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roundtripper.go
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/
roundtripper.go
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// Unless explicitly stated otherwise all files in this repository are licensed
// under the Apache License Version 2.0.
// This product includes software developed at Datadog (https://www.datadoghq.com/).
// Copyright 2016 Datadog, Inc.
package http
import (
"fmt"
"math"
"net/http"
"os"
"strconv"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
)
type roundTripper struct {
base http.RoundTripper
cfg *roundTripperConfig
}
func (rt *roundTripper) RoundTrip(req *http.Request) (res *http.Response, err error) {
resourceName := rt.cfg.resourceNamer(req)
opts := []ddtrace.StartSpanOption{
tracer.SpanType(ext.SpanTypeHTTP),
tracer.ResourceName(resourceName),
tracer.Tag(ext.HTTPMethod, req.Method),
tracer.Tag(ext.HTTPURL, req.URL.Path),
}
if !math.IsNaN(rt.cfg.analyticsRate) {
opts = append(opts, tracer.Tag(ext.EventSampleRate, rt.cfg.analyticsRate))
}
if rt.cfg.serviceName != "" {
opts = append(opts, tracer.ServiceName(rt.cfg.serviceName))
}
span, ctx := tracer.StartSpanFromContext(req.Context(), "http.request", opts...)
defer func() {
if rt.cfg.after != nil {
rt.cfg.after(res, span)
}
span.Finish(tracer.WithError(err))
}()
if rt.cfg.before != nil {
rt.cfg.before(req, span)
}
// inject the span context into the http request
err = tracer.Inject(span.Context(), tracer.HTTPHeadersCarrier(req.Header))
if err != nil {
// this should never happen
fmt.Fprintf(os.Stderr, "contrib/net/http.Roundtrip: failed to inject http headers: %v\n", err)
}
res, err = rt.base.RoundTrip(req.WithContext(ctx))
if err != nil {
span.SetTag("http.errors", err.Error())
span.SetTag(ext.Error, err)
} else {
span.SetTag(ext.HTTPCode, strconv.Itoa(res.StatusCode))
// treat 5XX as errors
if res.StatusCode/100 == 5 {
span.SetTag("http.errors", res.Status)
span.SetTag(ext.Error, fmt.Errorf("%d: %s", res.StatusCode, http.StatusText(res.StatusCode)))
}
}
return res, err
}
// Unwrap returns the original http.RoundTripper.
func (rt *roundTripper) Unwrap() http.RoundTripper {
return rt.base
}
// WrapRoundTripper returns a new RoundTripper which traces all requests sent
// over the transport.
func WrapRoundTripper(rt http.RoundTripper, opts ...RoundTripperOption) http.RoundTripper {
cfg := newRoundTripperConfig()
for _, opt := range opts {
opt(cfg)
}
if wrapped, ok := rt.(*roundTripper); ok {
rt = wrapped.base
}
return &roundTripper{
base: rt,
cfg: cfg,
}
}
// WrapClient modifies the given client's transport to augment it with tracing and returns it.
func WrapClient(c *http.Client, opts ...RoundTripperOption) *http.Client {
if c.Transport == nil {
c.Transport = http.DefaultTransport
}
c.Transport = WrapRoundTripper(c.Transport, opts...)
return c
}