client_golang/prometheus/exp/responsewriter_delegator.go

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// Copyright (c) 2013, Prometheus Team
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
package exp
import (
"fmt"
"net/http"
"reflect"
"strconv"
)
const (
unknownStatusCode = "unknown"
statusFieldName = "status"
)
type status string
func (s status) unknown() bool {
return len(s) == 0
}
func (s status) String() string {
if s.unknown() {
return unknownStatusCode
}
return string(s)
}
func computeApproximateRequestSize(r http.Request) (s int) {
s += len(r.Method)
if r.URL != nil {
s += len(r.URL.String())
}
s += len(r.Proto)
for name, values := range r.Header {
s += len(name)
for _, value := range values {
s += len(value)
}
}
s += len(r.Host)
// N.B. r.Form and r.MultipartForm are assumed to be included in r.URL.
if r.ContentLength != -1 {
s += int(r.ContentLength)
}
return
}
// ResponseWriterDelegator is a means of wrapping http.ResponseWriter to divine
// the response code from a given answer, especially in systems where the
// response is treated as a blackbox.
type ResponseWriterDelegator struct {
http.ResponseWriter
status status
BytesWritten int
}
func (r ResponseWriterDelegator) String() string {
return fmt.Sprintf("ResponseWriterDelegator decorating %s with status %s and %d bytes written.", r.ResponseWriter, r.status, r.BytesWritten)
}
func (r *ResponseWriterDelegator) WriteHeader(code int) {
r.status = status(strconv.Itoa(code))
r.ResponseWriter.WriteHeader(code)
}
func (r *ResponseWriterDelegator) Status() string {
if r.status.unknown() {
delegate := reflect.ValueOf(r.ResponseWriter).Elem()
statusField := delegate.FieldByName(statusFieldName)
if statusField.IsValid() {
r.status = status(strconv.Itoa(int(statusField.Int())))
}
}
return r.status.String()
}
func (r *ResponseWriterDelegator) Write(b []byte) (n int, err error) {
n, err = r.ResponseWriter.Write(b)
r.BytesWritten += n
return
}
func NewResponseWriterDelegator(delegate http.ResponseWriter) *ResponseWriterDelegator {
return &ResponseWriterDelegator{
ResponseWriter: delegate,
}
}