From d532272520610c0e8fcb6ae83c90411f9873b08b Mon Sep 17 00:00:00 2001
From: Brian Brazil <brian.brazil@robustperception.io>
Date: Thu, 11 May 2017 14:43:43 +0100
Subject: [PATCH] Add stalemarkers to synthetic series too when target stops.

---
 retrieval/helpers_test.go |  2 +-
 retrieval/scrape.go       | 50 ++++++++++++++++++++++++++++++++++-----
 retrieval/scrape_test.go  | 17 ++++++++++++-
 3 files changed, 61 insertions(+), 8 deletions(-)

diff --git a/retrieval/helpers_test.go b/retrieval/helpers_test.go
index 32f5cb68f..5ce761c8c 100644
--- a/retrieval/helpers_test.go
+++ b/retrieval/helpers_test.go
@@ -38,7 +38,7 @@ type collectResultAppender struct {
 
 func (a *collectResultAppender) AddFast(ref uint64, t int64, v float64) error {
 	// Not implemented.
-	return nil
+	return storage.ErrNotFound
 }
 
 func (a *collectResultAppender) Add(m labels.Labels, t int64, v float64) (uint64, error) {
diff --git a/retrieval/scrape.go b/retrieval/scrape.go
index 6d097d55c..3e5e41db3 100644
--- a/retrieval/scrape.go
+++ b/retrieval/scrape.go
@@ -566,6 +566,9 @@ mainLoop:
 	if _, _, err := sl.append([]byte{}, staleTime); err != nil {
 		log.With("err", err).Error("stale append failed")
 	}
+	if err := sl.reportStale(staleTime); err != nil {
+		log.With("err", err).Error("stale report failed")
+	}
 }
 
 // Stop the scraping. May still write data and stale markers after it has
@@ -738,13 +741,45 @@ func (sl *scrapeLoop) report(start time.Time, duration time.Duration, scraped, a
 	return app.Commit()
 }
 
+func (sl *scrapeLoop) reportStale(start time.Time) error {
+	ts := timestamp.FromTime(start)
+	app := sl.reportAppender()
+	stale := math.Float64frombits(value.StaleNaN)
+
+	if err := sl.addReportSample(app, scrapeHealthMetricName, ts, stale); err != nil {
+		app.Rollback()
+		return err
+	}
+	if err := sl.addReportSample(app, scrapeDurationMetricName, ts, stale); err != nil {
+		app.Rollback()
+		return err
+	}
+	if err := sl.addReportSample(app, scrapeSamplesMetricName, ts, stale); err != nil {
+		app.Rollback()
+		return err
+	}
+	if err := sl.addReportSample(app, samplesPostRelabelMetricName, ts, stale); err != nil {
+		app.Rollback()
+		return err
+	}
+	return app.Commit()
+}
+
 func (sl *scrapeLoop) addReportSample(app storage.Appender, s string, t int64, v float64) error {
 	ref, ok := sl.refCache[s]
 
 	if ok {
-		if err := app.AddFast(ref, t, v); err == nil {
+		err := app.AddFast(ref, t, v)
+		switch err {
+		case nil:
 			return nil
-		} else if err != storage.ErrNotFound {
+		case storage.ErrNotFound:
+			// Try an Add.
+		case storage.ErrOutOfOrderSample, storage.ErrDuplicateSampleForTimestamp:
+			// Do not log here, as this is expected if a target goes away and comes back
+			// again with a new scrape loop.
+			return nil
+		default:
 			return err
 		}
 	}
@@ -752,10 +787,13 @@ func (sl *scrapeLoop) addReportSample(app storage.Appender, s string, t int64, v
 		labels.Label{Name: labels.MetricName, Value: s},
 	}
 	ref, err := app.Add(met, t, v)
-	if err != nil {
+	switch err {
+	case nil:
+		sl.refCache[s] = ref
+		return nil
+	case storage.ErrOutOfOrderSample, storage.ErrDuplicateSampleForTimestamp:
+		return nil
+	default:
 		return err
 	}
-	sl.refCache[s] = ref
-
-	return nil
 }
diff --git a/retrieval/scrape_test.go b/retrieval/scrape_test.go
index 2477eaf25..878995f57 100644
--- a/retrieval/scrape_test.go
+++ b/retrieval/scrape_test.go
@@ -357,12 +357,13 @@ func TestScrapeLoopStopBeforeRun(t *testing.T) {
 
 func TestScrapeLoopStop(t *testing.T) {
 	appender := &collectResultAppender{}
+	reportAppender := &collectResultAppender{}
 	var (
 		signal = make(chan struct{})
 
 		scraper    = &testScraper{}
 		app        = func() storage.Appender { return appender }
-		reportApp  = func() storage.Appender { return &nopAppender{} }
+		reportApp  = func() storage.Appender { return reportAppender }
 		numScrapes = 0
 	)
 	defer close(signal)
@@ -398,6 +399,20 @@ func TestScrapeLoopStop(t *testing.T) {
 	if !value.IsStaleNaN(appender.result[len(appender.result)-1].v) {
 		t.Fatalf("Appended last sample not as expected. Wanted: stale NaN Got: %x", math.Float64bits(appender.result[len(appender.result)].v))
 	}
+
+	if len(reportAppender.result) < 8 {
+		t.Fatalf("Appended samples not as expected. Wanted: at least %d samples Got: %d", 8, len(reportAppender.result))
+	}
+	if len(reportAppender.result)%4 != 0 {
+		t.Fatalf("Appended samples not as expected. Wanted: samples mod 4 == 0 Got: %d samples", len(reportAppender.result))
+	}
+	if !value.IsStaleNaN(reportAppender.result[len(reportAppender.result)-1].v) {
+		t.Fatalf("Appended last sample not as expected. Wanted: stale NaN Got: %x", math.Float64bits(reportAppender.result[len(reportAppender.result)].v))
+	}
+
+	if reportAppender.result[len(reportAppender.result)-1].t != appender.result[len(appender.result)-1].t {
+		t.Fatalf("Expected last append and report sample to have same timestamp. Append: stale NaN Report: %x", appender.result[len(appender.result)-1].t, reportAppender.result[len(reportAppender.result)-1].t)
+	}
 }
 
 func TestScrapeLoopRun(t *testing.T) {