Prometheus: Support 1ms resolution intervals (#44707)

* Prometheus: Support 1ms resolution in time ranges

* UI: Support 1ms resolution in time ranges

pkg/tsdb/cloudmonitoring/time_series_query_test.go

@@ -104,7 +104,7 @@ func TestTimeSeriesQuery(t *testing.T) {
 
 	t.Run("appends graph_period to the query", func(t *testing.T) {
 		query := &cloudMonitoringTimeSeriesQuery{}
-		assert.Equal(t, query.appendGraphPeriod(&backend.QueryDataRequest{Queries: []backend.DataQuery{{}}}), " | graph_period 10ms")
+		assert.Equal(t, query.appendGraphPeriod(&backend.QueryDataRequest{Queries: []backend.DataQuery{{}}}), " | graph_period 1ms")
 	})
 
 	t.Run("skips graph_period if disabled", func(t *testing.T) {

pkg/tsdb/intervalv2/intervalv2.go

@@ -159,6 +159,9 @@ func FormatDuration(inter time.Duration) string {
 //nolint: gocyclo
 func roundInterval(interval time.Duration) time.Duration {
 	switch {
+	// 0.01s
+	case interval <= 10*time.Millisecond:
+		return time.Millisecond * 1 // 0.001s
 	// 0.015s
 	case interval <= 15*time.Millisecond:
 		return time.Millisecond * 10 // 0.01s

pkg/tsdb/intervalv2/intervalv2_test.go

@@ -70,6 +70,8 @@ func TestRoundInterval(t *testing.T) {
 		interval time.Duration
 		expected time.Duration
 	}{
+		{"10ms", time.Millisecond * 10, time.Millisecond * 1},
+		{"15ms", time.Millisecond * 15, time.Millisecond * 10},
 		{"30ms", time.Millisecond * 30, time.Millisecond * 20},
 		{"45ms", time.Millisecond * 45, time.Millisecond * 50},
 	}

pkg/tsdb/prometheus/buffered/time_series_query.go

@@ -630,7 +630,9 @@ func newDataFrame(name string, typ string, fields ...*data.Field) *data.Frame {
 }
 
 func alignTimeRange(t time.Time, step time.Duration, offset int64) time.Time {
-	return time.Unix(int64(math.Floor((float64(t.Unix()+offset)/step.Seconds()))*step.Seconds()-float64(offset)), 0)
+	offsetNano := float64(offset * 1e9)
+	stepNano := float64(step.Nanoseconds())
+	return time.Unix(0, int64(math.Floor((float64(t.UnixNano())+offsetNano)/stepNano)*stepNano-offsetNano))
 }
 
 func isVariableInterval(interval string) bool {