func chooseEncoder(req *http.Request) (encoder, string) {
accepts := goautoneg.ParseAccept(req.Header.Get(acceptHeader))
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, DelimitedTelemetryContentType
case "text":
return text.WriteProtoText, ProtoTextTelemetryContentType
case "compact-text":
return text.WriteProtoCompactText, ProtoCompactTextTelemetryContentType
default:
continue
}
case accept.Type == "text" &&
accept.SubType == "plain" &&
(accept.Params["version"] == "0.0.4" || accept.Params["version"] == ""):
return text.MetricFamilyToText, TextTelemetryContentType
default:
continue
}
}
return text.MetricFamilyToText, TextTelemetryContentType
}
// Negotiate returns the Content-Type based on the given Accept header.
// If no appropriate accepted type is found, FmtText is returned.
func Negotiate(h http.Header) Format {
for _, ac := range goautoneg.ParseAccept(h.Get(hdrAccept)) {
// Check for protocol buffer
if ac.Type+"/"+ac.SubType == ProtoType && ac.Params["proto"] == ProtoProtocol {
switch ac.Params["encoding"] {
case "delimited":
return FmtProtoDelim
case "text":
return FmtProtoText
case "compact-text":
return FmtProtoCompact
}
}
// Check for text format.
ver := ac.Params["version"]
if ac.Type == "text" && ac.SubType == "plain" && (ver == TextVersion || ver == "") {
return FmtText
}
}
return FmtText
}