Optimize ts v2 pool

Signed-off-by: SungJin1212 <tjdwls1201@gmail.com>

Author: SungJin1212

pkg/cortexpb/timeseriesv2.go

@@ -77,6 +77,10 @@ func ReuseWriteRequestV2(req *PreallocWriteRequestV2) {
 		req.data = nil
 	}
 	req.Source = 0
+
+	for i := range req.Symbols {
+		req.Symbols[i] = ""
+	}
 	req.Symbols = req.Symbols[:0]
 	if req.Timeseries != nil {
 		ReuseSliceV2(req.Timeseries)
@@ -121,11 +125,6 @@ func ReuseTimeseriesV2(ts *TimeSeriesV2) {
 	ts.Metadata.UnitRef = 0
 	ts.Metadata.HelpRef = 0
 
-	// clear exemplar label refs
-	for i := range ts.Exemplars {
-		ts.Exemplars[i].LabelsRefs = ts.Exemplars[i].LabelsRefs[:0]
-	}
-
 	for i := range ts.Histograms {
 		ts.Histograms[i].Reset()
 	}

pkg/cortexpb/timeseriesv2_test.go

@@ -52,6 +52,38 @@ func TestTimeseriesV2FromPool(t *testing.T) {
 	})
 }
 
+func TestReuseWriteRequestV2(t *testing.T) {
+	req := PreallocWriteRequestV2FromPool()
+
+	// Populate req with some data.
+	req.Source = RULE
+	req.Symbols = append(req.Symbols, "", "__name__", "test")
+
+	tsSlice := PreallocTimeseriesV2SliceFromPool()
+	tsSlice = append(tsSlice, PreallocTimeseriesV2{TimeSeriesV2: TimeseriesV2FromPool()})
+	req.Timeseries = tsSlice
+
+	// Put the request back into the pool
+	ReuseWriteRequestV2(req)
+
+	// Retrieve it from the pool again
+	reused := PreallocWriteRequestV2FromPool()
+
+	// Source is reset to default
+	assert.Equal(t, API, reused.Source)
+	// The symbol length is properly reset to 0.
+	assert.Len(t, reused.Symbols, 0)
+	// Timeseries slice is nil
+	assert.Nil(t, reused.Timeseries)
+
+	// The underlying array's string pointers are cleared to "" to prevent memory leak.
+	if cap(reused.Symbols) > 0 {
+		underlyingArray := reused.Symbols[:cap(reused.Symbols)]
+		assert.Equal(t, "", underlyingArray[0])
+		assert.Equal(t, "", underlyingArray[1])
+	}
+}
+
 func BenchmarkMarshallWriteRequestV2(b *testing.B) {
 	ts := PreallocTimeseriesV2SliceFromPool()