Allow replacing job targets via HTTP API.

This roughly comprises the following changes:

- index target pools by job instead of scrape interval
- make targets within a pool exchangable while preserving existing
  health state for targets
- allow exchanging targets via HTTP API (PUT)
- show target lists in /status (experimental, for own debug use)

config/config.go

@@ -58,7 +58,7 @@ func (config *Config) AddJob(options map[string]string, targets []Targets) error
 	if len(targets) == 0 {
 		return fmt.Errorf("No targets configured for job '%v'", name)
 	}
-	job := &JobConfig{
+	job := JobConfig{
 		Targets: tmpJobTargets,
 	}
 	for option, value := range options {
@@ -66,10 +66,20 @@ func (config *Config) AddJob(options map[string]string, targets []Targets) error
 			return err
 		}
 	}
-	config.Jobs = append(config.Jobs, *job)
+	config.Jobs = append(config.Jobs, job)
 	return nil
 }
 
+func (config *Config) GetJobByName(name string) (jobConfig *JobConfig) {
+	for _, job := range config.Jobs {
+		if job.Name == name {
+			jobConfig = &job
+			break
+		}
+	}
+	return
+}
+
 func (config *GlobalConfig) SetOption(option string, value string) (err error) {
 	switch option {
 	case "scrape_interval":

retrieval/target.go

@@ -79,8 +79,12 @@ type Target interface {
 	// points in this interface, this one is the best candidate to change given
 	// the ways to express the endpoint.
 	Address() string
-	// How frequently queries occur.
-	Interval() time.Duration
+	// Return the target's base labels.
+	BaseLabels() model.LabelSet
+	// Merge a new externally supplied target definition (e.g. with changed base
+	// labels) into an old target definition for the same endpoint. Preserve
+	// remaining information - like health state - from the old target.
+	Merge(newTarget Target)
 }
 
 // target is a Target that refers to a singular HTTP or HTTPS endpoint.
@@ -94,19 +98,15 @@ type target struct {
 	// What is the deadline for the HTTP or HTTPS against this endpoint.
 	Deadline time.Duration
 	// Any base labels that are added to this target and its metrics.
-	BaseLabels model.LabelSet
-
-	// XXX: Move this to a field with the target manager initialization instead of here.
-	interval time.Duration
+	baseLabels model.LabelSet
 }
 
 // Furnish a reasonably configured target for querying.
-func NewTarget(address string, interval, deadline time.Duration, baseLabels model.LabelSet) Target {
+func NewTarget(address string, deadline time.Duration, baseLabels model.LabelSet) Target {
 	target := &target{
 		address:    address,
 		Deadline:   deadline,
-		interval:   interval,
-		BaseLabels: baseLabels,
+		baseLabels: baseLabels,
 	}
 
 	scheduler := &healthScheduler{
@@ -155,7 +155,7 @@ func (t *target) Scrape(earliest time.Time, results chan format.Result) (err err
 		// XXX: This is a wart; we need to handle this more gracefully down the
 		//      road, especially once we have service discovery support.
 		baseLabels := model.LabelSet{instance: model.LabelValue(t.Address())}
-		for baseLabel, baseValue := range t.BaseLabels {
+		for baseLabel, baseValue := range t.baseLabels {
 			baseLabels[baseLabel] = baseValue
 		}
 
@@ -200,6 +200,16 @@ func (t target) Address() string {
 	return t.address
 }
 
-func (t target) Interval() time.Duration {
-	return t.interval
+func (t target) BaseLabels() model.LabelSet {
+	return t.baseLabels
+}
+
+// Merge a new externally supplied target definition (e.g. with changed base
+// labels) into an old target definition for the same endpoint. Preserve
+// remaining information - like health state - from the old target.
+func (t *target) Merge(newTarget Target) {
+	if t.Address() != newTarget.Address() {
+		panic("targets don't refer to the same endpoint")
+	}
+	t.baseLabels = newTarget.BaseLabels()
 }

retrieval/targetmanager.go

@@ -14,7 +14,6 @@
 package retrieval
 
 import (
-	"container/heap"
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/model"
 	"github.com/prometheus/prometheus/retrieval/format"
@@ -25,14 +24,16 @@ import (
 type TargetManager interface {
 	acquire()
 	release()
-	Add(t Target)
+	AddTarget(job *config.JobConfig, t Target, defaultScrapeInterval time.Duration)
+	ReplaceTargets(job *config.JobConfig, newTargets []Target, defaultScrapeInterval time.Duration)
 	Remove(t Target)
 	AddTargetsFromConfig(config *config.Config)
+	Pools() map[string]*TargetPool
 }
 
 type targetManager struct {
 	requestAllowance chan bool
-	pools            map[time.Duration]*TargetPool
+	poolsByJob       map[string]*TargetPool
 	results          chan format.Result
 }
 
@@ -40,7 +41,7 @@ func NewTargetManager(results chan format.Result, requestAllowance int) TargetMa
 	return &targetManager{
 		requestAllowance: make(chan bool, requestAllowance),
 		results:          results,
-		pools:            make(map[time.Duration]*TargetPool),
+		poolsByJob:       make(map[string]*TargetPool),
 	}
 }
 
@@ -52,17 +53,32 @@ func (m *targetManager) release() {
 	<-m.requestAllowance
 }
 
-func (m *targetManager) Add(t Target) {
-	targetPool, ok := m.pools[t.Interval()]
+func (m *targetManager) TargetPoolForJob(job *config.JobConfig, defaultScrapeInterval time.Duration) (targetPool *TargetPool) {
+	targetPool, ok := m.poolsByJob[job.Name]
 
 	if !ok {
 		targetPool = NewTargetPool(m)
-		log.Printf("Pool %s does not exist; creating and starting...", t.Interval())
-		go targetPool.Run(m.results, t.Interval())
-	}
+		log.Printf("Pool for job %s does not exist; creating and starting...", job.Name)
 
-	heap.Push(targetPool, t)
-	m.pools[t.Interval()] = targetPool
+		interval := job.ScrapeInterval
+		if interval == 0 {
+			interval = defaultScrapeInterval
+		}
+		m.poolsByJob[job.Name] = targetPool
+		go targetPool.Run(m.results, interval)
+	}
+	return
+}
+
+func (m *targetManager) AddTarget(job *config.JobConfig, t Target, defaultScrapeInterval time.Duration) {
+	targetPool := m.TargetPoolForJob(job, defaultScrapeInterval)
+	targetPool.AddTarget(t)
+	m.poolsByJob[job.Name] = targetPool
+}
+
+func (m *targetManager) ReplaceTargets(job *config.JobConfig, newTargets []Target, defaultScrapeInterval time.Duration) {
+	targetPool := m.TargetPoolForJob(job, defaultScrapeInterval)
+	targetPool.replaceTargets(newTargets)
 }
 
 func (m targetManager) Remove(t Target) {
@@ -79,15 +95,15 @@ func (m *targetManager) AddTargetsFromConfig(config *config.Config) {
 				baseLabels[label] = value
 			}
 
-			interval := job.ScrapeInterval
-			if interval == 0 {
-				interval = config.Global.ScrapeInterval
-			}
-
 			for _, endpoint := range configTargets.Endpoints {
-				target := NewTarget(endpoint, interval, time.Second*5, baseLabels)
-				m.Add(target)
+				target := NewTarget(endpoint, time.Second*5, baseLabels)
+				m.AddTarget(&job, target, config.Global.ScrapeInterval)
 			}
 		}
 	}
 }
+
+// XXX: Not really thread-safe. Only used in /status page for now.
+func (m *targetManager) Pools() map[string]*TargetPool {
+	return m.poolsByJob
+}

retrieval/targetmanager_test.go

@@ -14,6 +14,8 @@
 package retrieval
 
 import (
+	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/model"
 	"github.com/prometheus/prometheus/retrieval/format"
 	"github.com/prometheus/prometheus/utility/test"
 	"testing"
@@ -31,6 +33,10 @@ func (t fakeTarget) Address() string {
 	return "fake"
 }
 
+func (t fakeTarget) BaseLabels() model.LabelSet {
+	return model.LabelSet{}
+}
+
 func (t fakeTarget) Interval() time.Duration {
 	return t.interval
 }
@@ -52,9 +58,17 @@ func (t *fakeTarget) scheduledFor() (time time.Time) {
 	return
 }
 
+func (t *fakeTarget) Merge(newTarget Target) {}
+
 func testTargetManager(t test.Tester) {
 	results := make(chan format.Result, 5)
 	targetManager := NewTargetManager(results, 3)
+	testJob1 := &config.JobConfig{
+		Name: "test_job1",
+	}
+	testJob2 := &config.JobConfig{
+		Name: "test_job2",
+	}
 
 	target1GroupA := &fakeTarget{
 		schedules: []time.Time{time.Now()},
@@ -65,16 +79,15 @@ func testTargetManager(t test.Tester) {
 		interval:  time.Minute,
 	}
 
-	targetManager.Add(target1GroupA)
-	targetManager.Add(target2GroupA)
+	targetManager.AddTarget(testJob1, target1GroupA, 0)
+	targetManager.AddTarget(testJob1, target2GroupA, 0)
 
 	target1GroupB := &fakeTarget{
 		schedules: []time.Time{time.Now()},
 		interval:  time.Minute * 2,
 	}
 
-	targetManager.Add(target1GroupB)
-
+	targetManager.AddTarget(testJob2, target1GroupB, 0)
 }
 
 func TestTargetManager(t *testing.T) {

retrieval/targetpool.go

@@ -1,9 +1,22 @@
+// Copyright 2013 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package retrieval
 
 import (
-	"container/heap"
 	"github.com/prometheus/prometheus/retrieval/format"
 	"log"
+	"sort"
 	"time"
 )
 
@@ -15,11 +28,15 @@ type TargetPool struct {
 	done                chan bool
 	manager             TargetManager
 	targets             []Target
+	addTargetQueue      chan Target
+	replaceTargetsQueue chan []Target
 }
 
 func NewTargetPool(m TargetManager) (p *TargetPool) {
 	return &TargetPool{
 		manager:             m,
+		addTargetQueue:      make(chan Target),
+		replaceTargetsQueue: make(chan []Target),
 	}
 }
 
@@ -31,20 +48,6 @@ func (p TargetPool) Less(i, j int) bool {
 	return p.targets[i].scheduledFor().Before(p.targets[j].scheduledFor())
 }
 
-func (p *TargetPool) Pop() interface{} {
-	oldPool := p.targets
-	futureLength := p.Len() - 1
-	element := oldPool[futureLength]
-	futurePool := oldPool[0:futureLength]
-	p.targets = futurePool
-
-	return element
-}
-
-func (p *TargetPool) Push(element interface{}) {
-	p.targets = append(p.targets, element.(Target))
-}
-
 func (p TargetPool) Swap(i, j int) {
 	p.targets[i], p.targets[j] = p.targets[j], p.targets[i]
 }
@@ -56,6 +59,10 @@ func (p *TargetPool) Run(results chan format.Result, interval time.Duration) {
 		select {
 		case <-ticker:
 			p.runIteration(results, interval)
+		case newTarget := <-p.addTargetQueue:
+			p.addTarget(newTarget)
+		case newTargets := <-p.replaceTargetsQueue:
+			p.replaceTargets(newTargets)
 		case <-p.done:
 			log.Printf("TargetPool exiting...")
 			break
@@ -67,6 +74,33 @@ func (p TargetPool) Stop() {
 	p.done <- true
 }
 
+func (p *TargetPool) AddTarget(target Target) {
+	p.addTargetQueue <- target
+}
+
+func (p *TargetPool) addTarget(target Target) {
+	p.targets = append(p.targets, target)
+}
+
+func (p *TargetPool) ReplaceTargets(newTargets []Target) {
+	p.replaceTargetsQueue <- newTargets
+}
+
+func (p *TargetPool) replaceTargets(newTargets []Target) {
+	// Replace old target list by new one, but reuse those targets from the old
+	// list of targets which are also in the new list (to preserve scheduling and
+	// health state).
+	for j, newTarget := range newTargets {
+		for _, oldTarget := range p.targets {
+			if oldTarget.Address() == newTarget.Address() {
+				oldTarget.Merge(newTargets[j])
+				newTargets[j] = oldTarget
+			}
+		}
+	}
+	p.targets = newTargets
+}
+
 func (p *TargetPool) runSingle(earliest time.Time, results chan format.Result, t Target) {
 	p.manager.acquire()
 	defer p.manager.release()
@@ -80,33 +114,35 @@ func (p *TargetPool) runIteration(results chan format.Result, interval time.Dura
 	targetCount := p.Len()
 	finished := make(chan bool, targetCount)
 
-	for i := 0; i < targetCount; i++ {
-		target := heap.Pop(p).(Target)
-		if target == nil {
-			break
-		}
+	// Sort p.targets by next scheduling time so we can process the earliest
+	// targets first.
+	sort.Sort(p)
 
+	for _, target := range p.targets {
 		now := time.Now()
 
 		if target.scheduledFor().After(now) {
-			heap.Push(p, target)
 			// None of the remaining targets are ready to be scheduled. Signal that
 			// we're done processing them in this scrape iteration.
-			for j := i; j < targetCount; j++ {
 			finished <- true
-			}
-			break
+			continue
 		}
 
-		go func() {
-			p.runSingle(now, results, target)
-			heap.Push(p, target)
+		go func(t Target) {
+			p.runSingle(now, results, t)
 			finished <- true
-		}()
+		}(target)
 	}
 
-	for i := 0; i < targetCount; i++ {
-		<-finished
+	for i := 0; i < targetCount; {
+		select {
+		case <-finished:
+			i++
+		case newTarget := <-p.addTargetQueue:
+			p.addTarget(newTarget)
+		case newTargets := <-p.replaceTargetsQueue:
+			p.replaceTargets(newTargets)
+		}
 	}
 
 	close(finished)
@@ -114,3 +150,8 @@ func (p *TargetPool) runIteration(results chan format.Result, interval time.Dura
 	duration := float64(time.Since(begin) / time.Millisecond)
 	retrievalDurations.Add(map[string]string{intervalKey: interval.String()}, duration)
 }
+
+// XXX: Not really thread-safe. Only used in /status page for now.
+func (p *TargetPool) Targets() []Target {
+	return p.targets
+}

retrieval/targetpool_test.go

@@ -14,9 +14,9 @@
 package retrieval
 
 import (
-	"container/heap"
 	"github.com/prometheus/prometheus/retrieval/format"
 	"github.com/prometheus/prometheus/utility/test"
+	"sort"
 	"testing"
 	"time"
 )
@@ -111,34 +111,20 @@ func testTargetPool(t test.Tester) {
 				scheduler: literalScheduler(input.scheduledFor),
 			}
 
-			heap.Push(&pool, &target)
+			pool.addTarget(&target)
 		}
-
-		targets := []Target{}
+		sort.Sort(pool)
 
 		if pool.Len() != len(scenario.outputs) {
 			t.Errorf("%s %d. expected TargetPool size to be %d but was %d", scenario.name, i, len(scenario.outputs), pool.Len())
 		} else {
 			for j, output := range scenario.outputs {
-				target := heap.Pop(&pool).(Target)
+				target := pool.targets[j]
 
 				if target.Address() != output.address {
 					t.Errorf("%s %d.%d. expected Target address to be %s but was %s", scenario.name, i, j, output.address, target.Address())
 
 				}
-				targets = append(targets, target)
-			}
-
-			if pool.Len() != 0 {
-				t.Errorf("%s %d. expected pool to be empty, had %d", scenario.name, i, pool.Len())
-			}
-
-			if len(targets) != len(scenario.outputs) {
-				t.Errorf("%s %d. expected to receive %d elements, got %d", scenario.name, i, len(scenario.outputs), len(targets))
-			}
-
-			for _, target := range targets {
-				heap.Push(&pool, target)
 			}
 
 			if pool.Len() != len(scenario.outputs) {
@@ -158,7 +144,7 @@ func TestTargetPoolIterationWithUnhealthyTargetsFinishes(t *testing.T) {
 		address:   "http://example.com/metrics.json",
 		scheduler: literalScheduler(time.Date(9999, 1, 1, 0, 0, 0, 0, time.UTC)),
 	}
-	pool.Push(target)
+	pool.addTarget(target)
 
 	done := make(chan bool)
 	go func() {
@@ -174,6 +160,49 @@ func TestTargetPoolIterationWithUnhealthyTargetsFinishes(t *testing.T) {
 	}
 }
 
+func TestTargetPoolReplaceTargets(t *testing.T) {
+	pool := TargetPool{}
+	oldTarget1 := &target{
+		address:   "http://example1.com/metrics.json",
+		scheduler: literalScheduler(time.Date(9999, 1, 1, 0, 0, 0, 0, time.UTC)),
+		state:     UNREACHABLE,
+	}
+	oldTarget2 := &target{
+		address:   "http://example2.com/metrics.json",
+		scheduler: literalScheduler(time.Date(7500, 1, 1, 0, 0, 0, 0, time.UTC)),
+		state:     UNREACHABLE,
+	}
+	newTarget1 := &target{
+		address:   "http://example1.com/metrics.json",
+		scheduler: literalScheduler(time.Date(5000, 1, 1, 0, 0, 0, 0, time.UTC)),
+		state:     ALIVE,
+	}
+	newTarget2 := &target{
+		address:   "http://example3.com/metrics.json",
+		scheduler: literalScheduler(time.Date(2500, 1, 1, 0, 0, 0, 0, time.UTC)),
+		state:     ALIVE,
+	}
+
+	pool.addTarget(oldTarget1)
+	pool.addTarget(oldTarget2)
+
+	pool.replaceTargets([]Target{newTarget1, newTarget2})
+	sort.Sort(pool)
+
+	if pool.Len() != 2 {
+		t.Errorf("Expected 2 elements in pool, had %d", pool.Len())
+	}
+
+	target1 := pool.targets[0].(*target)
+	if target1.state != newTarget1.state {
+		t.Errorf("Wrong first target returned from pool, expected %v, got %v", newTarget2, target1)
+	}
+	target2 := pool.targets[1].(*target)
+	if target2.state != oldTarget1.state {
+		t.Errorf("Wrong second target returned from pool, expected %v, got %v", oldTarget1, target2)
+	}
+}
+
 func BenchmarkTargetPool(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		testTargetPool(b)

web/api/api.go

@@ -1,8 +1,21 @@
+// Copyright 2013 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package api
 
 import (
 	"code.google.com/p/gorest"
-	"github.com/prometheus/prometheus/storage/metric"
+	"github.com/prometheus/prometheus/appstate"
 	"github.com/prometheus/prometheus/utility"
 )
 
@@ -13,12 +26,14 @@ type MetricsService struct {
 	queryRange gorest.EndPoint `method:"GET" path:"/query_range?{expr:string}&{end:int64}&{range:int64}&{step:int64}" output:"string"`
 	metrics    gorest.EndPoint `method:"GET" path:"/metrics" output:"string"`
 
-	persistence metric.MetricPersistence
+	setTargets gorest.EndPoint `method:"PUT" path:"/jobs/{jobName:string}/targets" postdata:"[]TargetGroup"`
+
+	appState *appstate.ApplicationState
 	time     utility.Time
 }
 
-func NewMetricsService(persistence metric.MetricPersistence) *MetricsService {
+func NewMetricsService(appState *appstate.ApplicationState) *MetricsService {
 	return &MetricsService{
-		persistence: persistence,
+		appState: appState,
 	}
 }

web/api/query.go

@@ -1,3 +1,16 @@
+// Copyright 2013 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package api
 
 import (
@@ -70,7 +83,7 @@ func (serv MetricsService) QueryRange(Expr string, End int64, Range int64, Step
 }
 
 func (serv MetricsService) Metrics() string {
-	metricNames, err := serv.persistence.GetAllMetricNames()
+	metricNames, err := serv.appState.Persistence.GetAllMetricNames()
 	rb := serv.ResponseBuilder()
 	rb.SetContentType(gorest.Application_Json)
 	if err != nil {

web/api/targets.go

@@ -0,0 +1,48 @@
+// Copyright 2013 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package api
+
+import (
+	"github.com/prometheus/prometheus/model"
+	"github.com/prometheus/prometheus/retrieval"
+	"net/http"
+	"time"
+)
+
+type TargetGroup struct {
+	Endpoints  []string          `json:"endpoints"`
+	BaseLabels map[string]string `json:"baseLabels"`
+}
+
+func (serv MetricsService) SetTargets(targetGroups []TargetGroup, jobName string) {
+	if job := serv.appState.Config.GetJobByName(jobName); job == nil {
+		rb := serv.ResponseBuilder()
+		rb.SetResponseCode(http.StatusNotFound)
+	} else {
+		newTargets := []retrieval.Target{}
+		for _, targetGroup := range targetGroups {
+			// Do mandatory map type conversion due to Go shortcomings.
+			baseLabels := model.LabelSet{}
+			for label, value := range targetGroup.BaseLabels {
+				baseLabels[model.LabelName(label)] = model.LabelValue(value)
+			}
+
+			for _, endpoint := range targetGroup.Endpoints {
+				newTarget := retrieval.NewTarget(endpoint, time.Second*5, baseLabels)
+				newTargets = append(newTargets, newTarget)
+			}
+		}
+		serv.appState.TargetManager.ReplaceTargets(job, newTargets, serv.appState.Config.Global.ScrapeInterval)
+	}
+}

web/status.go

@@ -15,6 +15,7 @@ package web
 
 import (
 	"github.com/prometheus/prometheus/appstate"
+	"github.com/prometheus/prometheus/retrieval"
 	"html/template"
 	"net/http"
 )
@@ -23,7 +24,7 @@ type PrometheusStatus struct {
 	Config      string
 	Rules       string
 	Status      string
-	Targets string
+	TargetPools map[string]*retrieval.TargetPool
 }
 
 type StatusHandler struct {
@@ -35,7 +36,7 @@ func (h *StatusHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		Config:      h.appState.Config.ToString(0),
 		Rules:       "TODO: list rules here",
 		Status:      "TODO: add status information here",
-		Targets: "TODO: list targets here",
+		TargetPools: h.appState.TargetManager.Pools(),
 	}
 	t, _ := template.ParseFiles("web/templates/status.html")
 	t.Execute(w, status)

web/templates/status.html

@@ -27,7 +27,19 @@
 
 		<h2>Targets</h2>
     <div class="grouping_box">
-{{.Targets}}
+      <ul>
+        {{range $job, $pool := .TargetPools}}
+          <li>{{$job}}
+            <ul>
+              {{range $pool.Targets}}
+                <li>
+                <a href="{{.Address}}">{{.Address}}</a> (State: {{.State}}, Base labels: {{.BaseLabels}})
+                </li>
+              {{end}}
+            </ul>
+          </li>
+        {{end}}
+      </ul>
 		</div>
   </body>
 </html>

web/web.go

@@ -29,7 +29,7 @@ var (
 )
 
 func StartServing(appState *appstate.ApplicationState) {
-	gorest.RegisterService(api.NewMetricsService(appState.Persistence))
+	gorest.RegisterService(api.NewMetricsService(appState))
 	exporter := registry.DefaultRegistry.YieldExporter()
 
 	http.Handle("/status", &StatusHandler{appState: appState})