append(all, tg)
 	}
+	ch <- all
+
 	// Tell processUpdates to send future updates.
 	sd.sdUpdates = &ch
 	sd.mu.Unlock()
 
-	<-done
+	<-ctx.Done()
 	for _, tc := range sd.treeCaches {
 		tc.Stop()
 	}
@@ -142,8 +137,8 @@ func (sd *ServersetDiscovery) Run(ch chan<- config.TargetGroup, done <-chan stru
 
 func parseServersetMember(data []byte, path string) (*model.LabelSet, error) {
 	member := serversetMember{}
-	err := json.Unmarshal(data, &member)
-	if err != nil {
+
+	if err := json.Unmarshal(data, &member); err != nil {
 		return nil, fmt.Errorf("error unmarshaling serverset member %q: %s", path, err)
 	}
 
diff --git a/retrieval/targetmanager.go b/retrieval/targetmanager.go
index e223cc332e..7328c9e03f 100644
--- a/retrieval/targetmanager.go
+++ b/retrieval/targetmanager.go
@@ -40,7 +40,7 @@ type TargetProvider interface {
 	// updated target groups. The channel must be closed by the target provider
 	// if no more updates will be sent.
 	// On receiving from done Run must return.
-	Run(up chan<- config.TargetGroup, done <-chan struct{})
+	Run(ctx context.Context, up chan<- []*config.TargetGroup)
 }
 
 // TargetManager maintains a set of targets, starts and stops their scraping and
@@ -178,7 +178,7 @@ func (ss *scrapeSet) run(ctx context.Context) {
 
 	for name, prov := range providers {
 		var (
-			updates = make(chan config.TargetGroup)
+			updates = make(chan []*config.TargetGroup)
 		)
 
 		wg.Add(1)
@@ -192,23 +192,17 @@ func (ss *scrapeSet) run(ctx context.Context) {
 				case <-ctx.Done():
 					ss.stopScrapers(name)
 					return
-				case update := <-updates:
-					if err := ss.update(name, &update); err != nil {
-						log.With("target_group", update).Errorf("Target update failed: %s", err)
+				case tgs := <-updates:
+					for _, tg := range tgs {
+						if err := ss.update(name, tg); err != nil {
+							log.With("target_group", tg).Errorf("Target update failed: %s", err)
+						}
 					}
 				}
 			}
 		}(name, prov)
 
-		done := make(chan struct{})
-
-		// TODO(fabxc): Adjust the TargetProvider interface so we can remove this
-		// redirection of the termination signal.
-		go func() {
-			<-ctx.Done()
-			close(done)
-		}()
-		go prov.Run(updates, done)
+		go prov.Run(ctx, updates)
 	}
 
 	wg.Wait()
@@ -421,21 +415,16 @@ func NewStaticProvider(groups []*config.TargetGroup) *StaticProvider {
 	for i, tg := range groups {
 		tg.Source = fmt.Sprintf("%d", i)
 	}
-	return &StaticProvider{
-		TargetGroups: groups,
-	}
+	return &StaticProvider{groups}
 }
 
 // Run implements the TargetProvider interface.
-func (sd *StaticProvider) Run(ch chan<- config.TargetGroup, done <-chan struct{}) {
-	defer close(ch)
-
-	for _, tg := range sd.TargetGroups {
-		select {
-		case <-done:
-			return
-		case ch <- *tg:
-		}
+func (sd *StaticProvider) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
+	// We still have to consider that the consumer exits right away in which case
+	// the context will be canceled.
+	select {
+	case ch <- sd.TargetGroups:
+	case <-ctx.Done():
 	}
-	<-done
+	close(ch)
 }