fix(wlog/watcher_test.go): make TestRun_AvoidNotifyWhenBehind more resilient

Signed-off-by: machine424 <ayoubmrini424@gmail.com>

tsdb/wlog/watcher_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/go-kit/log"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sync/errgroup"
 
 	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
@@ -52,6 +53,13 @@ func retry(t *testing.T, interval time.Duration, n int, f func() bool) {
 	t.Logf("function returned false")
 }
 
+// Overwrite readTimeout defined in watcher.go.
+func overwriteReadTimeout(t *testing.T, val time.Duration) {
+	initialVal := readTimeout
+	readTimeout = val
+	t.Cleanup(func() { readTimeout = initialVal })
+}
+
 type writeToMock struct {
 	samplesAppended         int
 	exemplarsAppended       int
@@ -302,7 +310,7 @@ func TestReadToEndNoCheckpoint(t *testing.T) {
 				}
 			}
 			require.NoError(t, w.Log(recs...))
-			readTimeout = time.Second
+			overwriteReadTimeout(t, time.Second)
 			_, _, err = Segments(w.Dir())
 			require.NoError(t, err)
 
@@ -394,7 +402,7 @@ func TestReadToEndWithCheckpoint(t *testing.T) {
 
 			_, _, err = Segments(w.Dir())
 			require.NoError(t, err)
-			readTimeout = time.Second
+			overwriteReadTimeout(t, time.Second)
 			wt := newWriteToMock(0)
 			watcher := NewWatcher(wMetrics, nil, nil, "", wt, dir, false, false, false)
 			go watcher.Start()
@@ -607,7 +615,7 @@ func TestCheckpointSeriesReset(t *testing.T) {
 			_, _, err = Segments(w.Dir())
 			require.NoError(t, err)
 
-			readTimeout = time.Second
+			overwriteReadTimeout(t, time.Second)
 			wt := newWriteToMock(0)
 			watcher := NewWatcher(wMetrics, nil, nil, "", wt, dir, false, false, false)
 			watcher.MaxSegment = -1
@@ -742,9 +750,6 @@ func TestRun_AvoidNotifyWhenBehind(t *testing.T) {
 	const seriesCount = 10
 	const samplesCount = 50
 
-	// This test can take longer than intended to finish in cloud CI.
-	readTimeout := 10 * time.Second
-
 	for _, compress := range []CompressionType{CompressionNone, CompressionSnappy, CompressionZstd} {
 		t.Run(string(compress), func(t *testing.T) {
 			dir := t.TempDir()
@@ -755,36 +760,50 @@ func TestRun_AvoidNotifyWhenBehind(t *testing.T) {
 
 			w, err := NewSize(nil, nil, wdir, segmentSize, compress)
 			require.NoError(t, err)
-			var wg sync.WaitGroup
-			// Generate one segment initially to ensure that watcher.Run() finds at least one segment on disk.
+			// Write to 00000000, the watcher will read series from it.
 			require.NoError(t, generateWALRecords(w, 0, seriesCount, samplesCount))
-			w.NextSegment() // Force creation of the next segment
-			wg.Add(1)
-			go func() {
-				defer wg.Done()
+			// Create 00000001, the watcher will tail it once started.
+			w.NextSegment()
+
+			// Set up the watcher and run it in the background.
+			wt := newWriteToMock(time.Millisecond)
+			watcher := NewWatcher(wMetrics, nil, nil, "", wt, dir, false, false, false)
+			watcher.setMetrics()
+			watcher.MaxSegment = segmentsToRead
+
+			var g errgroup.Group
+			g.Go(func() error {
+				startTime := time.Now()
+				err = watcher.Run()
+				if err != nil {
+					return err
+				}
+				// If the watcher was to wait for readTicker to read every new segment, it would need readTimeout * segmentsToRead.
+				d := time.Since(startTime)
+				if d > readTimeout {
+					return fmt.Errorf("watcher ran for %s, it shouldn't rely on readTicker=%s to read the new segments", d, readTimeout)
+				}
+				return nil
+			})
+
+			// The watcher went through 00000000 and is tailing the next one.
+			retry(t, defaultRetryInterval, defaultRetries, func() bool {
+				return wt.checkNumSeries() == seriesCount
+			})
+
+			// In the meantime, add some new segments in bulk.
+			// We should end up with segmentsToWrite + 1 segments now.
 			for i := 1; i < segmentsToWrite; i++ {
 				require.NoError(t, generateWALRecords(w, i, seriesCount, samplesCount))
 				w.NextSegment()
 			}
-			}()
 
-			wt := newWriteToMock(time.Millisecond)
-			watcher := NewWatcher(wMetrics, nil, nil, "", wt, dir, false, false, false)
-			watcher.MaxSegment = segmentsToRead
+			// Wait for the watcher.
+			require.NoError(t, g.Wait())
 
-			watcher.setMetrics()
-			startTime := time.Now()
-			err = watcher.Run()
-			wg.Wait()
-			require.Less(t, time.Since(startTime), readTimeout)
-
-			// But samples records shouldn't get dropped
-			retry(t, defaultRetryInterval, defaultRetries, func() bool {
-				return wt.checkNumSeries() > 0
-			})
+			// All series and samples were read.
+			require.Equal(t, (segmentsToRead+1)*seriesCount, wt.checkNumSeries()) // Series from 00000000 are also read.
 			require.Equal(t, segmentsToRead*seriesCount*samplesCount, wt.samplesAppended)
-
-			require.NoError(t, err)
 			require.NoError(t, w.Close())
 		})
 	}