Drop old inmemory samples

config/config.go

@@ -1124,6 +1124,9 @@ type QueueConfig struct {
 	MinBackoff       model.Duration `yaml:"min_backoff,omitempty"`
 	MaxBackoff       model.Duration `yaml:"max_backoff,omitempty"`
 	RetryOnRateLimit bool           `yaml:"retry_on_http_429,omitempty"`
+
+	// Samples older than the limit will be dropped.
+	SampleAgeLimit model.Duration `yaml:"sample_age_limit,omitempty"`
 }
 
 // MetadataConfig is the configuration for sending metadata to remote

docs/configuration/configuration.md

@@ -3619,6 +3619,10 @@ queue_config:
   # Retry upon receiving a 429 status code from the remote-write storage.
   # This is experimental and might change in the future.
   [ retry_on_http_429: <boolean> | default = false ]
+  # If set, any sample that is older than sample_age_limit
+  # will not be sent to the remote storage. The default value is 0s,
+  # which means that all samples are sent.
+  [ sample_age_limit: <duration> | default = 0s ]
 
 # Configures the sending of series metadata to remote storage.
 # Metadata configuration is subject to change at any point

storage/remote/codec_test.go

@@ -517,7 +517,7 @@ func TestMetricTypeToMetricTypeProto(t *testing.T) {
 }
 
 func TestDecodeWriteRequest(t *testing.T) {
-	buf, _, err := buildWriteRequest(writeRequestFixture.Timeseries, nil, nil, nil)
+	buf, _, _, err := buildWriteRequest(nil, writeRequestFixture.Timeseries, nil, nil, nil, nil)
 	require.NoError(t, err)
 
 	actual, err := DecodeWriteRequest(bytes.NewReader(buf))

storage/remote/queue_manager.go

@@ -36,6 +36,7 @@ import (
 	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/relabel"
+	"github.com/prometheus/prometheus/model/timestamp"
 	"github.com/prometheus/prometheus/prompb"
 	"github.com/prometheus/prometheus/scrape"
 	"github.com/prometheus/prometheus/tsdb/chunks"
@@ -51,6 +52,10 @@ const (
 
 	// Allow 30% too many shards before scaling down.
 	shardToleranceFraction = 0.3
+
+	reasonTooOld                     = "too_old"
+	reasonDroppedSeries              = "dropped_series"
+	reasonUnintentionalDroppedSeries = "unintentionally_dropped_series"
 )
 
 type queueManagerMetrics struct {
@@ -68,9 +73,9 @@ type queueManagerMetrics struct {
 	retriedExemplarsTotal  prometheus.Counter
 	retriedHistogramsTotal prometheus.Counter
 	retriedMetadataTotal   prometheus.Counter
-	droppedSamplesTotal    prometheus.Counter
-	droppedExemplarsTotal  prometheus.Counter
-	droppedHistogramsTotal prometheus.Counter
+	droppedSamplesTotal    *prometheus.CounterVec
+	droppedExemplarsTotal  *prometheus.CounterVec
+	droppedHistogramsTotal *prometheus.CounterVec
 	enqueueRetriesTotal    prometheus.Counter
 	sentBatchDuration      prometheus.Histogram
 	highestSentTimestamp   *maxTimestamp
@@ -180,27 +185,27 @@ func newQueueManagerMetrics(r prometheus.Registerer, rn, e string) *queueManager
 		Help:        "Total number of metadata entries which failed on send to remote storage but were retried because the send error was recoverable.",
 		ConstLabels: constLabels,
 	})
-	m.droppedSamplesTotal = prometheus.NewCounter(prometheus.CounterOpts{
+	m.droppedSamplesTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
 		Namespace:   namespace,
 		Subsystem:   subsystem,
 		Name:        "samples_dropped_total",
-		Help:        "Total number of samples which were dropped after being read from the WAL before being sent via remote write, either via relabelling or unintentionally because of an unknown reference ID.",
+		Help:        "Total number of samples which were dropped after being read from the WAL before being sent via remote write, either via relabelling, due to being too old or unintentionally because of an unknown reference ID.",
 		ConstLabels: constLabels,
-	})
-	m.droppedExemplarsTotal = prometheus.NewCounter(prometheus.CounterOpts{
+	}, []string{"reason"})
+	m.droppedExemplarsTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
 		Namespace:   namespace,
 		Subsystem:   subsystem,
 		Name:        "exemplars_dropped_total",
-		Help:        "Total number of exemplars which were dropped after being read from the WAL before being sent via remote write, either via relabelling or unintentionally because of an unknown reference ID.",
+		Help:        "Total number of exemplars which were dropped after being read from the WAL before being sent via remote write, either via relabelling, due to being too old or unintentionally because of an unknown reference ID.",
 		ConstLabels: constLabels,
-	})
-	m.droppedHistogramsTotal = prometheus.NewCounter(prometheus.CounterOpts{
+	}, []string{"reason"})
+	m.droppedHistogramsTotal = prometheus.NewCounterVec(prometheus.CounterOpts{
 		Namespace:   namespace,
 		Subsystem:   subsystem,
 		Name:        "histograms_dropped_total",
-		Help:        "Total number of histograms which were dropped after being read from the WAL before being sent via remote write, either via relabelling or unintentionally because of an unknown reference ID.",
+		Help:        "Total number of histograms which were dropped after being read from the WAL before being sent via remote write, either via relabelling, due to being too old or unintentionally because of an unknown reference ID.",
 		ConstLabels: constLabels,
-	})
+	}, []string{"reason"})
 	m.enqueueRetriesTotal = prometheus.NewCounter(prometheus.CounterOpts{
 		Namespace:   namespace,
 		Subsystem:   subsystem,
@@ -391,7 +396,8 @@ type WriteClient interface {
 // indicated by the provided WriteClient. Implements writeTo interface
 // used by WAL Watcher.
 type QueueManager struct {
-	lastSendTimestamp atomic.Int64
+	lastSendTimestamp          atomic.Int64
+	buildRequestLimitTimestamp atomic.Int64
 
 	logger               log.Logger
 	flushDeadline        time.Duration
@@ -529,7 +535,7 @@ func (t *QueueManager) AppendMetadata(ctx context.Context, metadata []scrape.Met
 
 func (t *QueueManager) sendMetadataWithBackoff(ctx context.Context, metadata []prompb.MetricMetadata, pBuf *proto.Buffer) error {
 	// Build the WriteRequest with no samples.
-	req, _, err := buildWriteRequest(nil, metadata, pBuf, nil)
+	req, _, _, err := buildWriteRequest(t.logger, nil, metadata, pBuf, nil, nil)
 	if err != nil {
 		return err
 	}
@@ -575,18 +581,65 @@ func (t *QueueManager) sendMetadataWithBackoff(ctx context.Context, metadata []p
 	return nil
 }
 
+func isSampleOld(baseTime time.Time, sampleAgeLimit time.Duration, ts int64) bool {
+	if sampleAgeLimit == 0 {
+		// If sampleAgeLimit is unset, then we never skip samples due to their age.
+		return false
+	}
+	limitTs := baseTime.Add(-sampleAgeLimit)
+	sampleTs := timestamp.Time(ts)
+	return sampleTs.Before(limitTs)
+}
+
+func isTimeSeriesOldFilter(metrics *queueManagerMetrics, baseTime time.Time, sampleAgeLimit time.Duration) func(ts prompb.TimeSeries) bool {
+	return func(ts prompb.TimeSeries) bool {
+		if sampleAgeLimit == 0 {
+			// If sampleAgeLimit is unset, then we never skip samples due to their age.
+			return false
+		}
+		switch {
+		// Only the first element should be set in the series, therefore we only check the first element.
+		case len(ts.Samples) > 0:
+			if isSampleOld(baseTime, sampleAgeLimit, ts.Samples[0].Timestamp) {
+				metrics.droppedSamplesTotal.WithLabelValues(reasonTooOld).Inc()
+				return true
+			}
+		case len(ts.Histograms) > 0:
+			if isSampleOld(baseTime, sampleAgeLimit, ts.Histograms[0].Timestamp) {
+				metrics.droppedHistogramsTotal.WithLabelValues(reasonTooOld).Inc()
+				return true
+			}
+		case len(ts.Exemplars) > 0:
+			if isSampleOld(baseTime, sampleAgeLimit, ts.Exemplars[0].Timestamp) {
+				metrics.droppedExemplarsTotal.WithLabelValues(reasonTooOld).Inc()
+				return true
+			}
+		default:
+			return false
+		}
+		return false
+	}
+}
+
 // Append queues a sample to be sent to the remote storage. Blocks until all samples are
 // enqueued on their shards or a shutdown signal is received.
 func (t *QueueManager) Append(samples []record.RefSample) bool {
+	currentTime := time.Now()
 outer:
 	for _, s := range samples {
+		if isSampleOld(currentTime, time.Duration(t.cfg.SampleAgeLimit), s.T) {
+			t.metrics.droppedSamplesTotal.WithLabelValues(reasonTooOld).Inc()
+			continue
+		}
 		t.seriesMtx.Lock()
 		lbls, ok := t.seriesLabels[s.Ref]
 		if !ok {
-			t.metrics.droppedSamplesTotal.Inc()
 			t.dataDropped.incr(1)
 			if _, ok := t.droppedSeries[s.Ref]; !ok {
 				level.Info(t.logger).Log("msg", "Dropped sample for series that was not explicitly dropped via relabelling", "ref", s.Ref)
+				t.metrics.droppedSamplesTotal.WithLabelValues(reasonUnintentionalDroppedSeries).Inc()
+			} else {
+				t.metrics.droppedSamplesTotal.WithLabelValues(reasonDroppedSeries).Inc()
 			}
 			t.seriesMtx.Unlock()
 			continue
@@ -629,17 +682,23 @@ func (t *QueueManager) AppendExemplars(exemplars []record.RefExemplar) bool {
 	if !t.sendExemplars {
 		return true
 	}
-
+	currentTime := time.Now()
 outer:
 	for _, e := range exemplars {
+		if isSampleOld(currentTime, time.Duration(t.cfg.SampleAgeLimit), e.T) {
+			t.metrics.droppedExemplarsTotal.WithLabelValues(reasonTooOld).Inc()
+			continue
+		}
 		t.seriesMtx.Lock()
 		lbls, ok := t.seriesLabels[e.Ref]
 		if !ok {
-			t.metrics.droppedExemplarsTotal.Inc()
 			// Track dropped exemplars in the same EWMA for sharding calc.
 			t.dataDropped.incr(1)
 			if _, ok := t.droppedSeries[e.Ref]; !ok {
 				level.Info(t.logger).Log("msg", "Dropped exemplar for series that was not explicitly dropped via relabelling", "ref", e.Ref)
+				t.metrics.droppedExemplarsTotal.WithLabelValues(reasonUnintentionalDroppedSeries).Inc()
+			} else {
+				t.metrics.droppedExemplarsTotal.WithLabelValues(reasonDroppedSeries).Inc()
 			}
 			t.seriesMtx.Unlock()
 			continue
@@ -678,16 +737,22 @@ func (t *QueueManager) AppendHistograms(histograms []record.RefHistogramSample)
 	if !t.sendNativeHistograms {
 		return true
 	}
-
+	currentTime := time.Now()
 outer:
 	for _, h := range histograms {
+		if isSampleOld(currentTime, time.Duration(t.cfg.SampleAgeLimit), h.T) {
+			t.metrics.droppedHistogramsTotal.WithLabelValues(reasonTooOld).Inc()
+			continue
+		}
 		t.seriesMtx.Lock()
 		lbls, ok := t.seriesLabels[h.Ref]
 		if !ok {
-			t.metrics.droppedHistogramsTotal.Inc()
 			t.dataDropped.incr(1)
 			if _, ok := t.droppedSeries[h.Ref]; !ok {
 				level.Info(t.logger).Log("msg", "Dropped histogram for series that was not explicitly dropped via relabelling", "ref", h.Ref)
+				t.metrics.droppedHistogramsTotal.WithLabelValues(reasonUnintentionalDroppedSeries).Inc()
+			} else {
+				t.metrics.droppedHistogramsTotal.WithLabelValues(reasonDroppedSeries).Inc()
 			}
 			t.seriesMtx.Unlock()
 			continue
@@ -725,16 +790,22 @@ func (t *QueueManager) AppendFloatHistograms(floatHistograms []record.RefFloatHi
 	if !t.sendNativeHistograms {
 		return true
 	}
-
+	currentTime := time.Now()
 outer:
 	for _, h := range floatHistograms {
+		if isSampleOld(currentTime, time.Duration(t.cfg.SampleAgeLimit), h.T) {
+			t.metrics.droppedHistogramsTotal.WithLabelValues(reasonTooOld).Inc()
+			continue
+		}
 		t.seriesMtx.Lock()
 		lbls, ok := t.seriesLabels[h.Ref]
 		if !ok {
-			t.metrics.droppedHistogramsTotal.Inc()
 			t.dataDropped.incr(1)
 			if _, ok := t.droppedSeries[h.Ref]; !ok {
 				level.Info(t.logger).Log("msg", "Dropped histogram for series that was not explicitly dropped via relabelling", "ref", h.Ref)
+				t.metrics.droppedHistogramsTotal.WithLabelValues(reasonUnintentionalDroppedSeries).Inc()
+			} else {
+				t.metrics.droppedHistogramsTotal.WithLabelValues(reasonDroppedSeries).Inc()
 			}
 			t.seriesMtx.Unlock()
 			continue
@@ -1490,7 +1561,8 @@ func (s *shards) sendSamples(ctx context.Context, samples []prompb.TimeSeries, s
 // sendSamples to the remote storage with backoff for recoverable errors.
 func (s *shards) sendSamplesWithBackoff(ctx context.Context, samples []prompb.TimeSeries, sampleCount, exemplarCount, histogramCount int, pBuf *proto.Buffer, buf *[]byte) error {
 	// Build the WriteRequest with no metadata.
-	req, highest, err := buildWriteRequest(samples, nil, pBuf, *buf)
+	req, highest, lowest, err := buildWriteRequest(s.qm.logger, samples, nil, pBuf, *buf, nil)
+	s.qm.buildRequestLimitTimestamp.Store(lowest)
 	if err != nil {
 		// Failing to build the write request is non-recoverable, since it will
 		// only error if marshaling the proto to bytes fails.
@@ -1504,6 +1576,25 @@ func (s *shards) sendSamplesWithBackoff(ctx context.Context, samples []prompb.Ti
 	// without causing a memory leak, and it has the nice effect of not propagating any
 	// parameters for sendSamplesWithBackoff/3.
 	attemptStore := func(try int) error {
+		currentTime := time.Now()
+		lowest := s.qm.buildRequestLimitTimestamp.Load()
+		if isSampleOld(currentTime, time.Duration(s.qm.cfg.SampleAgeLimit), lowest) {
+			// This will filter out old samples during retries.
+			req, _, lowest, err := buildWriteRequest(
+				s.qm.logger,
+				samples,
+				nil,
+				pBuf,
+				*buf,
+				isTimeSeriesOldFilter(s.qm.metrics, currentTime, time.Duration(s.qm.cfg.SampleAgeLimit)),
+			)
+			s.qm.buildRequestLimitTimestamp.Store(lowest)
+			if err != nil {
+				return err
+			}
+			*buf = req
+		}
+
 		ctx, span := otel.Tracer("").Start(ctx, "Remote Send Batch")
 		defer span.End()
 
@@ -1608,9 +1699,27 @@ func sendWriteRequestWithBackoff(ctx context.Context, cfg config.QueueConfig, l
 	}
 }
 
-func buildWriteRequest(samples []prompb.TimeSeries, metadata []prompb.MetricMetadata, pBuf *proto.Buffer, buf []byte) ([]byte, int64, error) {
+func buildTimeSeries(timeSeries []prompb.TimeSeries, filter func(prompb.TimeSeries) bool) (int64, int64, []prompb.TimeSeries, int, int, int) {
 	var highest int64
-	for _, ts := range samples {
+	var lowest int64
+	var droppedSamples, droppedExemplars, droppedHistograms int
+
+	keepIdx := 0
+	lowest = math.MaxInt64
+	for i, ts := range timeSeries {
+		if filter != nil && filter(ts) {
+			if len(ts.Samples) > 0 {
+				droppedSamples++
+			}
+			if len(ts.Exemplars) > 0 {
+				droppedExemplars++
+			}
+			if len(ts.Histograms) > 0 {
+				droppedHistograms++
+			}
+			continue
+		}
+
 		// At the moment we only ever append a TimeSeries with a single sample or exemplar in it.
 		if len(ts.Samples) > 0 && ts.Samples[0].Timestamp > highest {
 			highest = ts.Samples[0].Timestamp
@@ -1621,10 +1730,37 @@ func buildWriteRequest(samples []prompb.TimeSeries, metadata []prompb.MetricMeta
 		if len(ts.Histograms) > 0 && ts.Histograms[0].Timestamp > highest {
 			highest = ts.Histograms[0].Timestamp
 		}
+
+		// Get lowest timestamp
+		if len(ts.Samples) > 0 && ts.Samples[0].Timestamp < lowest {
+			lowest = ts.Samples[0].Timestamp
+		}
+		if len(ts.Exemplars) > 0 && ts.Exemplars[0].Timestamp < lowest {
+			lowest = ts.Exemplars[0].Timestamp
+		}
+		if len(ts.Histograms) > 0 && ts.Histograms[0].Timestamp < lowest {
+			lowest = ts.Histograms[0].Timestamp
+		}
+
+		// Move the current element to the write position and increment the write pointer
+		timeSeries[keepIdx] = timeSeries[i]
+		keepIdx++
+	}
+
+	timeSeries = timeSeries[:keepIdx]
+	return highest, lowest, timeSeries, droppedSamples, droppedExemplars, droppedHistograms
+}
+
+func buildWriteRequest(logger log.Logger, timeSeries []prompb.TimeSeries, metadata []prompb.MetricMetadata, pBuf *proto.Buffer, buf []byte, filter func(prompb.TimeSeries) bool) ([]byte, int64, int64, error) {
+	highest, lowest, timeSeries,
+		droppedSamples, droppedExemplars, droppedHistograms := buildTimeSeries(timeSeries, filter)
+
+	if droppedSamples > 0 || droppedExemplars > 0 || droppedHistograms > 0 {
+		level.Debug(logger).Log("msg", "dropped data due to their age", "droppedSamples", droppedSamples, "droppedExemplars", droppedExemplars, "droppedHistograms", droppedHistograms)
 	}
 
 	req := &prompb.WriteRequest{
-		Timeseries: samples,
+		Timeseries: timeSeries,
 		Metadata:   metadata,
 	}
 
@@ -1635,7 +1771,7 @@ func buildWriteRequest(samples []prompb.TimeSeries, metadata []prompb.MetricMeta
 	}
 	err := pBuf.Marshal(req)
 	if err != nil {
-		return nil, highest, err
+		return nil, highest, lowest, err
 	}
 
 	// snappy uses len() to see if it needs to allocate a new slice. Make the
@@ -1644,5 +1780,5 @@ func buildWriteRequest(samples []prompb.TimeSeries, metadata []prompb.MetricMeta
 		buf = buf[0:cap(buf)]
 	}
 	compressed := snappy.Encode(buf, pBuf.Bytes())
-	return compressed, highest, nil
+	return compressed, highest, lowest, nil
 }