Merge pull request #1326 from DeleurApps/fallbackSeries

Added fallbackSeries function

docs/graphite.md

@@ -74,7 +74,7 @@ See also:
 | events                                                         |              | No         |
 | exclude(seriesList, pattern) seriesList                        |              | Stable     |
 | exponentialMovingAverage                                       |              | No         |
-| fallbackSeries                                                 |              | No         |
+| fallbackSeries                                                 |              | Stable     |
 | filterSeries(seriesList, func, operator, threshold) seriesList |              | Stable     |
 | grep(seriesList, pattern) seriesList                           |              | Stable     |
 | group                                                          |              | No         |

expr/func_fallbackSeries.go

@@ -0,0 +1,40 @@
+package expr
+
+import (
+	"github.com/grafana/metrictank/api/models"
+)
+
+type FuncFallbackSeries struct {
+	in       GraphiteFunc
+	fallback GraphiteFunc
+}
+
+func NewFallbackSeries() GraphiteFunc {
+	return &FuncFallbackSeries{}
+}
+
+func (s *FuncFallbackSeries) Signature() ([]Arg, []Arg) {
+	return []Arg{
+		ArgSeriesList{val: &s.in},
+		ArgSeriesList{val: &s.fallback, key: "fallback"},
+	}, []Arg{ArgSeriesList{}}
+}
+
+func (s *FuncFallbackSeries) Context(context Context) Context {
+	return context
+}
+
+func (s *FuncFallbackSeries) Exec(cache map[Req][]models.Series) ([]models.Series, error) {
+	series, err := s.in.Exec(cache)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(series) == 0 {
+		series, err = s.fallback.Exec(cache)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return series, nil
+}

expr/func_fallbackseries_test.go

@@ -0,0 +1,76 @@
+package expr
+
+import (
+	"testing"
+
+	"github.com/grafana/metrictank/api/models"
+)
+
+func getNewFallbackSeries(in []models.Series, fallback []models.Series) *FuncFallbackSeries {
+	f := NewFallbackSeries()
+	s := f.(*FuncFallbackSeries)
+	s.in = NewMock(in)
+	s.fallback = NewMock(fallback)
+	return s
+}
+
+func TestFallbackSeriesNo(t *testing.T) {
+	f := getNewFallbackSeries(
+		[]models.Series{
+			{
+				Interval:   10,
+				QueryPatt:  "a",
+				Target:     "a",
+				Datapoints: getCopy(a),
+			},
+		},
+		[]models.Series{
+			{
+				Interval:   10,
+				QueryPatt:  "b",
+				Target:     "b",
+				Datapoints: getCopy(b),
+			},
+		},
+	)
+	out := []models.Series{
+		{
+			Interval:   10,
+			QueryPatt:  "a",
+			Target:     "a",
+			Datapoints: getCopy(a),
+		},
+	}
+
+	got, err := f.Exec(make(map[Req][]models.Series))
+	if err := equalOutput(out, got, nil, err); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestFallbackSeriesYes(t *testing.T) {
+	f := getNewFallbackSeries(
+		[]models.Series{},
+		[]models.Series{
+			{
+				Interval:   10,
+				QueryPatt:  "b",
+				Target:     "b",
+				Datapoints: getCopy(b),
+			},
+		},
+	)
+	out := []models.Series{
+		{
+			Interval:   10,
+			QueryPatt:  "b",
+			Target:     "b",
+			Datapoints: getCopy(b),
+		},
+	}
+
+	got, err := f.Exec(make(map[Req][]models.Series))
+	if err := equalOutput(out, got, nil, err); err != nil {
+		t.Fatal(err)
+	}
+}

expr/funcs.go

@@ -68,6 +68,7 @@ func init() {
 		"divideSeries":          {NewDivideSeries, true},
 		"divideSeriesLists":     {NewDivideSeriesLists, true},
 		"exclude":               {NewExclude, true},
+		"fallbackSeries":        {NewFallbackSeries, true},
 		"filterSeries":          {NewFilterSeries, true},
 		"grep":                  {NewGrep, true},
 		"groupByTags":           {NewGroupByTags, true},