/
instrumentation.go
55 lines (44 loc) · 1.66 KB
/
instrumentation.go
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package trarelic
import (
"net/http"
)
// NewRoundTripper creates http.RoundTripper to instrument external requests.
// The RoundTripper returned creates an external span with tags (or use existed one) before delegating to the original
// RoundTripper provided (or http.DefaultTransport if none is provided).
func NewRoundTripper(original http.RoundTripper, opts ...TrarelicOption) http.RoundTripper {
settings := NewTrarelic(opts...)
return roundTripperFunc(func(request *http.Request) (*http.Response, error) {
// The specification of http.RoundTripper requires that the request is never modified.
// And though we don't need the modification right now, in the future this could be useful.
request = cloneRequest(request)
if nil == original {
original = http.DefaultTransport
}
span := settings.GetSpanFromRequest(request)
if span != nil {
span.SetTag("is_external", true)
span.SetTag("type", settings.Type)
span.SetTag("caller", settings.Caller)
}
response, err := original.RoundTrip(request)
if span != nil && settings.NewSpan {
span.Finish()
}
return response, err
})
}
// cloneRequest mimics implementation of
// https://godoc.org/github.com/google/go-github/github#BasicAuthTransport.RoundTrip
func cloneRequest(r *http.Request) *http.Request {
// shallow copy of the struct
r2 := new(http.Request)
*r2 = *r
// deep copy of the Header
r2.Header = make(http.Header, len(r.Header))
for k, s := range r.Header {
r2.Header[k] = append([]string(nil), s...)
}
return r2
}
type roundTripperFunc func(*http.Request) (*http.Response, error)
func (f roundTripperFunc) RoundTrip(r *http.Request) (*http.Response, error) { return f(r) }