Add scraping tests

retrieval/scrape.go

@@ -74,9 +74,14 @@ type scrapePool struct {
 
 	ctx context.Context
 
+	// Targets and loops must always be synchronized to have the same
+	// set of fingerprints.
 	mtx     sync.RWMutex
 	targets map[model.Fingerprint]*Target
 	loops   map[model.Fingerprint]loop
+
+	// Constructor for new scrape loops. This is settable for testing convenience.
+	newLoop func(context.Context, scraper, storage.SampleAppender, storage.SampleAppender) loop
 }
 
 func newScrapePool(cfg *config.ScrapeConfig, app storage.SampleAppender) *scrapePool {
@@ -85,25 +90,28 @@ func newScrapePool(cfg *config.ScrapeConfig, app storage.SampleAppender) *scrape
 		config:   cfg,
 		targets:  map[model.Fingerprint]*Target{},
 		loops:    map[model.Fingerprint]loop{},
+		newLoop:  newScrapeLoop,
 	}
 }
 
 // stop terminates all scrape loops and returns after they all terminated.
-// A stopped scrape pool must not be used again.
 func (sp *scrapePool) stop() {
 	var wg sync.WaitGroup
 
-	sp.mtx.RLock()
+	sp.mtx.Lock()
+	defer sp.mtx.Unlock()
 
-	for _, l := range sp.loops {
+	for fp, l := range sp.loops {
 		wg.Add(1)
 
 		go func(l loop) {
 			l.stop()
 			wg.Done()
 		}(l)
+
+		delete(sp.loops, fp)
+		delete(sp.targets, fp)
 	}
-	sp.mtx.RUnlock()
 
 	wg.Wait()
 }
@@ -126,7 +134,7 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) {
 	for fp, oldLoop := range sp.loops {
 		var (
 			t       = sp.targets[fp]
-			newLoop = newScrapeLoop(sp.ctx, t, sp.sampleAppender(t), sp.reportAppender(t))
+			newLoop = sp.newLoop(sp.ctx, t, sp.sampleAppender(t), sp.reportAppender(t))
 		)
 		wg.Add(1)
 
@@ -143,6 +151,56 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) {
 	wg.Wait()
 }
 
+// sync takes a list of potentially duplicated targets, deduplicates them, starts
+// scrape loops for new targets, and stops scrape loops for disappeared targets.
+// It returns after all stopped scrape loops terminated.
+func (sp *scrapePool) sync(targets []*Target) {
+	sp.mtx.Lock()
+	defer sp.mtx.Unlock()
+
+	var (
+		fingerprints = map[model.Fingerprint]struct{}{}
+		interval     = time.Duration(sp.config.ScrapeInterval)
+		timeout      = time.Duration(sp.config.ScrapeTimeout)
+	)
+
+	for _, t := range targets {
+		fp := t.fingerprint()
+		fingerprints[fp] = struct{}{}
+
+		if _, ok := sp.targets[fp]; !ok {
+			l := sp.newLoop(sp.ctx, t, sp.sampleAppender(t), sp.reportAppender(t))
+
+			sp.targets[fp] = t
+			sp.loops[fp] = l
+
+			go l.run(interval, timeout, nil)
+		}
+	}
+
+	var wg sync.WaitGroup
+
+	// Stop and remove old targets and scraper loops.
+	for fp := range sp.targets {
+		if _, ok := fingerprints[fp]; !ok {
+			wg.Add(1)
+			go func(l loop) {
+				l.stop()
+				wg.Done()
+			}(sp.loops[fp])
+
+			delete(sp.loops, fp)
+			delete(sp.targets, fp)
+		}
+	}
+
+	// Wait for all potentially stopped scrapers to terminate.
+	// This covers the case of flapping targets. If the server is under high load, a new scraper
+	// may be active and tries to insert. The old scraper that didn't terminate yet could still
+	// be inserting a previous sample set.
+	wg.Wait()
+}
+
 // sampleAppender returns an appender for ingested samples from the target.
 func (sp *scrapePool) sampleAppender(target *Target) storage.SampleAppender {
 	app := sp.appender
@@ -177,56 +235,6 @@ func (sp *scrapePool) reportAppender(target *Target) storage.SampleAppender {
 	}
 }
 
-// sync takes a list of potentially duplicated targets, deduplicates them, starts
-// scrape loops for new targets, and stops scrape loops for disappeared targets.
-// It returns after all stopped scrape loops terminated.
-func (sp *scrapePool) sync(targets []*Target) {
-	sp.mtx.Lock()
-	defer sp.mtx.Unlock()
-
-	var (
-		fingerprints = map[model.Fingerprint]struct{}{}
-		interval     = time.Duration(sp.config.ScrapeInterval)
-		timeout      = time.Duration(sp.config.ScrapeTimeout)
-	)
-
-	for _, t := range targets {
-		fp := t.fingerprint()
-		fingerprints[fp] = struct{}{}
-
-		if _, ok := sp.targets[fp]; !ok {
-			l := newScrapeLoop(sp.ctx, t, sp.sampleAppender(t), sp.reportAppender(t))
-
-			sp.targets[fp] = t
-			sp.loops[fp] = l
-
-			go l.run(interval, timeout, nil)
-		}
-	}
-
-	var wg sync.WaitGroup
-
-	// Stop and remove old targets and scraper loops.
-	for fp := range sp.targets {
-		if _, ok := fingerprints[fp]; !ok {
-			wg.Add(1)
-			go func(l loop) {
-				l.stop()
-				wg.Done()
-			}(sp.loops[fp])
-
-			delete(sp.loops, fp)
-			delete(sp.targets, fp)
-		}
-	}
-
-	// Wait for all potentially stopped scrapers to terminate.
-	// This covers the case of flapping targets. If the server is under high load, a new scraper
-	// may be active and tries to insert. The old scraper that didn't terminate yet could still
-	// be inserting a previous sample set.
-	wg.Wait()
-}
-
 // A scraper retrieves samples and accepts a status report at the end.
 type scraper interface {
 	scrape(ctx context.Context, ts time.Time) (model.Samples, error)
@@ -234,7 +242,7 @@ type scraper interface {
 	offset(interval time.Duration) time.Duration
 }
 
-// A loop can run and be stopped again. It must be reused after it was stopped.
+// A loop can run and be stopped again. It must not be reused after it was stopped.
 type loop interface {
 	run(interval, timeout time.Duration, errc chan<- error)
 	stop()
@@ -247,12 +255,11 @@ type scrapeLoop struct {
 	reportAppender storage.SampleAppender
 
 	done   chan struct{}
-	mtx    sync.RWMutex
 	ctx    context.Context
 	cancel func()
 }
 
-func newScrapeLoop(ctx context.Context, sc scraper, app, reportApp storage.SampleAppender) *scrapeLoop {
+func newScrapeLoop(ctx context.Context, sc scraper, app, reportApp storage.SampleAppender) loop {
 	sl := &scrapeLoop{
 		scraper:        sc,
 		appender:       app,
@@ -321,10 +328,7 @@ func (sl *scrapeLoop) run(interval, timeout time.Duration, errc chan<- error) {
 }
 
 func (sl *scrapeLoop) stop() {
-	sl.mtx.RLock()
 	sl.cancel()
-	sl.mtx.RUnlock()
-
 	<-sl.done
 }
 

retrieval/scrape_test.go

@@ -14,6 +14,9 @@
 package retrieval
 
 import (
+	"fmt"
+	"reflect"
+	"sync"
 	"testing"
 	"time"
 
@@ -21,8 +24,199 @@ import (
 	"golang.org/x/net/context"
 
 	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/storage"
 )
 
+func TestNewScrapePool(t *testing.T) {
+	var (
+		app = &nopAppender{}
+		cfg = &config.ScrapeConfig{}
+		sp  = newScrapePool(cfg, app)
+	)
+
+	if a, ok := sp.appender.(*nopAppender); !ok || a != app {
+		t.Fatalf("Wrong sample appender")
+	}
+	if sp.config != cfg {
+		t.Fatalf("Wrong scrape config")
+	}
+	if sp.newLoop == nil {
+		t.Fatalf("newLoop function not initialized")
+	}
+}
+
+type testLoop struct {
+	startFunc func(interval, timeout time.Duration, errc chan<- error)
+	stopFunc  func()
+}
+
+func (l *testLoop) run(interval, timeout time.Duration, errc chan<- error) {
+	l.startFunc(interval, timeout, errc)
+}
+
+func (l *testLoop) stop() {
+	l.stopFunc()
+}
+
+func TestScrapePoolStop(t *testing.T) {
+	sp := &scrapePool{
+		targets: map[model.Fingerprint]*Target{},
+		loops:   map[model.Fingerprint]loop{},
+	}
+	var mtx sync.Mutex
+	stopped := map[model.Fingerprint]bool{}
+	numTargets := 20
+
+	// Stopping the scrape pool must call stop() on all scrape loops,
+	// clean them and the respective targets up. It must wait until each loop's
+	// stop function returned before returning itself.
+
+	for i := 0; i < numTargets; i++ {
+		t := &Target{
+			labels: model.LabelSet{
+				model.AddressLabel: model.LabelValue(fmt.Sprintf("example.com:%d", i)),
+			},
+		}
+		l := &testLoop{}
+		l.stopFunc = func() {
+			time.Sleep(time.Duration(i*20) * time.Millisecond)
+
+			mtx.Lock()
+			stopped[t.fingerprint()] = true
+			mtx.Unlock()
+		}
+
+		sp.targets[t.fingerprint()] = t
+		sp.loops[t.fingerprint()] = l
+	}
+
+	done := make(chan struct{})
+	stopTime := time.Now()
+
+	go func() {
+		sp.stop()
+		close(done)
+	}()
+
+	select {
+	case <-time.After(5 * time.Second):
+		t.Fatalf("scrapeLoop.stop() did not return as expected")
+	case <-done:
+		// This should have taken at least as long as the last target slept.
+		if time.Since(stopTime) < time.Duration(numTargets*20)*time.Millisecond {
+			t.Fatalf("scrapeLoop.stop() exited before all targets stopped")
+		}
+	}
+
+	mtx.Lock()
+	if len(stopped) != numTargets {
+		t.Fatalf("Expected 20 stopped loops, got %d", len(stopped))
+	}
+	mtx.Unlock()
+
+	if len(sp.targets) > 0 {
+		t.Fatalf("Targets were not cleared on stopping: %d left", len(sp.targets))
+	}
+	if len(sp.loops) > 0 {
+		t.Fatalf("Loops were not cleared on stopping: %d left", len(sp.loops))
+	}
+}
+
+func TestScrapePoolReload(t *testing.T) {
+	var mtx sync.Mutex
+	numTargets := 20
+
+	stopped := map[model.Fingerprint]bool{}
+
+	reloadCfg := &config.ScrapeConfig{
+		ScrapeInterval: model.Duration(3 * time.Second),
+		ScrapeTimeout:  model.Duration(2 * time.Second),
+	}
+	// On starting to run, new loops created on reload check whether their preceeding
+	// equivalents have been stopped.
+	newLoop := func(ctx context.Context, s scraper, app, reportApp storage.SampleAppender) loop {
+		l := &testLoop{}
+		l.startFunc = func(interval, timeout time.Duration, errc chan<- error) {
+			if interval != 3*time.Second {
+				t.Errorf("Expected scrape interval %d but got %d", 3*time.Second, interval)
+			}
+			if timeout != 2*time.Second {
+				t.Errorf("Expected scrape timeout %d but got %d", 2*time.Second, timeout)
+			}
+			mtx.Lock()
+			if !stopped[s.(*Target).fingerprint()] {
+				t.Errorf("Scrape loop for %v not stopped yet", s.(*Target))
+			}
+			mtx.Unlock()
+		}
+		return l
+	}
+	sp := &scrapePool{
+		targets: map[model.Fingerprint]*Target{},
+		loops:   map[model.Fingerprint]loop{},
+		newLoop: newLoop,
+	}
+
+	// Reloading a scrape pool with a new scrape configuration must stop all scrape
+	// loops and start new ones. A new loop must not be started before the preceeding
+	// one terminated.
+
+	for i := 0; i < numTargets; i++ {
+		t := &Target{
+			labels: model.LabelSet{
+				model.AddressLabel: model.LabelValue(fmt.Sprintf("example.com:%d", i)),
+			},
+		}
+		l := &testLoop{}
+		l.stopFunc = func() {
+			time.Sleep(time.Duration(i*20) * time.Millisecond)
+
+			mtx.Lock()
+			stopped[t.fingerprint()] = true
+			mtx.Unlock()
+		}
+
+		sp.targets[t.fingerprint()] = t
+		sp.loops[t.fingerprint()] = l
+	}
+	done := make(chan struct{})
+
+	beforeTargets := map[model.Fingerprint]*Target{}
+	for fp, t := range sp.targets {
+		beforeTargets[fp] = t
+	}
+
+	reloadTime := time.Now()
+
+	go func() {
+		sp.reload(reloadCfg)
+		close(done)
+	}()
+
+	select {
+	case <-time.After(5 * time.Second):
+		t.Fatalf("scrapeLoop.reload() did not return as expected")
+	case <-done:
+		// This should have taken at least as long as the last target slept.
+		if time.Since(reloadTime) < time.Duration(numTargets*20)*time.Millisecond {
+			t.Fatalf("scrapeLoop.stop() exited before all targets stopped")
+		}
+	}
+
+	mtx.Lock()
+	if len(stopped) != numTargets {
+		t.Fatalf("Expected 20 stopped loops, got %d", stopped)
+	}
+	mtx.Unlock()
+
+	if !reflect.DeepEqual(sp.targets, beforeTargets) {
+		t.Fatalf("Reloading affected target states unexpectedly")
+	}
+	if len(sp.loops) != numTargets {
+		t.Fatalf("Expected %d loops after reload but got %d", numTargets, len(sp.loops))
+	}
+}
+
 func TestScrapePoolReportAppender(t *testing.T) {
 	cfg := &config.ScrapeConfig{
 		MetricRelabelConfigs: []*config.RelabelConfig{
@@ -100,6 +294,53 @@ func TestScrapePoolSampleAppender(t *testing.T) {
 	}
 }
 
+func TestScrapeLoopStop(t *testing.T) {
+	scraper := &testScraper{}
+	sl := newScrapeLoop(context.Background(), scraper, nil, nil)
+
+	// The scrape pool synchronizes on stopping scrape loops. However, new scrape
+	// loops are syarted asynchronously. Thus it's possible, that a loop is stopped
+	// again before having started properly.
+	// Stopping not-yet-started loops must block until the run method was called and exited.
+	// The run method must exit immediately.
+
+	stopDone := make(chan struct{})
+	go func() {
+		sl.stop()
+		close(stopDone)
+	}()
+
+	select {
+	case <-stopDone:
+		t.Fatalf("Stopping terminated before run exited successfully")
+	case <-time.After(500 * time.Millisecond):
+	}
+
+	// Running the scrape loop must exit before calling the scraper even once.
+	scraper.scrapeFunc = func(context.Context, time.Time) (model.Samples, error) {
+		t.Fatalf("scraper was called for terminated scrape loop")
+		return nil, nil
+	}
+
+	runDone := make(chan struct{})
+	go func() {
+		sl.run(0, 0, nil)
+		close(runDone)
+	}()
+
+	select {
+	case <-runDone:
+	case <-time.After(1 * time.Second):
+		t.Fatalf("Running terminated scrape loop did not exit")
+	}
+
+	select {
+	case <-stopDone:
+	case <-time.After(1 * time.Second):
+		t.Fatalf("Stopping did not terminate after running exited")
+	}
+}
+
 func TestScrapeLoopRun(t *testing.T) {
 	var (
 		signal = make(chan struct{})