Fix a race in target.go.

Also, fix problems in shutdown.
Starting serving and shutdown still has to be cleaned up properly.
It's a mess.

Change-Id: I51061db12064e434066446e6fceac32741c4f84c

main.go

@@ -86,8 +86,6 @@ func (p *prometheus) interruptHandler() {
 	glog.Warning("Received SIGINT/SIGTERM; Exiting gracefully...")
 
 	p.Close()
-
-	os.Exit(0)
 }
 
 func (p *prometheus) Close() {
@@ -138,7 +136,6 @@ func main() {
 	if err != nil {
 		glog.Fatal("Error opening memory series storage: ", err)
 	}
-	defer memStorage.Close()
 	registry.MustRegister(memStorage)
 
 	var remoteTSDBQueue *remote.TSDBQueueManager
@@ -220,7 +217,6 @@ func main() {
 		storage:         memStorage,
 		remoteTSDBQueue: remoteTSDBQueue,
 	}
-	defer prometheus.Close()
 
 	webService := &web.WebService{
 		StatusHandler:   prometheusStatus,

retrieval/target.go

@@ -126,10 +126,12 @@ type Target interface {
 	GlobalAddress() string
 	// Return the target's base labels.
 	BaseLabels() clientmodel.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)
+	// SetBaseLabelsFrom queues a replacement of the current base labels by
+	// the labels of the given target. The method returns immediately after
+	// queuing. The actual replacement of the base labels happens
+	// asynchronously (but most likely before the next scrape for the target
+	// begins).
+	SetBaseLabelsFrom(Target)
 	// Scrape target at the specified interval.
 	RunScraper(extraction.Ingester, time.Duration)
 	// Stop scraping, synchronous.
@@ -149,6 +151,8 @@ type target struct {
 	// Channel to signal RunScraper should stop, holds a channel
 	// to notify once stopped.
 	stopScraper chan bool
+	// Channel to queue base labels to be replaced.
+	newBaseLabels chan clientmodel.LabelSet
 
 	address string
 	// What is the deadline for the HTTP or HTTPS against this endpoint.
@@ -167,6 +171,7 @@ func NewTarget(address string, deadline time.Duration, baseLabels clientmodel.La
 		baseLabels:    baseLabels,
 		httpClient:    utility.NewDeadlineClient(deadline),
 		stopScraper:   make(chan bool),
+		newBaseLabels: make(chan clientmodel.LabelSet, 1),
 	}
 
 	return target
@@ -197,6 +202,7 @@ func (t *target) recordScrapeHealth(ingester extraction.Ingester, timestamp clie
 	})
 }
 
+// RunScraper implements Target.
 func (t *target) RunScraper(ingester extraction.Ingester, interval time.Duration) {
 	jitterTimer := time.NewTimer(time.Duration(float64(interval) * rand.Float64()))
 	select {
@@ -217,12 +223,15 @@ func (t *target) RunScraper(ingester extraction.Ingester, interval time.Duration
 			targetIntervalLength.WithLabelValues(interval.String()).Observe(float64(time.Since(t.lastScrape) / time.Second))
 			t.lastScrape = time.Now()
 			t.scrape(ingester)
+		case newBaseLabels := <-t.newBaseLabels:
+			t.baseLabels = newBaseLabels
 		case <-t.stopScraper:
 			return
 		}
 	}
 }
 
+// StopScraper implements Target.
 func (t *target) StopScraper() {
 	t.stopScraper <- true
 }
@@ -270,7 +279,7 @@ func (t *target) scrape(ingester extraction.Ingester) (err error) {
 		return err
 	}
 
-	// XXX: This is a wart; we need to handle this more gracefully down the
+	// TODO: This is a wart; we need to handle this more gracefully down the
 	// road, especially once we have service discovery support.
 	baseLabels := clientmodel.LabelSet{InstanceLabel: clientmodel.LabelValue(t.Address())}
 	for baseLabel, baseValue := range t.baseLabels {
@@ -289,22 +298,27 @@ func (t *target) scrape(ingester extraction.Ingester) (err error) {
 	return processor.ProcessSingle(resp.Body, i, processOptions)
 }
 
+// LastError implements Target.
 func (t *target) LastError() error {
 	return t.lastError
 }
 
+// State implements Target.
 func (t *target) State() TargetState {
 	return t.state
 }
 
+// LastScrape implements Target.
 func (t *target) LastScrape() time.Time {
 	return t.lastScrape
 }
 
+// Address implements Target.
 func (t *target) Address() string {
 	return t.address
 }
 
+// GlobalAddress implements Target.
 func (t *target) GlobalAddress() string {
 	address := t.address
 	hostname, err := os.Hostname()
@@ -318,18 +332,17 @@ func (t *target) GlobalAddress() string {
 	return address
 }
 
+// BaseLabels implements Target.
 func (t *target) BaseLabels() clientmodel.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) {
+// SetBaseLabelsFrom implements Target.
+func (t *target) SetBaseLabelsFrom(newTarget Target) {
 	if t.Address() != newTarget.Address() {
 		panic("targets don't refer to the same endpoint")
 	}
-	t.baseLabels = newTarget.BaseLabels()
+	t.newBaseLabels <- newTarget.BaseLabels()
 }
 
 type targets []Target

retrieval/targetpool.go

@@ -108,7 +108,7 @@ func (p *TargetPool) ReplaceTargets(newTargets []Target) {
 		newTargetAddresses.Add(newTarget.Address())
 		oldTarget, ok := p.targetsByAddress[newTarget.Address()]
 		if ok {
-			oldTarget.Merge(newTarget)
+			oldTarget.SetBaseLabelsFrom(newTarget)
 		} else {
 			p.targetsByAddress[newTarget.Address()] = newTarget
 			go newTarget.RunScraper(p.ingester, p.interval)

storage/local/storage.go

@@ -249,8 +249,8 @@ func (s *memorySeriesStorage) Close() error {
 	stopped := make(chan bool)
 	glog.Info("Waiting for storage to stop serving...")
 	s.stopServing <- stopped
-	glog.Info("Serving stopped.")
 	<-stopped
+	glog.Info("Serving stopped.")
 
 	glog.Info("Stopping persist loop...")
 	close(s.persistQueue)
@@ -276,6 +276,7 @@ func (s *memorySeriesStorage) purgePeriodically(stop <-chan bool) {
 	for {
 		select {
 		case <-stop:
+			glog.Info("Purging loop stopped.")
 			return
 		case <-purgeTicker.C:
 			glog.Info("Purging old series data...")