Improve scraper shutdown time.

- Stop target pools in parallel.
- Stop individual scrapers in goroutines, too.
- Timing tweaks.

Change-Id: I9dff1ee18616694f14b04408eaf1625d0f989696

main.go

@@ -229,15 +229,12 @@ func (p *prometheus) Serve() {
 	if err := p.storage.Stop(); err != nil {
 		glog.Error("Error stopping local storage: ", err)
 	}
-	glog.Info("Local Storage: Done")
 
 	if p.remoteTSDBQueue != nil {
 		p.remoteTSDBQueue.Stop()
-		glog.Info("Remote Storage: Done")
 	}
 
 	p.notificationHandler.Stop()
-	glog.Info("Sundry Queues: Done")
 	glog.Info("See you next time!")
 }
 
@@ -258,9 +255,7 @@ func (p *prometheus) interruptHandler() {
 func (p *prometheus) close() {
 	glog.Info("Shutdown has been requested; subsytems are closing:")
 	p.targetManager.Stop()
-	glog.Info("Remote Target Manager: Done")
 	p.ruleManager.Stop()
-	glog.Info("Rule Executor: Done")
 
 	close(p.unwrittenSamples)
 	// Note: Before closing the remaining subsystems (storage, ...), we have

notification/notification.go

@@ -199,8 +199,10 @@ func (n *NotificationHandler) SubmitReqs(reqs NotificationReqs) {
 
 // Stop shuts down the notification handler.
 func (n *NotificationHandler) Stop() {
+	glog.Info("Stopping notification handler...")
 	close(n.pendingNotifications)
 	<-n.stopped
+	glog.Info("Notification handler stopped.")
 }
 
 // Describe implements prometheus.Collector.

retrieval/target.go

@@ -223,6 +223,7 @@ func (t *target) RunScraper(ingester extraction.Ingester, interval time.Duration
 	select {
 	case <-jitterTimer.C:
 	case <-t.stopScraper:
+		jitterTimer.Stop()
 		return
 	}
 	jitterTimer.Stop()
@@ -232,16 +233,32 @@ func (t *target) RunScraper(ingester extraction.Ingester, interval time.Duration
 
 	t.lastScrape = time.Now()
 	t.scrape(ingester)
+
+	// Explanation of the contraption below:
+	//
+	// In case t.newBaseLabels or t.stopScraper have something to receive,
+	// we want to read from those channels rather than starting a new scrape
+	// (which might take very long). That's why the outer select has no
+	// ticker.C. Should neither t.newBaseLabels nor t.stopScraper have
+	// anything to receive, we go into the inner select, where ticker.C is
+	// in the mix.
 	for {
 		select {
-		case <-ticker.C:
-			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
+		default:
+			select {
+			case newBaseLabels := <-t.newBaseLabels:
+				t.baseLabels = newBaseLabels
+			case <-t.stopScraper:
+				return
+			case <-ticker.C:
+				targetIntervalLength.WithLabelValues(interval.String()).Observe(float64(time.Since(t.lastScrape) / time.Second))
+				t.lastScrape = time.Now()
+				t.scrape(ingester)
+			}
 		}
 	}
 }

retrieval/targetmanager.go

@@ -14,6 +14,7 @@
 package retrieval
 
 import (
+	"sync"
 	"github.com/golang/glog"
 	"github.com/prometheus/client_golang/extraction"
 
@@ -105,13 +106,22 @@ func (m *targetManager) AddTargetsFromConfig(config config.Config) {
 }
 
 func (m *targetManager) Stop() {
-	glog.Info("Target manager exiting...")
+	glog.Info("Stopping target manager...")
-	for _, p := range m.poolsByJob {
+	var wg sync.WaitGroup
+	for j, p := range m.poolsByJob {
+		wg.Add(1)
+		go func(j string, p *TargetPool) {
+			defer wg.Done()
+			glog.Infof("Stopping target pool %q...", j)
 			p.Stop()
+			glog.Infof("Target pool %q stopped.", j)
+		}(j, p)
 	}
+	wg.Wait()
+	glog.Info("Target manager stopped.")
 }
 
-// TODO: Not really thread-safe. Only used in /status page for now.
+// TODO: Not goroutine-safe. Only used in /status page for now.
 func (m *targetManager) Pools() map[string]*TargetPool {
 	return m.poolsByJob
 }

retrieval/targetpool.go

@@ -71,7 +71,6 @@ func (p *TargetPool) Run() {
 			p.addTarget(newTarget)
 		case stopped := <-p.done:
 			p.ReplaceTargets([]Target{})
-			glog.Info("TargetPool exiting...")
 			close(stopped)
 			return
 		}
@@ -115,13 +114,20 @@ func (p *TargetPool) ReplaceTargets(newTargets []Target) {
 		}
 	}
 	// Stop any targets no longer present.
+	var wg sync.WaitGroup
 	for k, oldTarget := range p.targetsByAddress {
 		if !newTargetAddresses.Has(k) {
-			glog.V(1).Info("Stopping scraper for target ", k)
+			wg.Add(1)
+			go func(k string, oldTarget Target) {
+				defer wg.Done()
+				glog.V(1).Infof("Stopping scraper for target %s...", k)
 				oldTarget.StopScraper()
 				delete(p.targetsByAddress, k)
+				glog.V(1).Infof("Scraper for target %s stopped.", k)
+			}(k, oldTarget)
 		}
 	}
+	wg.Wait()
 }
 
 func (p *TargetPool) Targets() []Target {

rules/manager/manager.go

@@ -126,13 +126,14 @@ func (m *ruleManager) Run() {
 			m.runIteration(m.results)
 			iterationDuration.Observe(float64(time.Since(start) / time.Millisecond))
 		case <-m.done:
-			glog.Info("Rule manager exiting...")
+			glog.Info("Rule manager stopped.")
 			return
 		}
 	}
 }
 
 func (m *ruleManager) Stop() {
+	glog.Info("Stopping rule manager...")
 	m.done <- true
 }
 

storage/local/storage.go

@@ -181,6 +181,7 @@ func (s *memorySeriesStorage) Start() {
 
 // Stop implements Storage.
 func (s *memorySeriesStorage) Stop() error {
+	glog.Info("Stopping local storage...")
 	glog.Info("Stopping maintenance loop...")
 	close(s.loopStopping)
 	<-s.loopStopped
@@ -197,6 +198,7 @@ func (s *memorySeriesStorage) Stop() error {
 	if err := s.persistence.close(); err != nil {
 		return err
 	}
+	glog.Info("Local storage stopped.")
 	return nil
 }
 

storage/remote/queue_manager.go

@@ -122,12 +122,13 @@ func (t *TSDBQueueManager) Queue(s clientmodel.Samples) {
 // Stop stops sending samples to the TSDB and waits for pending sends to
 // complete.
 func (t *TSDBQueueManager) Stop() {
-	glog.Infof("TSDB queue manager shutting down...")
+	glog.Infof("Stopping remote storage...")
 	close(t.queue)
 	<-t.drained
 	for i := 0; i < maxConcurrentSends; i++ {
 		t.sendSemaphore <- true
 	}
+	glog.Info("Remote storage stopped.")
 }
 
 // Describe implements prometheus.Collector.