web/api: replace /metrics/names with /label/:name/values endpoint.

web/api/v1/api.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"golang.org/x/net/context"
 
 	clientmodel "github.com/prometheus/client_golang/model"
 
@@ -29,7 +30,8 @@ const (
 type errorType string
 
 const (
-	errorTimeout  errorType = "timeout"
+	errorNone     errorType = ""
+	errorTimeout            = "timeout"
 	errorCanceled           = "canceled"
 	errorExec               = "execution"
 	errorBadData            = "bad_data"
@@ -56,6 +58,8 @@ type response struct {
 type API struct {
 	Storage     local.Storage
 	QueryEngine *promql.Engine
+
+	context func(r *http.Request) context.Context
 }
 
 // Enables cross-site script calls.
@@ -70,6 +74,10 @@ type apiFunc func(r *http.Request) (interface{}, *apiError)
 
 // Register the API's endpoints in the given router.
 func (api *API) Register(r *route.Router) {
+	if api.context == nil {
+		api.context = route.Context
+	}
+
 	instr := func(name string, f apiFunc) http.HandlerFunc {
 		return prometheus.InstrumentHandlerFunc(name, func(w http.ResponseWriter, r *http.Request) {
 			setCORS(w)
@@ -84,7 +92,7 @@ func (api *API) Register(r *route.Router) {
 	r.Get("/query", instr("query", api.query))
 	r.Get("/query_range", instr("query_range", api.queryRange))
 
-	r.Get("/metrics/names", instr("metric_names", api.metricNames))
+	r.Get("/label/:name/values", instr("label_values", api.labelValues))
 }
 
 type queryData struct {
@@ -154,11 +162,16 @@ func (api *API) queryRange(r *http.Request) (interface{}, *apiError) {
 	}, nil
 }
 
-func (api *API) metricNames(r *http.Request) (interface{}, *apiError) {
-	metricNames := api.Storage.LabelValuesForLabelName(clientmodel.MetricNameLabel)
-	sort.Sort(metricNames)
+func (api *API) labelValues(r *http.Request) (interface{}, *apiError) {
+	name := route.Param(api.context(r), "name")
+
+	if !clientmodel.LabelNameRE.MatchString(name) {
+		return nil, &apiError{errorBadData, fmt.Errorf("invalid label name: %q", name)}
+	}
+	vals := api.Storage.LabelValuesForLabelName(clientmodel.LabelName(name))
+	sort.Sort(vals)
 
-	return metricNames, nil
+	return vals, nil
 }
 
 func respond(w http.ResponseWriter, data interface{}) {

web/api/v1/api_test.go

@@ -11,9 +11,12 @@ import (
 	"testing"
 	"time"
 
+	"golang.org/x/net/context"
+
 	clientmodel "github.com/prometheus/client_golang/model"
 
 	"github.com/prometheus/prometheus/promql"
+	"github.com/prometheus/prometheus/util/route"
 )
 
 func TestEndpoints(t *testing.T) {
@@ -40,6 +43,7 @@ func TestEndpoints(t *testing.T) {
 	start := clientmodel.Timestamp(0)
 	var tests = []struct {
 		endpoint apiFunc
+		params   map[string]string
 		query    url.Values
 		response interface{}
 		errType  errorType
@@ -87,30 +91,59 @@ func TestEndpoints(t *testing.T) {
 			},
 		},
 		{
-			endpoint: api.metricNames,
+			endpoint: api.labelValues,
+			params: map[string]string{
+				"name": "__name__",
+			},
 			response: clientmodel.LabelValues{
 				"test_metric1",
 				"test_metric2",
 			},
 		},
+		{
+			endpoint: api.labelValues,
+			params: map[string]string{
+				"name": "not!!!allowed",
+			},
+			errType: errorBadData,
+		},
+		{
+			endpoint: api.labelValues,
+			params: map[string]string{
+				"name": "foo",
+			},
+			response: clientmodel.LabelValues{
+				"bar",
+				"boo",
+			},
+		},
 	}
 
 	for _, test := range tests {
+		// Build a context with the correct request params.
+		ctx := context.Background()
+		for p, v := range test.params {
+			ctx = route.WithParam(ctx, p, v)
+		}
+		api.context = func(r *http.Request) context.Context {
+			return ctx
+		}
+
 		req, err := http.NewRequest("ANY", fmt.Sprintf("http://example.com?%s", test.query.Encode()), nil)
 		if err != nil {
 			t.Fatal(err)
 		}
-		resp, apierr := test.endpoint(req)
-		if apierr != nil {
-			if test.errType == "" {
-				t.Fatalf("Unexpected error: %s", apierr)
+		resp, apiErr := test.endpoint(req)
+		if apiErr != nil {
+			if test.errType == errorNone {
+				t.Fatalf("Unexpected error: %s", apiErr)
 			}
-			if test.errType != apierr.typ {
-				t.Fatalf("Expected error of type %q but got type %q", test.errType, apierr.typ)
+			if test.errType != apiErr.typ {
+				t.Fatalf("Expected error of type %q but got type %q", test.errType, apiErr.typ)
 			}
 			continue
 		}
-		if apierr == nil && test.errType != "" {
+		if apiErr == nil && test.errType != errorNone {
 			t.Fatalf("Expected error of type %q but got none", test.errType)
 		}
 		if !reflect.DeepEqual(resp, test.response) {