Merge pull request #13997 from bboreham/api-marshalling

bugfix: API: encode empty Vector/Matrix as [] not null

web/api/v1/api_test.go

@@ -15,7 +15,6 @@ package v1
 
 import (
 	"context"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -35,6 +34,7 @@ import (
 	"github.com/prometheus/prometheus/util/testutil"
 
 	"github.com/go-kit/log"
+	jsoniter "github.com/json-iterator/go"
 	"github.com/prometheus/client_golang/prometheus"
 	config_util "github.com/prometheus/common/config"
 	"github.com/prometheus/common/model"
@@ -910,6 +910,7 @@ func TestStats(t *testing.T) {
 				require.IsType(t, &QueryData{}, i)
 				qd := i.(*QueryData)
 				require.NotNil(t, qd.Stats)
+				json := jsoniter.ConfigCompatibleWithStandardLibrary
 				j, err := json.Marshal(qd.Stats)
 				require.NoError(t, err)
 				require.JSONEq(t, `{"custom":"Custom Value"}`, string(j))
@@ -1171,6 +1172,25 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, es storage.E
 				},
 			},
 		},
+		// Test empty vector result
+		{
+			endpoint: api.query,
+			query: url.Values{
+				"query": []string{"bottomk(2, notExists)"},
+			},
+			responseAsJSON: `{"resultType":"vector","result":[]}`,
+		},
+		// Test empty matrix result
+		{
+			endpoint: api.queryRange,
+			query: url.Values{
+				"query": []string{"bottomk(2, notExists)"},
+				"start": []string{"0"},
+				"end":   []string{"2"},
+				"step":  []string{"1"},
+			},
+			responseAsJSON: `{"resultType":"matrix","result":[]}`,
+		},
 		// Missing query params in range queries.
 		{
 			endpoint: api.queryRange,
@@ -2891,10 +2911,13 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, es storage.E
 						if test.zeroFunc != nil {
 							test.zeroFunc(res.data)
 						}
-						assertAPIResponse(t, res.data, test.response)
+						if test.response != nil {
+							assertAPIResponse(t, res.data, test.response)
+						}
 					}
 
 					if test.responseAsJSON != "" {
+						json := jsoniter.ConfigCompatibleWithStandardLibrary
 						s, err := json.Marshal(res.data)
 						require.NoError(t, err)
 						require.JSONEq(t, test.responseAsJSON, string(s))
@@ -3292,18 +3315,7 @@ func TestRespondError(t *testing.T) {
 	require.Equal(t, want, have, "Return code %d expected in error response but got %d", want, have)
 	h := resp.Header.Get("Content-Type")
 	require.Equal(t, "application/json", h, "Expected Content-Type %q but got %q", "application/json", h)
-
-	var res Response
-	err = json.Unmarshal(body, &res)
-	require.NoError(t, err, "Error unmarshaling JSON body")
-
-	exp := &Response{
-		Status:    statusError,
-		Data:      "test",
-		ErrorType: errorTimeout,
-		Error:     "message",
-	}
-	require.Equal(t, exp, &res)
+	require.JSONEq(t, `{"status": "error", "data": "test", "errorType": "timeout", "error": "message"}`, string(body))
 }
 
 func TestParseTimeParam(t *testing.T) {

web/api/v1/json_codec.go

@@ -25,11 +25,13 @@ import (
 )
 
 func init() {
-	jsoniter.RegisterTypeEncoderFunc("promql.Series", marshalSeriesJSON, marshalSeriesJSONIsEmpty)
-	jsoniter.RegisterTypeEncoderFunc("promql.Sample", marshalSampleJSON, marshalSampleJSONIsEmpty)
-	jsoniter.RegisterTypeEncoderFunc("promql.FPoint", marshalFPointJSON, marshalPointJSONIsEmpty)
-	jsoniter.RegisterTypeEncoderFunc("promql.HPoint", marshalHPointJSON, marshalPointJSONIsEmpty)
-	jsoniter.RegisterTypeEncoderFunc("exemplar.Exemplar", marshalExemplarJSON, marshalExemplarJSONEmpty)
+	jsoniter.RegisterTypeEncoderFunc("promql.Vector", unsafeMarshalVectorJSON, neverEmpty)
+	jsoniter.RegisterTypeEncoderFunc("promql.Matrix", unsafeMarshalMatrixJSON, neverEmpty)
+	jsoniter.RegisterTypeEncoderFunc("promql.Series", unsafeMarshalSeriesJSON, neverEmpty)
+	jsoniter.RegisterTypeEncoderFunc("promql.Sample", unsafeMarshalSampleJSON, neverEmpty)
+	jsoniter.RegisterTypeEncoderFunc("promql.FPoint", unsafeMarshalFPointJSON, neverEmpty)
+	jsoniter.RegisterTypeEncoderFunc("promql.HPoint", unsafeMarshalHPointJSON, neverEmpty)
+	jsoniter.RegisterTypeEncoderFunc("exemplar.Exemplar", marshalExemplarJSON, neverEmpty)
 	jsoniter.RegisterTypeEncoderFunc("labels.Labels", unsafeMarshalLabelsJSON, labelsIsEmpty)
 }
 
@@ -66,8 +68,12 @@ func (j JSONCodec) Encode(resp *Response) ([]byte, error) {
 //	      < more histograms >
 //	   ],
 //	},
-func marshalSeriesJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+func unsafeMarshalSeriesJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	s := *((*promql.Series)(ptr))
+	marshalSeriesJSON(s, stream)
+}
+
+func marshalSeriesJSON(s promql.Series, stream *jsoniter.Stream) {
 	stream.WriteObjectStart()
 	stream.WriteObjectField(`metric`)
 	marshalLabelsJSON(s.Metric, stream)
@@ -78,7 +84,7 @@ func marshalSeriesJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 			stream.WriteObjectField(`values`)
 			stream.WriteArrayStart()
 		}
-		marshalFPointJSON(unsafe.Pointer(&p), stream)
+		marshalFPointJSON(p, stream)
 	}
 	if len(s.Floats) > 0 {
 		stream.WriteArrayEnd()
@@ -89,15 +95,16 @@ func marshalSeriesJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 			stream.WriteObjectField(`histograms`)
 			stream.WriteArrayStart()
 		}
-		marshalHPointJSON(unsafe.Pointer(&p), stream)
+		marshalHPointJSON(p, stream)
 	}
 	if len(s.Histograms) > 0 {
 		stream.WriteArrayEnd()
 	}
 	stream.WriteObjectEnd()
 }
 
-func marshalSeriesJSONIsEmpty(unsafe.Pointer) bool {
+// In the Prometheus API we render an empty object as `[]` or similar.
+func neverEmpty(unsafe.Pointer) bool {
 	return false
 }
 
@@ -122,8 +129,12 @@ func marshalSeriesJSONIsEmpty(unsafe.Pointer) bool {
 //	   },
 //	   "histogram": [ 1435781451.781, { < histogram, see jsonutil.MarshalHistogram > } ]
 //	},
-func marshalSampleJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+func unsafeMarshalSampleJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	s := *((*promql.Sample)(ptr))
+	marshalSampleJSON(s, stream)
+}
+
+func marshalSampleJSON(s promql.Sample, stream *jsoniter.Stream) {
 	stream.WriteObjectStart()
 	stream.WriteObjectField(`metric`)
 	marshalLabelsJSON(s.Metric, stream)
@@ -145,13 +156,13 @@ func marshalSampleJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	stream.WriteObjectEnd()
 }
 
-func marshalSampleJSONIsEmpty(unsafe.Pointer) bool {
-	return false
-}
-
 // marshalFPointJSON writes `[ts, "1.234"]`.
-func marshalFPointJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+func unsafeMarshalFPointJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	p := *((*promql.FPoint)(ptr))
+	marshalFPointJSON(p, stream)
+}
+
+func marshalFPointJSON(p promql.FPoint, stream *jsoniter.Stream) {
 	stream.WriteArrayStart()
 	jsonutil.MarshalTimestamp(p.T, stream)
 	stream.WriteMore()
@@ -160,19 +171,19 @@ func marshalFPointJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 }
 
 // marshalHPointJSON writes `[ts, { < histogram, see jsonutil.MarshalHistogram > } ]`.
-func marshalHPointJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+func unsafeMarshalHPointJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	p := *((*promql.HPoint)(ptr))
+	marshalHPointJSON(p, stream)
+}
+
+func marshalHPointJSON(p promql.HPoint, stream *jsoniter.Stream) {
 	stream.WriteArrayStart()
 	jsonutil.MarshalTimestamp(p.T, stream)
 	stream.WriteMore()
 	jsonutil.MarshalHistogram(p.H, stream)
 	stream.WriteArrayEnd()
 }
 
-func marshalPointJSONIsEmpty(unsafe.Pointer) bool {
-	return false
-}
-
 // marshalExemplarJSON writes.
 //
 //	{
@@ -201,10 +212,6 @@ func marshalExemplarJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	stream.WriteObjectEnd()
 }
 
-func marshalExemplarJSONEmpty(unsafe.Pointer) bool {
-	return false
-}
-
 func unsafeMarshalLabelsJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	labelsPtr := (*labels.Labels)(ptr)
 	marshalLabelsJSON(*labelsPtr, stream)
@@ -229,3 +236,23 @@ func labelsIsEmpty(ptr unsafe.Pointer) bool {
 	labelsPtr := (*labels.Labels)(ptr)
 	return labelsPtr.IsEmpty()
 }
+
+// Marshal a Vector as `[sample,sample,...]` - empty Vector is `[]`.
+func unsafeMarshalVectorJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+	v := *((*promql.Vector)(ptr))
+	stream.WriteArrayStart()
+	for _, s := range v {
+		marshalSampleJSON(s, stream)
+	}
+	stream.WriteArrayEnd()
+}
+
+// Marshal a Matrix as `[series,series,...]` - empty Matrix is `[]`.
+func unsafeMarshalMatrixJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+	m := *((*promql.Matrix)(ptr))
+	stream.WriteArrayStart()
+	for _, s := range m {
+		marshalSeriesJSON(s, stream)
+	}
+	stream.WriteArrayEnd()
+}