Use common/expfmt in federation

web/federate.go

@@ -1,18 +1,15 @@
 package web
 
 import (
-	"io"
 	"net/http"
 
-	"bitbucket.org/ww/goautoneg"
 	"github.com/golang/protobuf/proto"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/text"
 
 	"github.com/prometheus/prometheus/promql"
 	"github.com/prometheus/prometheus/storage/local"
 
 	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
 	"github.com/prometheus/common/model"
 )
 
@@ -36,8 +33,10 @@ func (fed *Federation) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		}
 	}
 
-	enc, contentType := chooseEncoder(req)
+	format := expfmt.Negotiate(req.Header)
-	w.Header().Set("Content-Type", contentType)
+	w.Header().Set("Content-Type", string(format))
+
+	enc := expfmt.NewEncoder(w, format)
 
 	protMetric := &dto.Metric{
 		Label:   []*dto.LabelPair{},
@@ -70,39 +69,10 @@ func (fed *Federation) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		protMetric.TimestampMs = (*int64)(&sp.Timestamp)
 		protMetric.Untyped.Value = (*float64)(&sp.Value)
 
-		if _, err := enc(w, protMetricFam); err != nil {
+		if err := enc.Encode(protMetricFam); err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
-		}
-	}
-}
 
-type encoder func(w io.Writer, p *dto.MetricFamily) (int, error)
-
-func chooseEncoder(req *http.Request) (encoder, string) {
-	accepts := goautoneg.ParseAccept(req.Header.Get("Accept"))
-	for _, accept := range accepts {
-		switch {
-		case accept.Type == "application" &&
-			accept.SubType == "vnd.google.protobuf" &&
-			accept.Params["proto"] == "io.prometheus.client.MetricFamily":
-			switch accept.Params["encoding"] {
-			case "delimited":
-				return text.WriteProtoDelimited, prometheus.DelimitedTelemetryContentType
-			case "text":
-				return text.WriteProtoText, prometheus.ProtoTextTelemetryContentType
-			case "compact-text":
-				return text.WriteProtoCompactText, prometheus.ProtoCompactTextTelemetryContentType
-			default:
-				continue
-			}
-		case accept.Type == "text" &&
-			accept.SubType == "plain" &&
-			(accept.Params["version"] == "0.0.4" || accept.Params["version"] == ""):
-			return text.MetricFamilyToText, prometheus.TextTelemetryContentType
-		default:
-			continue
 		}
 	}
-	return text.MetricFamilyToText, prometheus.TextTelemetryContentType
 }