From 50c81bed86327fa4c954d5cab35142f84bfce532 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C5=81ukasz=20Mierzwa?= Date: Thu, 16 Nov 2023 13:22:28 +0000 Subject: [PATCH] Check for duplicated series on a scrape MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When Prometheus scrapes a target and it sees the same time series repeated multiple times it currently silently ignores that. This change adds a test for that and fixes the scrape loop so that: - Only first sample for each unique time series is appended - Duplicated samples increment the prometheus_target_scrapes_sample_duplicate_timestamp_total metric This allows one to identify such scrape jobs and targets. Benchmark results: ``` name old time/op new time/op delta ScrapeLoopAppend-8 64.8µs ± 2% 71.1µs ±20% +9.75% (p=0.000 n=10+10) ScrapeLoopAppendOM-8 64.2µs ± 1% 68.5µs ± 7% +6.71% (p=0.000 n=9+10) TargetsFromGroup/1_targets-8 14.2µs ± 1% 14.5µs ± 1% +1.99% (p=0.000 n=10+10) TargetsFromGroup/10_targets-8 149µs ± 1% 152µs ± 1% +2.05% (p=0.000 n=9+10) TargetsFromGroup/100_targets-8 1.49ms ± 4% 1.48ms ± 1% ~ (p=0.796 n=10+10) name old alloc/op new alloc/op delta ScrapeLoopAppend-8 19.9kB ± 1% 17.8kB ± 3% -10.23% (p=0.000 n=8+10) ScrapeLoopAppendOM-8 19.9kB ± 1% 18.3kB ±10% -8.14% (p=0.001 n=9+10) TargetsFromGroup/1_targets-8 2.43kB ± 0% 2.43kB ± 0% -0.15% (p=0.045 n=10+10) TargetsFromGroup/10_targets-8 24.3kB ± 0% 24.3kB ± 0% ~ (p=0.083 n=10+9) TargetsFromGroup/100_targets-8 243kB ± 0% 243kB ± 0% ~ (p=0.720 n=9+10) name old allocs/op new allocs/op delta ScrapeLoopAppend-8 9.00 ± 0% 9.00 ± 0% ~ (all equal) ScrapeLoopAppendOM-8 10.0 ± 0% 10.0 ± 0% ~ (all equal) TargetsFromGroup/1_targets-8 40.0 ± 0% 40.0 ± 0% ~ (all equal) TargetsFromGroup/10_targets-8 400 ± 0% 400 ± 0% ~ (all equal) TargetsFromGroup/100_targets-8 4.00k ± 0% 4.00k ± 0% ~ (all equal) ``` Signed-off-by: Łukasz Mierzwa --- scrape/scrape.go | 49 +++++++++++++++++++++++++------------------ scrape/scrape_test.go | 28 +++++++++++++++++++++++++ 2 files changed, 57 insertions(+), 20 deletions(-) diff --git a/scrape/scrape.go b/scrape/scrape.go index aa2d5538b..9bff47eeb 100644 --- a/scrape/scrape.go +++ b/scrape/scrape.go @@ -1512,13 +1512,13 @@ func (sl *scrapeLoop) append(app storage.Appender, b []byte, contentType string, loop: for { var ( - et textparse.Entry - sampleAdded, isHistogram bool - met []byte - parsedTimestamp *int64 - val float64 - h *histogram.Histogram - fh *histogram.FloatHistogram + et textparse.Entry + sampleAdded, isHistogram, seriesAlreadyScraped bool + met []byte + parsedTimestamp *int64 + val float64 + h *histogram.Histogram + fh *histogram.FloatHistogram ) if et, err = p.Next(); err != nil { if errors.Is(err, io.EOF) { @@ -1573,6 +1573,7 @@ loop: if ok { ref = ce.ref lset = ce.lset + hash = ce.hash // Update metadata only if it changed in the current iteration. updateMetadata(lset, false) @@ -1609,24 +1610,30 @@ loop: updateMetadata(lset, true) } - if ctMs := p.CreatedTimestamp(); sl.enableCTZeroIngestion && ctMs != nil { - ref, err = app.AppendCTZeroSample(ref, lset, t, *ctMs) - if err != nil && !errors.Is(err, storage.ErrOutOfOrderCT) { // OOO is a common case, ignoring completely for now. - // CT is an experimental feature. For now, we don't need to fail the - // scrape on errors updating the created timestamp, log debug. - level.Debug(sl.l).Log("msg", "Error when appending CT in scrape loop", "series", string(met), "ct", *ctMs, "t", t, "err", err) + _, seriesAlreadyScraped = sl.cache.seriesCur[hash] + if seriesAlreadyScraped { + err = storage.ErrDuplicateSampleForTimestamp + } else { + if ctMs := p.CreatedTimestamp(); sl.enableCTZeroIngestion && ctMs != nil { + ref, err = app.AppendCTZeroSample(ref, lset, t, *ctMs) + if err != nil && !errors.Is(err, storage.ErrOutOfOrderCT) { // OOO is a common case, ignoring completely for now. + // CT is an experimental feature. For now, we don't need to fail the + // scrape on errors updating the created timestamp, log debug. + level.Debug(sl.l).Log("msg", "Error when appending CT in scrape loop", "series", string(met), "ct", *ctMs, "t", t, "err", err) + } } - } - if isHistogram { - if h != nil { - ref, err = app.AppendHistogram(ref, lset, t, h, nil) + if isHistogram { + if h != nil { + ref, err = app.AppendHistogram(ref, lset, t, h, nil) + } else { + ref, err = app.AppendHistogram(ref, lset, t, nil, fh) + } } else { - ref, err = app.AppendHistogram(ref, lset, t, nil, fh) + ref, err = app.Append(ref, lset, t, val) } - } else { - ref, err = app.Append(ref, lset, t, val) } + sampleAdded, err = sl.checkAddError(ce, met, parsedTimestamp, err, &sampleLimitErr, &bucketLimitErr, &appErrs) if err != nil { if !errors.Is(err, storage.ErrNotFound) { @@ -1648,6 +1655,8 @@ loop: // Increment added even if there's an error so we correctly report the // number of samples remaining after relabeling. + // We still report duplicated samples here since this number should be the exact number + // of time series exposed on a scrape after relabelling. added++ exemplars = exemplars[:0] // Reset and reuse the exemplar slice. for hasExemplar := p.Exemplar(&e); hasExemplar; hasExemplar = p.Exemplar(&e) { diff --git a/scrape/scrape_test.go b/scrape/scrape_test.go index e37d091ae..4732fbe0d 100644 --- a/scrape/scrape_test.go +++ b/scrape/scrape_test.go @@ -3600,3 +3600,31 @@ func BenchmarkTargetScraperGzip(b *testing.B) { }) } } + +// When a scrape contains multiple instances for the same time series we should increment +// prometheus_target_scrapes_sample_duplicate_timestamp_total metric. +func TestScrapeLoopSeriesAddedDuplicates(t *testing.T) { + ctx, sl := simpleTestScrapeLoop(t) + + slApp := sl.appender(ctx) + total, added, seriesAdded, err := sl.append(slApp, []byte("test_metric 1\ntest_metric 2\ntest_metric 3\n"), "", time.Time{}) + require.NoError(t, err) + require.NoError(t, slApp.Commit()) + require.Equal(t, 3, total) + require.Equal(t, 3, added) + require.Equal(t, 1, seriesAdded) + + slApp = sl.appender(ctx) + total, added, seriesAdded, err = sl.append(slApp, []byte("test_metric 1\ntest_metric 1\ntest_metric 1\n"), "", time.Time{}) + require.NoError(t, err) + require.NoError(t, slApp.Commit()) + require.Equal(t, 3, total) + require.Equal(t, 3, added) + require.Equal(t, 0, seriesAdded) + + metric := dto.Metric{} + err = sl.metrics.targetScrapeSampleDuplicate.Write(&metric) + require.NoError(t, err) + value := metric.GetCounter().GetValue() + require.Equal(t, 4.0, value) +}