add exemplars API support

Signed-off-by: yeya24 <yb532204897@gmail.com>

api/prometheus/v1/api.go

@@ -123,6 +123,7 @@ const (
 	epAlertManagers   = apiPrefix + "/alertmanagers"
 	epQuery           = apiPrefix + "/query"
 	epQueryRange      = apiPrefix + "/query_range"
+	epQueryExemplars  = apiPrefix + "/query_exemplars"
 	epLabels          = apiPrefix + "/labels"
 	epLabelValues     = apiPrefix + "/label/:name/values"
 	epSeries          = apiPrefix + "/series"
@@ -239,6 +240,8 @@ type API interface {
 	Query(ctx context.Context, query string, ts time.Time) (model.Value, Warnings, error)
 	// QueryRange performs a query for the given range.
 	QueryRange(ctx context.Context, query string, r Range) (model.Value, Warnings, error)
+	// QueryExemplars performs a query for exemplars by the given query and time range.
+	QueryExemplars(ctx context.Context, query string, startTime time.Time, endTime time.Time) ([]ExemplarQueryResult, error)
 	// Buildinfo returns various build information properties about the Prometheus server
 	Buildinfo(ctx context.Context) (BuildinfoResult, error)
 	// Runtimeinfo returns the various runtime information properties about the Prometheus server.
@@ -588,6 +591,18 @@ func (qr *queryResult) UnmarshalJSON(b []byte) error {
 	return err
 }
 
+// Exemplar is additional information associated with a time series.
+type Exemplar struct {
+	Labels    model.LabelSet    `json:"labels"`
+	Value     model.SampleValue `json:"value"`
+	Timestamp model.Time        `json:"timestamp"`
+}
+
+type ExemplarQueryResult struct {
+	SeriesLabels model.LabelSet `json:"seriesLabels"`
+	Exemplars    []Exemplar     `json:"exemplars"`
+}
+
 // NewAPI returns a new API for the client.
 //
 // It is safe to use the returned API from multiple goroutines.
@@ -967,7 +982,29 @@ func (h *httpAPI) TSDB(ctx context.Context) (TSDBResult, error) {
 
 	var res TSDBResult
 	return res, json.Unmarshal(body, &res)
+}
 
+func (h *httpAPI) QueryExemplars(ctx context.Context, query string, startTime time.Time, endTime time.Time) ([]ExemplarQueryResult, error) {
+	u := h.client.URL(epQueryExemplars, nil)
+	q := u.Query()
+
+	q.Set("query", query)
+	q.Set("start", formatTime(startTime))
+	q.Set("end", formatTime(endTime))
+	u.RawQuery = q.Encode()
+
+	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+
+	_, body, _, err := h.client.Do(ctx, req)
+	if err != nil {
+		return nil, err
+	}
+
+	var res []ExemplarQueryResult
+	return res, json.Unmarshal(body, &res)
 }
 
 // Warnings is an array of non critical errors

api/prometheus/v1/api_test.go

@@ -230,6 +230,13 @@ func TestAPIs(t *testing.T) {
 		}
 	}
 
+	doQueryExemplars := func(query string, startTime time.Time, endTime time.Time) func() (interface{}, Warnings, error) {
+		return func() (interface{}, Warnings, error) {
+			v, err := promAPI.QueryExemplars(context.Background(), query, startTime, endTime)
+			return v, nil, err
+		}
+	}
+
 	queryTests := []apiTest{
 		{
 			do: doQuery("2", testTime),
@@ -1190,6 +1197,66 @@ func TestAPIs(t *testing.T) {
 				},
 			},
 		},
+
+		{
+			do:        doQueryExemplars("tns_request_duration_seconds_bucket", testTime.Add(-1*time.Minute), testTime),
+			reqMethod: "GET",
+			reqPath:   "/api/v1/query_exemplars",
+			inErr:     fmt.Errorf("some error"),
+			err:       fmt.Errorf("some error"),
+		},
+
+		{
+			do:        doQueryExemplars("tns_request_duration_seconds_bucket", testTime.Add(-1*time.Minute), testTime),
+			reqMethod: "GET",
+			reqPath:   "/api/v1/query_exemplars",
+			inRes: []interface{}{
+				map[string]interface{}{
+					"seriesLabels": map[string]interface{}{
+						"__name__": "tns_request_duration_seconds_bucket",
+						"instance": "app:80",
+						"job":      "tns/app",
+					},
+					"exemplars": []interface{}{
+						map[string]interface{}{
+							"labels": map[string]interface{}{
+								"traceID": "19fd8c8a33975a23",
+							},
+							"value":     "0.003863295",
+							"timestamp": model.TimeFromUnixNano(testTime.UnixNano()),
+						},
+						map[string]interface{}{
+							"labels": map[string]interface{}{
+								"traceID": "67f743f07cc786b0",
+							},
+							"value":     "0.001535405",
+							"timestamp": model.TimeFromUnixNano(testTime.UnixNano()),
+						},
+					},
+				},
+			},
+			res: []ExemplarQueryResult{
+				{
+					SeriesLabels: model.LabelSet{
+						"__name__": "tns_request_duration_seconds_bucket",
+						"instance": "app:80",
+						"job":      "tns/app",
+					},
+					Exemplars: []Exemplar{
+						{
+							Labels:    model.LabelSet{"traceID": "19fd8c8a33975a23"},
+							Value:     0.003863295,
+							Timestamp: model.TimeFromUnixNano(testTime.UnixNano()),
+						},
+						{
+							Labels:    model.LabelSet{"traceID": "67f743f07cc786b0"},
+							Value:     0.001535405,
+							Timestamp: model.TimeFromUnixNano(testTime.UnixNano()),
+						},
+					},
+				},
+			},
+		},
 	}
 
 	var tests []apiTest