[chore][fileconsumer] Fix flush test (#37598)

Author: djaglowski

pkg/stanza/fileconsumer/internal/reader/reader_test.go

@@ -196,17 +196,30 @@ func TestFlushPeriodEOF(t *testing.T) {
 	_, err := temp.WriteString(string(content))
 	require.NoError(t, err)
 
-	// Make sure FlushPeriod is small, so it is guaranteed to expire
-	f, sink := testFactory(t, withFlushPeriod(5*time.Nanosecond))
+	flushPeriod := time.Millisecond
+	f, sink := testFactory(t, withFlushPeriod(flushPeriod))
 	fp, err := f.NewFingerprint(temp)
 	require.NoError(t, err)
 	r, err := f.NewReader(temp, fp)
 	require.NoError(t, err)
 	assert.Equal(t, int64(0), r.Offset)
 
-	internaltime.Now = internaltime.NewAlwaysIncreasingClock().Now
-	defer func() { internaltime.Now = time.Now }()
+	clock := internaltime.NewAlwaysIncreasingClock()
+	internaltime.Now = clock.Now
+	internaltime.Since = clock.Since
+	defer func() {
+		internaltime.Now = time.Now
+		internaltime.Since = time.Since
+	}()
 
+	// First ReadToEnd should not emit only the terminated token
 	r.ReadToEnd(context.Background())
-	sink.ExpectTokens(t, content[0:aContentLength], []byte{'b'})
+	sink.ExpectToken(t, content[0:aContentLength])
+
+	// Advance time past the flush period
+	clock.Advance(2 * flushPeriod)
+
+	// Second ReadToEnd should emit the unterminated token because of flush timeout
+	r.ReadToEnd(context.Background())
+	sink.ExpectToken(t, []byte{'b'})
 }

pkg/stanza/flush/flush.go

@@ -15,16 +15,6 @@ type State struct {
 	LastDataLength int
 }
 
-func (s *State) Copy() *State {
-	if s == nil {
-		return nil
-	}
-	return &State{
-		LastDataChange: s.LastDataChange,
-		LastDataLength: s.LastDataLength,
-	}
-}
-
 // Func wraps a bufio.SplitFunc with a timer.
 // When the timer expires, an incomplete token may be returned.
 // The timer will reset any time the data parameter changes.
@@ -61,7 +51,7 @@ func (s *State) Func(splitFunc bufio.SplitFunc, period time.Duration) bufio.Spli
 		}
 
 		// Flush timed out
-		if time.Since(s.LastDataChange) > period {
+		if internaltime.Since(s.LastDataChange) > period {
 			s.LastDataChange = internaltime.Now()
 			s.LastDataLength = 0
 			return len(data), data, nil