func (kd *Discovery) updateAPIServersTargetGroup() *config.TargetGroup {
	tg := &config.TargetGroup{
		Source: apiServersTargetGroupName,
		Labels: model.LabelSet{
			roleLabel: model.LabelValue("apiserver"),
		},
	}

	for _, apiServer := range kd.apiServers {
		apiServerAddress := apiServer.Host
		_, _, err := net.SplitHostPort(apiServerAddress)
		// If error then no port is specified - use default for scheme.
		if err != nil {
			switch apiServer.Scheme {
			case "http":
				apiServerAddress = net.JoinHostPort(apiServerAddress, "80")
			case "https":
				apiServerAddress = net.JoinHostPort(apiServerAddress, "443")
			}
		}

		t := model.LabelSet{
			model.AddressLabel: model.LabelValue(apiServerAddress),
			model.SchemeLabel:  model.LabelValue(apiServer.Scheme),
		}
		tg.Targets = append(tg.Targets, t)
	}

	return tg
}

func extractUntyped(o *DecodeOptions, f *dto.MetricFamily) model.Vector {
	samples := make(model.Vector, 0, len(f.Metric))

	for _, m := range f.Metric {
		if m.Untyped == nil {
			continue
		}

		lset := make(model.LabelSet, len(m.Label)+1)
		for _, p := range m.Label {
			lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
		}
		lset[model.MetricNameLabel] = model.LabelValue(f.GetName())

		smpl := &model.Sample{
			Metric: model.Metric(lset),
			Value:  model.SampleValue(m.Untyped.GetValue()),
		}

		if m.TimestampMs != nil {
			smpl.Timestamp = model.TimeFromUnixNano(*m.TimestampMs * 1000000)
		} else {
			smpl.Timestamp = o.Timestamp
		}

		samples = append(samples, smpl)
	}

	return samples
}

func TestPrometheus(t *testing.T) {
	Convey("Prometheus", t, func() {

		Convey("converting metric name", func() {
			metric := map[p.LabelName]p.LabelValue{
				p.LabelName("app"):    p.LabelValue("backend"),
				p.LabelName("device"): p.LabelValue("mobile"),
			}

			query := &PrometheusQuery{
				LegendFormat: "legend {{app}} {{ device }} {{broken}}",
			}

			So(formatLegend(metric, query), ShouldEqual, "legend backend mobile {{broken}}")
		})

		Convey("build full serie name", func() {
			metric := map[p.LabelName]p.LabelValue{
				p.LabelName(p.MetricNameLabel): p.LabelValue("http_request_total"),
				p.LabelName("app"):             p.LabelValue("backend"),
				p.LabelName("device"):          p.LabelValue("mobile"),
			}

			query := &PrometheusQuery{
				LegendFormat: "",
			}

			So(formatLegend(metric, query), ShouldEqual, `http_request_total{app="backend", device="mobile"}`)
		})
	})
}

func (kd *Discovery) updateNodesTargetGroup() *config.TargetGroup {
	kd.nodesMu.Lock()
	defer kd.nodesMu.Unlock()

	tg := &config.TargetGroup{
		Source: nodesTargetGroupName,
		Labels: model.LabelSet{
			roleLabel: model.LabelValue("node"),
		},
	}

	// Now let's loop through the nodes & add them to the target group with appropriate labels.
	for nodeName, node := range kd.nodes {
		address := fmt.Sprintf("%s:%d", node.Status.Addresses[0].Address, kd.Conf.KubeletPort)

		t := model.LabelSet{
			model.AddressLabel:  model.LabelValue(address),
			model.InstanceLabel: model.LabelValue(nodeName),
		}
		for k, v := range node.ObjectMeta.Labels {
			labelName := strutil.SanitizeLabelName(nodeLabelPrefix + k)
			t[model.LabelName(labelName)] = model.LabelValue(v)
		}
		tg.Targets = append(tg.Targets, t)
	}

	return tg
}

// alertmanagersFromGroup extracts a list of alertmanagers from a target group and an associcated
// AlertmanagerConfig.
func alertmanagerFromGroup(tg *config.TargetGroup, cfg *config.AlertmanagerConfig) ([]alertmanager, error) {
	var res []alertmanager

	for _, lset := range tg.Targets {
		// Set configured scheme as the initial scheme label for overwrite.
		lset[model.SchemeLabel] = model.LabelValue(cfg.Scheme)
		lset[pathLabel] = model.LabelValue(postPath(cfg.PathPrefix))

		// Combine target labels with target group labels.
		for ln, lv := range tg.Labels {
			if _, ok := lset[ln]; !ok {
				lset[ln] = lv
			}
		}
		lset := relabel.Process(lset, cfg.RelabelConfigs...)
		if lset == nil {
			continue
		}

		// addPort checks whether we should add a default port to the address.
		// If the address is not valid, we don't append a port either.
		addPort := func(s string) bool {
			// If we can split, a port exists and we don't have to add one.
			if _, _, err := net.SplitHostPort(s); err == nil {
				return false
			}
			// If adding a port makes it valid, the previous error
			// was not due to an invalid address and we can append a port.
			_, _, err := net.SplitHostPort(s + ":1234")
			return err == nil
		}
		// If it's an address with no trailing port, infer it based on the used scheme.
		if addr := string(lset[model.AddressLabel]); addPort(addr) {
			// Addresses reaching this point are already wrapped in [] if necessary.
			switch lset[model.SchemeLabel] {
			case "http", "":
				addr = addr + ":80"
			case "https":
				addr = addr + ":443"
			default:
				return nil, fmt.Errorf("invalid scheme: %q", cfg.Scheme)
			}
			lset[model.AddressLabel] = model.LabelValue(addr)
		}
		if err := config.CheckTargetAddress(lset[model.AddressLabel]); err != nil {
			return nil, err
		}

		// Meta labels are deleted after relabelling. Other internal labels propagate to
		// the target which decides whether they will be part of their label set.
		for ln := range lset {
			if strings.HasPrefix(string(ln), model.MetaLabelPrefix) {
				delete(lset, ln)
			}
		}

		res = append(res, alertmanagerLabels(lset))
	}
	return res, nil
}

func TestTargetScrapeScrapeNotFound(t *testing.T) {
	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			w.WriteHeader(http.StatusNotFound)
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	ts := &targetScraper{
		Target: &Target{
			labels: model.LabelSet{
				model.SchemeLabel:  model.LabelValue(serverURL.Scheme),
				model.AddressLabel: model.LabelValue(serverURL.Host),
			},
		},
		client: http.DefaultClient,
	}

	if _, err := ts.scrape(context.Background(), time.Now()); !strings.Contains(err.Error(), "404") {
		t.Fatalf("Expected \"404 NotFound\" error but got: %s", err)
	}
}

func (ed *EC2Discovery) refresh() (*config.TargetGroup, error) {
	ec2s := ec2.New(ed.aws)
	tg := &config.TargetGroup{
		Source: *ed.aws.Region,
	}
	if err := ec2s.DescribeInstancesPages(nil, func(p *ec2.DescribeInstancesOutput, lastPage bool) bool {
		for _, r := range p.Reservations {
			for _, inst := range r.Instances {
				if inst.PrivateIpAddress == nil {
					continue
				}
				labels := model.LabelSet{
					ec2LabelInstanceID: model.LabelValue(*inst.InstanceId),
				}
				if inst.PublicIpAddress != nil {
					labels[ec2LabelPublicIP] = model.LabelValue(*inst.PublicIpAddress)
				}
				labels[ec2LabelPrivateIP] = model.LabelValue(*inst.PrivateIpAddress)
				addr := fmt.Sprintf("%s:%d", *inst.PrivateIpAddress, ed.port)
				labels[model.AddressLabel] = model.LabelValue(addr)
				for _, t := range inst.Tags {
					name := strutil.SanitizeLabelName(*t.Key)
					labels[ec2LabelTag+model.LabelName(name)] = model.LabelValue(*t.Value)
				}
				tg.Targets = append(tg.Targets, labels)
			}
		}
		return true
	}); err != nil {
		return nil, fmt.Errorf("could not describe instances: %s", err)
	}
	return tg, nil
}

func (kd *Discovery) updateNodesTargetGroup() *config.TargetGroup {
	kd.nodesMu.RLock()
	defer kd.nodesMu.RUnlock()

	tg := &config.TargetGroup{
		Source: nodesTargetGroupName,
		Labels: model.LabelSet{
			roleLabel: model.LabelValue("node"),
		},
	}

	// Now let's loop through the nodes & add them to the target group with appropriate labels.
	for nodeName, node := range kd.nodes {
		nodeAddress, err := nodeHostIP(node)
		if err != nil {
			log.Debugf("Skipping node %s: %s", node.Name, err)
			continue
		}

		address := fmt.Sprintf("%s:%d", nodeAddress.String(), kd.Conf.KubeletPort)

		t := model.LabelSet{
			model.AddressLabel:  model.LabelValue(address),
			model.InstanceLabel: model.LabelValue(nodeName),
		}
		for k, v := range node.ObjectMeta.Labels {
			labelName := strutil.SanitizeLabelName(nodeLabelPrefix + k)
			t[model.LabelName(labelName)] = model.LabelValue(v)
		}
		tg.Targets = append(tg.Targets, t)
	}

	return tg
}

// Decode implements the Decoder interface.
func (d *protoDecoder) Decode(v *dto.MetricFamily) error {
	_, err := pbutil.ReadDelimited(d.r, v)
	if err != nil {
		return err
	}
	if !model.IsValidMetricName(model.LabelValue(v.GetName())) {
		return fmt.Errorf("invalid metric name %q", v.GetName())
	}
	for _, m := range v.GetMetric() {
		if m == nil {
			continue
		}
		for _, l := range m.GetLabel() {
			if l == nil {
				continue
			}
			if !model.LabelValue(l.GetValue()).IsValid() {
				return fmt.Errorf("invalid label value %q", l.GetValue())
			}
			if !model.LabelName(l.GetName()).IsValid() {
				return fmt.Errorf("invalid label name %q", l.GetName())
			}
		}
	}
	return nil
}

// watchServices retrieves updates from Consul's services endpoint and sends
// potential updates to the update channel.
func (cd *ConsulDiscovery) watchServices(update chan<- *consulService, done <-chan struct{}) {
	var lastIndex uint64
	for {
		catalog := cd.client.Catalog()
		srvs, meta, err := catalog.Services(&consul.QueryOptions{
			WaitIndex: lastIndex,
			WaitTime:  consulWatchTimeout,
		})
		if err != nil {
			log.Errorf("Error refreshing service list: %s", err)
			time.Sleep(consulRetryInterval)
			continue
		}
		// If the index equals the previous one, the watch timed out with no update.
		if meta.LastIndex == lastIndex {
			continue
		}
		lastIndex = meta.LastIndex

		cd.mu.Lock()
		select {
		case <-done:
			cd.mu.Unlock()
			return
		default:
			// Continue.
		}
		// Check for new services.
		for name := range srvs {
			if _, ok := cd.scrapedServices[name]; len(cd.scrapedServices) > 0 && !ok {
				continue
			}
			srv, ok := cd.services[name]
			if !ok {
				srv = &consulService{
					name:   name,
					tgroup: &config.TargetGroup{},
					done:   make(chan struct{}),
				}
				srv.tgroup.Source = name
				cd.services[name] = srv
			}
			srv.tgroup.Labels = model.LabelSet{
				consulServiceLabel: model.LabelValue(name),
				consulDCLabel:      model.LabelValue(cd.clientDatacenter),
			}
			update <- srv
		}
		// Check for removed services.
		for name, srv := range cd.services {
			if _, ok := srvs[name]; !ok {
				srv.removed = true
				update <- srv
				delete(cd.services, name)
			}
		}
		cd.mu.Unlock()
	}
}

func TestHandlerSend(t *testing.T) {
	var (
		expected model.Alerts
		status   int
	)

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != alertPushEndpoint {
			t.Fatalf("Bad endpoint %q used, expected %q", r.URL.Path, alertPushEndpoint)
		}
		defer r.Body.Close()

		var alerts model.Alerts
		if err := json.NewDecoder(r.Body).Decode(&alerts); err != nil {
			t.Fatalf("Unexpected error on input decoding: %s", err)
		}

		if !alertsEqual(alerts, expected) {
			t.Errorf("%#v %#v", *alerts[0], *expected[0])
			t.Fatalf("Unexpected alerts received %v exp %v", alerts, expected)
		}

		w.WriteHeader(status)
	}))

	defer server.Close()

	h := New(&HandlerOptions{
		AlertmanagerURL: server.URL,
		Timeout:         time.Minute,
		ExternalLabels:  model.LabelSet{"a": "b"},
	})

	for i := range make([]struct{}, maxBatchSize) {
		h.queue = append(h.queue, &model.Alert{
			Labels: model.LabelSet{
				"alertname": model.LabelValue(fmt.Sprintf("%d", i)),
			},
		})
		expected = append(expected, &model.Alert{
			Labels: model.LabelSet{
				"alertname": model.LabelValue(fmt.Sprintf("%d", i)),
				"a":         "b",
			},
		})
	}

	status = http.StatusOK

	if err := h.send(h.queue...); err != nil {
		t.Fatalf("Unexpected error: %s", err)
	}

	status = 500

	if err := h.send(h.queue...); err == nil {
		t.Fatalf("Expected error but got none")
	}
}

func (gd *GCEDiscovery) refresh() (tg *config.TargetGroup, err error) {
	t0 := time.Now()
	defer func() {
		gceSDScrapeDuration.Observe(time.Since(t0).Seconds())
		gceSDScrapesCount.Inc()
		if err != nil {
			gceSDScrapeFailuresCount.Inc()
		}
	}()

	tg = &config.TargetGroup{
		Source: fmt.Sprintf("GCE_%s_%s", gd.project, gd.zone),
	}

	ilc := gd.isvc.List(gd.project, gd.zone)
	if len(gd.filter) > 0 {
		ilc = ilc.Filter(gd.filter)
	}
	err = ilc.Pages(nil, func(l *compute.InstanceList) error {
		for _, inst := range l.Items {
			if len(inst.NetworkInterfaces) == 0 {
				continue
			}
			labels := model.LabelSet{
				gceLabelProject:        model.LabelValue(gd.project),
				gceLabelZone:           model.LabelValue(inst.Zone),
				gceLabelInstanceName:   model.LabelValue(inst.Name),
				gceLabelInstanceStatus: model.LabelValue(inst.Status),
			}
			priIface := inst.NetworkInterfaces[0]
			labels[gceLabelNetwork] = model.LabelValue(priIface.Network)
			labels[gceLabelSubnetwork] = model.LabelValue(priIface.Subnetwork)
			labels[gceLabelPrivateIP] = model.LabelValue(priIface.NetworkIP)
			addr := fmt.Sprintf("%s:%d", priIface.NetworkIP, gd.port)
			labels[model.AddressLabel] = model.LabelValue(addr)

			if inst.Tags != nil && len(inst.Tags.Items) > 0 {
				// We surround the separated list with the separator as well. This way regular expressions
				// in relabeling rules don't have to consider tag positions.
				tags := gd.tagSeparator + strings.Join(inst.Tags.Items, gd.tagSeparator) + gd.tagSeparator
				labels[gceLabelTags] = model.LabelValue(tags)
			}

			if len(priIface.AccessConfigs) > 0 {
				ac := priIface.AccessConfigs[0]
				if ac.Type == "ONE_TO_ONE_NAT" {
					labels[gceLabelPublicIP] = model.LabelValue(ac.NatIP)
				}
			}
			tg.Targets = append(tg.Targets, labels)
		}
		return nil
	})
	if err != nil {
		return tg, fmt.Errorf("error retrieving scrape targets from gce: %s", err)
	}
	return tg, nil
}

func (ed *EC2Discovery) refresh() (*config.TargetGroup, error) {
	ec2s := ec2.New(ed.aws)
	tg := &config.TargetGroup{
		Source: *ed.aws.Region,
	}
	if err := ec2s.DescribeInstancesPages(nil, func(p *ec2.DescribeInstancesOutput, lastPage bool) bool {
		for _, r := range p.Reservations {
			for _, inst := range r.Instances {
				if inst.PrivateIpAddress == nil {
					continue
				}
				labels := model.LabelSet{
					ec2LabelInstanceID: model.LabelValue(*inst.InstanceId),
				}
				labels[ec2LabelPrivateIP] = model.LabelValue(*inst.PrivateIpAddress)
				addr := net.JoinHostPort(*inst.PrivateIpAddress, fmt.Sprintf("%d", ed.port))
				labels[model.AddressLabel] = model.LabelValue(addr)

				if inst.PublicIpAddress != nil {
					labels[ec2LabelPublicIP] = model.LabelValue(*inst.PublicIpAddress)
					labels[ec2LabelPublicDNS] = model.LabelValue(*inst.PublicDnsName)
				}

				labels[ec2LabelAZ] = model.LabelValue(*inst.Placement.AvailabilityZone)
				labels[ec2LabelInstanceState] = model.LabelValue(*inst.State.Name)

				if inst.VpcId != nil {
					labels[ec2LabelVPCID] = model.LabelValue(*inst.VpcId)

					subnetsMap := make(map[string]struct{})
					for _, eni := range inst.NetworkInterfaces {
						subnetsMap[*eni.SubnetId] = struct{}{}
					}
					subnets := []string{}
					for k := range subnetsMap {
						subnets = append(subnets, k)
					}
					labels[ec2LabelSubnetID] = model.LabelValue(
						subnetSeparator +
							strings.Join(subnets, subnetSeparator) +
							subnetSeparator)
				}

				for _, t := range inst.Tags {
					name := strutil.SanitizeLabelName(*t.Key)
					labels[ec2LabelTag+model.LabelName(name)] = model.LabelValue(*t.Value)
				}
				tg.Targets = append(tg.Targets, labels)
			}
		}
		return true
	}); err != nil {
		return nil, fmt.Errorf("could not describe instances: %s", err)
	}
	return tg, nil
}

func relabel(labels model.LabelSet, cfg *config.RelabelConfig) model.LabelSet {
	values := make([]string, 0, len(cfg.SourceLabels))
	for _, ln := range cfg.SourceLabels {
		values = append(values, string(labels[ln]))
	}
	val := strings.Join(values, cfg.Separator)

	switch cfg.Action {
	case config.RelabelDrop:
		if cfg.Regex.MatchString(val) {
			return nil
		}
	case config.RelabelKeep:
		if !cfg.Regex.MatchString(val) {
			return nil
		}
	case config.RelabelReplace:
		indexes := cfg.Regex.FindStringSubmatchIndex(val)
		// If there is no match no replacement must take place.
		if indexes == nil {
			break
		}
		target := model.LabelName(cfg.Regex.ExpandString([]byte{}, cfg.TargetLabel, val, indexes))
		if !target.IsValid() {
			delete(labels, model.LabelName(cfg.TargetLabel))
			break
		}
		res := cfg.Regex.ExpandString([]byte{}, cfg.Replacement, val, indexes)
		if len(res) == 0 {
			delete(labels, model.LabelName(cfg.TargetLabel))
			break
		}
		labels[target] = model.LabelValue(res)
	case config.RelabelHashMod:
		mod := sum64(md5.Sum([]byte(val))) % cfg.Modulus
		labels[model.LabelName(cfg.TargetLabel)] = model.LabelValue(fmt.Sprintf("%d", mod))
	case config.RelabelLabelMap:
		out := make(model.LabelSet, len(labels))
		// Take a copy to avoid infinite loops.
		for ln, lv := range labels {
			out[ln] = lv
		}
		for ln, lv := range labels {
			if cfg.Regex.MatchString(string(ln)) {
				res := cfg.Regex.ReplaceAllString(string(ln), cfg.Replacement)
				out[model.LabelName(res)] = lv
			}
		}
		labels = out
	default:
		panic(fmt.Errorf("retrieval.relabel: unknown relabel action type %q", cfg.Action))
	}
	return labels
}

// Update overwrites settings in the target that are derived from the job config
// it belongs to.
func (t *Target) Update(cfg *config.ScrapeConfig, baseLabels, metaLabels model.LabelSet) {
	t.Lock()
	defer t.Unlock()

	httpClient, err := newHTTPClient(cfg)
	if err != nil {
		log.Errorf("cannot create HTTP client: %v", err)
		return
	}
	t.httpClient = httpClient

	t.url.Scheme = string(baseLabels[model.SchemeLabel])
	t.url.Path = string(baseLabels[model.MetricsPathLabel])

	t.internalLabels = model.LabelSet{}
	t.internalLabels[model.SchemeLabel] = baseLabels[model.SchemeLabel]
	t.internalLabels[model.MetricsPathLabel] = baseLabels[model.MetricsPathLabel]
	t.internalLabels[model.AddressLabel] = model.LabelValue(t.url.Host)

	params := url.Values{}

	for k, v := range cfg.Params {
		params[k] = make([]string, len(v))
		copy(params[k], v)
	}
	for k, v := range baseLabels {
		if strings.HasPrefix(string(k), model.ParamLabelPrefix) {
			if len(params[string(k[len(model.ParamLabelPrefix):])]) > 0 {
				params[string(k[len(model.ParamLabelPrefix):])][0] = string(v)
			} else {
				params[string(k[len(model.ParamLabelPrefix):])] = []string{string(v)}
			}
			t.internalLabels[model.ParamLabelPrefix+k[len(model.ParamLabelPrefix):]] = v
		}
	}
	t.url.RawQuery = params.Encode()

	t.scrapeInterval = time.Duration(cfg.ScrapeInterval)
	t.deadline = time.Duration(cfg.ScrapeTimeout)

	t.honorLabels = cfg.HonorLabels
	t.metaLabels = metaLabels
	t.baseLabels = model.LabelSet{}
	// All remaining internal labels will not be part of the label set.
	for name, val := range baseLabels {
		if !strings.HasPrefix(string(name), model.ReservedLabelPrefix) {
			t.baseLabels[name] = val
		}
	}
	if _, ok := t.baseLabels[model.InstanceLabel]; !ok {
		t.baseLabels[model.InstanceLabel] = model.LabelValue(t.InstanceIdentifier())
	}
	t.metricRelabelConfigs = cfg.MetricRelabelConfigs
}

func targetsForApp(app *App) []model.LabelSet {
	targets := make([]model.LabelSet, 0, len(app.Tasks))
	for _, t := range app.Tasks {
		target := targetForTask(&t)
		targets = append(targets, model.LabelSet{
			model.AddressLabel: model.LabelValue(target),
			taskLabel:          model.LabelValue(t.ID),
		})
	}
	return targets
}

// fullLabels returns the base labels plus internal labels defining the target.
func (t *Target) fullLabels() model.LabelSet {
	t.RLock()
	defer t.RUnlock()
	lset := make(model.LabelSet, len(t.baseLabels)+2)
	for ln, lv := range t.baseLabels {
		lset[ln] = lv
	}
	lset[model.MetricsPathLabel] = model.LabelValue(t.url.Path)
	lset[model.AddressLabel] = model.LabelValue(t.url.Host)
	lset[model.SchemeLabel] = model.LabelValue(t.url.Scheme)
	return lset
}

func TestTargetScrapeScrapeCancel(t *testing.T) {
	block := make(chan struct{})

	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			<-block
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	ts := &targetScraper{
		Target: &Target{
			labels: model.LabelSet{
				model.SchemeLabel:  model.LabelValue(serverURL.Scheme),
				model.AddressLabel: model.LabelValue(serverURL.Host),
			},
		},
		client: http.DefaultClient,
	}
	ctx, cancel := context.WithCancel(context.Background())

	errc := make(chan error)

	go func() {
		time.Sleep(1 * time.Second)
		cancel()
	}()

	go func() {
		if _, err := ts.scrape(ctx, time.Now()); err != context.Canceled {
			errc <- fmt.Errorf("Expected context cancelation error but got: %s", err)
		}
		close(errc)
	}()

	select {
	case <-time.After(5 * time.Second):
		t.Fatalf("Scrape function did not return unexpectedly")
	case err := <-errc:
		if err != nil {
			t.Fatalf(err.Error())
		}
	}
	// If this is closed in a defer above the function the test server
	// does not terminate and the test doens't complete.
	close(block)
}

func TestTargetScraperScrapeOK(t *testing.T) {
	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
			w.Write([]byte("metric_a 1\nmetric_b 2\n"))
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	ts := &targetScraper{
		Target: &Target{
			labels: model.LabelSet{
				model.SchemeLabel:  model.LabelValue(serverURL.Scheme),
				model.AddressLabel: model.LabelValue(serverURL.Host),
			},
		},
		client: http.DefaultClient,
	}
	now := time.Now()

	samples, err := ts.scrape(context.Background(), now)
	if err != nil {
		t.Fatalf("Unexpected scrape error: %s", err)
	}

	expectedSamples := model.Samples{
		{
			Metric:    model.Metric{"__name__": "metric_a"},
			Timestamp: model.TimeFromUnixNano(now.UnixNano()),
			Value:     1,
		},
		{
			Metric:    model.Metric{"__name__": "metric_b"},
			Timestamp: model.TimeFromUnixNano(now.UnixNano()),
			Value:     2,
		},
	}
	sort.Sort(expectedSamples)
	sort.Sort(samples)

	if !reflect.DeepEqual(samples, expectedSamples) {
		t.Errorf("Scraped samples did not match served metrics")
		t.Errorf("Expected: %v", expectedSamples)
		t.Fatalf("Got: %v", samples)
	}
}

func parseServersetMember(data []byte, path string) (model.LabelSet, error) {
	member := serversetMember{}

	if err := json.Unmarshal(data, &member); err != nil {
		return nil, fmt.Errorf("error unmarshaling serverset member %q: %s", path, err)
	}

	labels := model.LabelSet{}
	labels[serversetPathLabel] = model.LabelValue(path)
	labels[model.AddressLabel] = model.LabelValue(
		net.JoinHostPort(member.ServiceEndpoint.Host, fmt.Sprintf("%d", member.ServiceEndpoint.Port)))

	labels[serversetEndpointLabelPrefix+"_host"] = model.LabelValue(member.ServiceEndpoint.Host)
	labels[serversetEndpointLabelPrefix+"_port"] = model.LabelValue(fmt.Sprintf("%d", member.ServiceEndpoint.Port))

	for name, endpoint := range member.AdditionalEndpoints {
		cleanName := model.LabelName(strutil.SanitizeLabelName(name))
		labels[serversetEndpointLabelPrefix+"_host_"+cleanName] = model.LabelValue(
			endpoint.Host)
		labels[serversetEndpointLabelPrefix+"_port_"+cleanName] = model.LabelValue(
			fmt.Sprintf("%d", endpoint.Port))

	}

	labels[serversetStatusLabel] = model.LabelValue(member.Status)
	labels[serversetShardLabel] = model.LabelValue(strconv.Itoa(member.Shard))

	return labels, nil
}