agent db: make rejecting ooo samples configurable (#14094)

feat: Make OOO ingestion time window configurable for Prometheus Agent.

Signed-off-by: Sebastian Rabenhorst <sebastian.rabenhorst@shopify.com>

cmd/prometheus/main.go

@@ -1197,7 +1197,7 @@ func main() {
 	}
 	if agentMode {
 		// WAL storage.
-		opts := cfg.agent.ToAgentOptions()
+		opts := cfg.agent.ToAgentOptions(cfg.tsdb.OutOfOrderTimeWindow)
 		cancel := make(chan struct{})
 		g.Add(
 			func() error {
@@ -1233,6 +1233,7 @@ func main() {
 					"TruncateFrequency", cfg.agent.TruncateFrequency,
 					"MinWALTime", cfg.agent.MinWALTime,
 					"MaxWALTime", cfg.agent.MaxWALTime,
+					"OutOfOrderTimeWindow", cfg.agent.OutOfOrderTimeWindow,
 				)
 
 				localStorage.Set(db, 0)
@@ -1736,9 +1737,13 @@ type agentOptions struct {
 	TruncateFrequency      model.Duration
 	MinWALTime, MaxWALTime model.Duration
 	NoLockfile             bool
+	OutOfOrderTimeWindow   int64
 }
 
-func (opts agentOptions) ToAgentOptions() agent.Options {
+func (opts agentOptions) ToAgentOptions(outOfOrderTimeWindow int64) agent.Options {
+	if outOfOrderTimeWindow < 0 {
+		outOfOrderTimeWindow = 0
+	}
 	return agent.Options{
 		WALSegmentSize:       int(opts.WALSegmentSize),
 		WALCompression:       wlog.ParseCompressionType(opts.WALCompression, opts.WALCompressionType),
@@ -1747,6 +1752,7 @@ func (opts agentOptions) ToAgentOptions() agent.Options {
 		MinWALTime:           durationToInt64Millis(time.Duration(opts.MinWALTime)),
 		MaxWALTime:           durationToInt64Millis(time.Duration(opts.MaxWALTime)),
 		NoLockfile:           opts.NoLockfile,
+		OutOfOrderTimeWindow: outOfOrderTimeWindow,
 	}
 }
 

docs/configuration/configuration.md

@@ -3813,6 +3813,10 @@ NOTE: Out-of-order ingestion is an experimental feature, but you do not need any
 # into the TSDB, i.e. it is an in-order sample or an out-of-order/out-of-bounds sample
 # that is within the out-of-order window, or (b) too-old, i.e. not in-order
 # and before the out-of-order window.
+#
+# When out_of_order_time_window is greater than 0, it also affects experimental agent. It allows 
+# the agent's WAL to accept out-of-order samples that fall within the specified time window relative 
+# to the timestamp of the last appended sample for the same series.
 [ out_of_order_time_window: <duration> | default = 0s ]
 ```
 

tsdb/agent/db.go

@@ -81,6 +81,9 @@ type Options struct {
 
 	// NoLockfile disables creation and consideration of a lock file.
 	NoLockfile bool
+
+	// OutOfOrderTimeWindow specifies how much out of order is allowed, if any.
+	OutOfOrderTimeWindow int64
 }
 
 // DefaultOptions used for the WAL storage. They are reasonable for setups using
@@ -94,6 +97,7 @@ func DefaultOptions() *Options {
 		MinWALTime:           DefaultMinWALTime,
 		MaxWALTime:           DefaultMaxWALTime,
 		NoLockfile:           false,
+		OutOfOrderTimeWindow: 0,
 	}
 }
 
@@ -812,6 +816,11 @@ func (a *appender) Append(ref storage.SeriesRef, l labels.Labels, t int64, v flo
 	series.Lock()
 	defer series.Unlock()
 
+	if t <= a.minValidTime(series.lastTs) {
+		a.metrics.totalOutOfOrderSamples.Inc()
+		return 0, storage.ErrOutOfOrderSample
+	}
+
 	// NOTE: always modify pendingSamples and sampleSeries together.
 	a.pendingSamples = append(a.pendingSamples, record.RefSample{
 		Ref: series.ref,
@@ -935,6 +944,11 @@ func (a *appender) AppendHistogram(ref storage.SeriesRef, l labels.Labels, t int
 	series.Lock()
 	defer series.Unlock()
 
+	if t <= a.minValidTime(series.lastTs) {
+		a.metrics.totalOutOfOrderSamples.Inc()
+		return 0, storage.ErrOutOfOrderSample
+	}
+
 	switch {
 	case h != nil:
 		// NOTE: always modify pendingHistograms and histogramSeries together
@@ -1103,3 +1117,13 @@ func (a *appender) logSeries() error {
 
 	return nil
 }
+
+// mintTs returns the minimum timestamp that a sample can have
+// and is needed for preventing underflow.
+func (a *appender) minValidTime(lastTs int64) int64 {
+	if lastTs < math.MinInt64+a.opts.OutOfOrderTimeWindow {
+		return math.MinInt64
+	}
+
+	return lastTs - a.opts.OutOfOrderTimeWindow
+}

tsdb/agent/db_test.go

@@ -16,6 +16,7 @@ package agent
 import (
 	"context"
 	"fmt"
+	"math"
 	"path/filepath"
 	"strconv"
 	"testing"
@@ -761,7 +762,9 @@ func TestDBAllowOOOSamples(t *testing.T) {
 	)
 
 	reg := prometheus.NewRegistry()
-	s := createTestAgentDB(t, reg, DefaultOptions())
+	opts := DefaultOptions()
+	opts.OutOfOrderTimeWindow = math.MaxInt64
+	s := createTestAgentDB(t, reg, opts)
 	app := s.Appender(context.TODO())
 
 	// Let's add some samples in the [offset, offset+numDatapoints) range.
@@ -879,6 +882,56 @@ func TestDBAllowOOOSamples(t *testing.T) {
 	require.NoError(t, db.Close())
 }
 
+func TestDBOutOfOrderTimeWindow(t *testing.T) {
+	tc := []struct {
+		outOfOrderTimeWindow, firstTs, secondTs int64
+		expectedError                           error
+	}{
+		{0, 100, 101, nil},
+		{0, 100, 100, storage.ErrOutOfOrderSample},
+		{0, 100, 99, storage.ErrOutOfOrderSample},
+		{100, 100, 1, nil},
+		{100, 100, 0, storage.ErrOutOfOrderSample},
+	}
+
+	for _, c := range tc {
+		t.Run(fmt.Sprintf("outOfOrderTimeWindow=%d, firstTs=%d, secondTs=%d, expectedError=%s", c.outOfOrderTimeWindow, c.firstTs, c.secondTs, c.expectedError), func(t *testing.T) {
+			reg := prometheus.NewRegistry()
+			opts := DefaultOptions()
+			opts.OutOfOrderTimeWindow = c.outOfOrderTimeWindow
+			s := createTestAgentDB(t, reg, opts)
+			app := s.Appender(context.TODO())
+
+			lbls := labelsForTest(t.Name()+"_histogram", 1)
+			lset := labels.New(lbls[0]...)
+			_, err := app.AppendHistogram(0, lset, c.firstTs, tsdbutil.GenerateTestHistograms(1)[0], nil)
+			require.NoError(t, err)
+			err = app.Commit()
+			require.NoError(t, err)
+			_, err = app.AppendHistogram(0, lset, c.secondTs, tsdbutil.GenerateTestHistograms(1)[0], nil)
+			require.ErrorIs(t, err, c.expectedError)
+
+			lbls = labelsForTest(t.Name(), 1)
+			lset = labels.New(lbls[0]...)
+			_, err = app.Append(0, lset, c.firstTs, 0)
+			require.NoError(t, err)
+			err = app.Commit()
+			require.NoError(t, err)
+			_, err = app.Append(0, lset, c.secondTs, 0)
+			require.ErrorIs(t, err, c.expectedError)
+
+			expectedAppendedSamples := float64(2)
+			if c.expectedError != nil {
+				expectedAppendedSamples = 1
+			}
+			m := gatherFamily(t, reg, "prometheus_agent_samples_appended_total")
+			require.Equal(t, expectedAppendedSamples, m.Metric[0].Counter.GetValue(), "agent wal mismatch of total appended samples")
+			require.Equal(t, expectedAppendedSamples, m.Metric[1].Counter.GetValue(), "agent wal mismatch of total appended histograms")
+			require.NoError(t, s.Close())
+		})
+	}
+}
+
 func BenchmarkCreateSeries(b *testing.B) {
 	s := createTestAgentDB(b, nil, DefaultOptions())
 	defer s.Close()