Merge pull request #718 from gotjosh/support-metric-metadata-endpoint

API Client: Support new metadata endpoint in v1

api/prometheus/v1/api.go

@@ -130,6 +130,7 @@ const (
 	epSeries          = apiPrefix + "/series"
 	epTargets         = apiPrefix + "/targets"
 	epTargetsMetadata = apiPrefix + "/targets/metadata"
+	epMetadata        = apiPrefix + "/metadata"
 	epRules           = apiPrefix + "/rules"
 	epSnapshot        = apiPrefix + "/admin/tsdb/snapshot"
 	epDeleteSeries    = apiPrefix + "/admin/tsdb/delete_series"
@@ -248,6 +249,8 @@ type API interface {
 	Targets(ctx context.Context) (TargetsResult, error)
 	// TargetsMetadata returns metadata about metrics currently scraped by the target.
 	TargetsMetadata(ctx context.Context, matchTarget string, metric string, limit string) ([]MetricMetadata, error)
+	// Metadata returns metadata about metrics currently scraped by the metric name.
+	Metadata(ctx context.Context, metric string, limit string) (map[string][]Metadata, error)
 }
 
 // AlertsResult contains the result from querying the alerts endpoint.
@@ -357,7 +360,7 @@ type DroppedTarget struct {
 	DiscoveredLabels map[string]string `json:"discoveredLabels"`
 }
 
-// MetricMetadata models the metadata of a metric.
+// MetricMetadata models the metadata of a metric with its scrape target and name.
 type MetricMetadata struct {
 	Target map[string]string `json:"target"`
 	Metric string            `json:"metric,omitempty"`
@@ -366,6 +369,13 @@ type MetricMetadata struct {
 	Unit   string            `json:"unit"`
 }
 
+// Metadata models the metadata of a metric.
+type Metadata struct {
+	Type MetricType `json:"type"`
+	Help string     `json:"help"`
+	Unit string     `json:"unit"`
+}
+
 // queryResult contains result data for a query.
 type queryResult struct {
 	Type   model.ValueType `json:"resultType"`
@@ -802,6 +812,29 @@ func (h *httpAPI) TargetsMetadata(ctx context.Context, matchTarget string, metri
 	return res, json.Unmarshal(body, &res)
 }
 
+func (h *httpAPI) Metadata(ctx context.Context, metric string, limit string) (map[string][]Metadata, error) {
+	u := h.client.URL(epMetadata, nil)
+	q := u.Query()
+
+	q.Set("metric", metric)
+	q.Set("limit", limit)
+
+	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 map[string][]Metadata
+	return res, json.Unmarshal(body, &res)
+}
+
 // Warnings is an array of non critical errors
 type Warnings []string
 

api/prometheus/v1/api_test.go

@@ -202,6 +202,13 @@ func TestAPIs(t *testing.T) {
 		}
 	}
 
+	doMetadata := func(metric string, limit string) func() (interface{}, Warnings, error) {
+		return func() (interface{}, Warnings, error) {
+			v, err := promAPI.Metadata(context.Background(), metric, limit)
+			return v, nil, err
+		}
+	}
+
 	queryTests := []apiTest{
 		{
 			do: doQuery("2", testTime),
@@ -857,6 +864,46 @@ func TestAPIs(t *testing.T) {
 			},
 			err: fmt.Errorf("some error"),
 		},
+
+		{
+			do: doMetadata("go_goroutines", "1"),
+			inRes: map[string]interface{}{
+				"go_goroutines": []map[string]interface{}{
+					{
+						"type": "gauge",
+						"help": "Number of goroutines that currently exist.",
+						"unit": "",
+					},
+				},
+			},
+			reqMethod: "GET",
+			reqPath:   "/api/v1/metadata",
+			reqParam: url.Values{
+				"metric": []string{"go_goroutines"},
+				"limit":  []string{"1"},
+			},
+			res: map[string][]Metadata{
+				"go_goroutines": []Metadata{
+					{
+						Type: "gauge",
+						Help: "Number of goroutines that currently exist.",
+						Unit: "",
+					},
+				},
+			},
+		},
+
+		{
+			do:        doMetadata("", "1"),
+			inErr:     fmt.Errorf("some error"),
+			reqMethod: "GET",
+			reqPath:   "/api/v1/metadata",
+			reqParam: url.Values{
+				"metric": []string{""},
+				"limit":  []string{"1"},
+			},
+			err: fmt.Errorf("some error"),
+		},
 	}
 
 	var tests []apiTest