Skip to content
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
199 lines (178 sloc) 5.59 KB
// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
package apmhttp
import (
// WrapClient returns a new *http.Client with all fields copied
// across, and the Transport field wrapped with WrapRoundTripper
// such that client requests are reported as spans to Elastic APM
// if their context contains a sampled transaction.
// Spans are started just before the request is sent, and ended
// immediately if the request returned an error (e.g. due to socket
// timeout, but not a valid response with a non-200 status code),
// or otherwise when the response body is fully consumed or closed.
// If c is nil, then http.DefaultClient is wrapped.
func WrapClient(c *http.Client, o ...ClientOption) *http.Client {
if c == nil {
c = http.DefaultClient
copied := *c
copied.Transport = WrapRoundTripper(copied.Transport, o...)
return &copied
// WrapRoundTripper returns an http.RoundTripper wrapping r, reporting each
// request as a span to Elastic APM, if the request's context contains a
// sampled transaction.
// If r is nil, then http.DefaultTransport is wrapped.
func WrapRoundTripper(r http.RoundTripper, o ...ClientOption) http.RoundTripper {
if r == nil {
r = http.DefaultTransport
rt := &roundTripper{
r: r,
requestName: ClientRequestName,
requestIgnorer: IgnoreNone,
for _, o := range o {
return rt
type roundTripper struct {
r http.RoundTripper
requestName RequestNameFunc
requestIgnorer RequestIgnorerFunc
// RoundTrip delegates to r.r, emitting a span if req's context
// contains a transaction.
func (r *roundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
// TODO(axw) propagate Tracestate, adding/shifting the elastic
// key to the left most position.
if r.requestIgnorer(req) {
return r.r.RoundTrip(req)
ctx := req.Context()
tx := apm.TransactionFromContext(ctx)
if tx == nil {
return r.r.RoundTrip(req)
// RoundTrip is not supposed to mutate req, so copy req
// and set the trace-context headers only in the copy.
reqCopy := *req
reqCopy.Header = make(http.Header, len(req.Header))
for k, v := range req.Header {
reqCopy.Header[k] = v
req = &reqCopy
propagateLegacyHeader := tx.ShouldPropagateLegacyHeader()
traceContext := tx.TraceContext()
if !traceContext.Options.Recorded() {
r.setHeaders(req, traceContext, propagateLegacyHeader)
return r.r.RoundTrip(req)
name := r.requestName(req)
span := tx.StartSpan(name, "external.http", apm.SpanFromContext(ctx))
if !span.Dropped() {
traceContext = span.TraceContext()
ctx = apm.ContextWithSpan(ctx, span)
req = RequestWithContext(ctx, req)
} else {
span = nil
r.setHeaders(req, traceContext, propagateLegacyHeader)
resp, err := r.r.RoundTrip(req)
if span != nil {
if err != nil {
} else {
resp.Body = &responseBody{span: span, body: resp.Body}
return resp, err
func (r *roundTripper) setHeaders(req *http.Request, traceContext apm.TraceContext, propagateLegacyHeader bool) {
headerValue := FormatTraceparentHeader(traceContext)
if propagateLegacyHeader {
req.Header.Set(ElasticTraceparentHeader, headerValue)
req.Header.Set(W3CTraceparentHeader, headerValue)
// CloseIdleConnections calls r.r.CloseIdleConnections if the method exists.
func (r *roundTripper) CloseIdleConnections() {
type closeIdler interface {
if r, ok := r.r.(closeIdler); ok {
// CancelRequest calls r.r.CancelRequest(req) if the method exists.
func (r *roundTripper) CancelRequest(req *http.Request) {
type cancelRequester interface {
if r, ok := r.r.(cancelRequester); ok {
type responseBody struct {
span *apm.Span
body io.ReadCloser
// Close closes the response body, and ends the span if it hasn't already been ended.
func (b *responseBody) Close() error {
return b.body.Close()
// Read reads from the response body, and ends the span when io.EOF is returend if
// the span hasn't already been ended.
func (b *responseBody) Read(p []byte) (n int, err error) {
n, err = b.body.Read(p)
if err == io.EOF {
return n, err
func (b *responseBody) endSpan() {
addr := (*unsafe.Pointer)(unsafe.Pointer(&b.span))
if old := atomic.SwapPointer(addr, nil); old != nil {
// ClientOption sets options for tracing client requests.
type ClientOption func(*roundTripper)
// WithClientRequestName returns a ClientOption which sets r as the function
// to use to obtain the span name for the given http request.
func WithClientRequestName(r RequestNameFunc) ClientOption {
if r == nil {
panic("r == nil")
return ClientOption(func(rt *roundTripper) {
rt.requestName = r
You can’t perform that action at this time.