[query] Implemented the Graphite grep function (#2655)

src/query/graphite/native/builtin_functions.go

@@ -205,6 +205,26 @@ func limit(_ *common.Context, series singlePathSpec, n int) (ts.SeriesList, erro
 	return r, nil
 }
 
+// grep takes a metric or a wildcard seriesList, followed by a regular
+// expression in double quotes. Excludes metrics that don’t match the regular expression.
+func grep(_ *common.Context, seriesList singlePathSpec, regex string) (ts.SeriesList, error) {
+	re, err := regexp.Compile(regex)
+	if err != nil {
+		return ts.NewSeriesList(), err
+	}
+
+	filtered := seriesList.Values[:0]
+	for _, series := range seriesList.Values {
+		if re.MatchString(series.Name()) {
+			filtered = append(filtered, series)
+		}
+	}
+
+	r := ts.NewSeriesList()
+	r.Values = filtered
+	return r, nil
+}
+
 // timeShift draws the selected metrics shifted in time. If no sign is given, a minus sign ( - ) is
 // implied which will shift the metric back in time. If a plus sign ( + ) is given, the metric will
 // be shifted forward in time
@@ -2205,6 +2225,7 @@ func init() {
 	MustRegisterFunction(exclude)
 	MustRegisterFunction(exponentialMovingAverage)
 	MustRegisterFunction(fallbackSeries)
+	MustRegisterFunction(grep)
 	MustRegisterFunction(group)
 	MustRegisterFunction(groupByNode)
 	MustRegisterFunction(groupByNodes)

src/query/graphite/native/builtin_functions_test.go

@@ -134,6 +134,44 @@ func TestExcludeErr(t *testing.T) {
 	require.Nil(t, results.Values)
 }
 
+func TestGrep(t *testing.T) {
+	ctx := common.NewTestContext()
+	defer ctx.Close()
+
+	now := time.Now()
+	values := ts.NewConstantValues(ctx, 10.0, 5, 10)
+
+	series1 := ts.NewSeries(ctx, "collectd.test-db1.load.value", now, values)
+	series2 := ts.NewSeries(ctx, "collectd.test-db2.load.value", now, values)
+	series3 := ts.NewSeries(ctx, "collectd.test-db3.load.value", now, values)
+	series4 := ts.NewSeries(ctx, "collectd.test-db4.load.value", now, values)
+
+	testInputs := []*ts.Series{series1, series2, series3, series4}
+	expectedOutput := []common.TestSeries{
+		{
+			Name: "collectd.test-db1.load.value",
+			Data: []float64{10.0, 10.0, 10.0, 10.0, 10.0},
+		},
+		{
+			Name: "collectd.test-db2.load.value",
+			Data: []float64{10.0, 10.0, 10.0, 10.0, 10.0},
+		},
+	}
+
+	results, err := grep(nil, singlePathSpec{
+		Values: testInputs,
+	}, ".*db[12]")
+	require.Nil(t, err)
+	require.NotNil(t, results)
+	common.CompareOutputsAndExpected(t, 10, now, expectedOutput, results.Values)
+
+	// error case
+	_, err = grep(nil, singlePathSpec{
+		Values: testInputs,
+	}, "+++++")
+	require.NotNil(t, err)
+}
+
 func TestSortByName(t *testing.T) {
 	ctx := common.NewTestContext()
 	defer ctx.Close()
@@ -3312,6 +3350,7 @@ func TestFunctionsRegistered(t *testing.T) {
 		"exclude",
 		"exponentialMovingAverage",
 		"fallbackSeries",
+		"grep",
 		"group",
 		"groupByNode",
 		"groupByNodes",