Update head time when reading wal

head.go

@@ -199,12 +199,15 @@ func NewHead(r prometheus.Registerer, l log.Logger, wal WAL, chunkRange int64) (
 // processWALSamples adds a partition of samples it receives to the head and passes
 // them on to other workers.
 // Samples before the mint timestamp are discarded.
+// Returns the mint and maxt of all processed samples.
 func (h *Head) processWALSamples(
 	mint int64,
 	partition, total uint64,
 	input <-chan []RefSample, output chan<- []RefSample,
-) (unknownRefs uint64) {
+) (unknownRefs uint64, smint, smaxt int64) {
 	defer close(output)
+	smint = math.MaxInt64 // Start with Maxint64 and go down from here.
+	smaxt = math.MinInt64 // Start with MinInt64 and go up from here.
 
 	for samples := range input {
 		for _, s := range samples {
@@ -221,10 +224,18 @@ func (h *Head) processWALSamples(
 				h.metrics.chunksCreated.Inc()
 				h.metrics.chunks.Inc()
 			}
+
+			if s.T < smint {
+				smint = s.T
+			}
+
+			if s.T > smaxt {
+				smaxt = s.T
+			}
 		}
 		output <- samples
 	}
-	return unknownRefs
+	return unknownRefs, smint, smaxt
 }
 
 // ReadWAL initializes the head by consuming the write ahead log.
@@ -253,8 +264,20 @@ func (h *Head) ReadWAL() error {
 		output := make(chan []RefSample, 300)
 
 		go func(i int, input <-chan []RefSample, output chan<- []RefSample) {
-			unknown := h.processWALSamples(mint, uint64(i), uint64(n), input, output)
+			unknown, smint, smaxt := h.processWALSamples(mint, uint64(i), uint64(n), input, output)
 			atomic.AddUint64(&unknownRefs, unknown)
+
+			if h.minTime == math.MinInt64 {
+				h.minTime = smint
+			}
+
+			if h.minTime > smint {
+				h.minTime = smint
+			}
+
+			if h.maxTime < smaxt {
+				h.maxTime = smaxt
+			}
 			wg.Done()
 		}(i, input, output)
 

head_test.go

@@ -74,14 +74,14 @@ func TestHead_ReadWAL(t *testing.T) {
 		},
 		[]RefSample{
 			{Ref: 0, T: 99, V: 1},
-			{Ref: 10, T: 100, V: 2},
+			{Ref: 10, T: 1, V: 2},
 			{Ref: 100, T: 100, V: 3},
 		},
 		[]RefSeries{
 			{Ref: 50, Labels: labels.FromStrings("a", "4")},
 		},
 		[]RefSample{
-			{Ref: 10, T: 101, V: 5},
+			{Ref: 10, T: 2, V: 5},
 			{Ref: 50, T: 101, V: 6},
 		},
 	}
@@ -93,6 +93,8 @@ func TestHead_ReadWAL(t *testing.T) {
 
 	testutil.Ok(t, head.ReadWAL())
 	testutil.Equals(t, uint64(100), head.lastSeriesID)
+	testutil.Equals(t, int64(1), head.MinTime())
+	testutil.Equals(t, int64(101), head.MaxTime())
 
 	s10 := head.series.getByID(10)
 	s11 := head.series.getByID(11)
@@ -113,7 +115,7 @@ func TestHead_ReadWAL(t *testing.T) {
 		return x
 	}
 
-	testutil.Equals(t, []sample{{100, 2}, {101, 5}}, expandChunk(s10.iterator(0)))
+	testutil.Equals(t, []sample{{1, 2}, {2, 5}}, expandChunk(s10.iterator(0)))
 	testutil.Equals(t, 0, len(s11.chunks))
 	testutil.Equals(t, []sample{{101, 6}}, expandChunk(s50.iterator(0)))
 	testutil.Equals(t, []sample{{100, 3}}, expandChunk(s100.iterator(0)))