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downstream_roundtripper.go
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downstream_roundtripper.go
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/*
* Copyright (C) 2023 Intergral GmbH
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package frontend
import (
"net/http"
"net/url"
"path"
"github.com/opentracing/opentracing-go"
)
// RoundTripper that forwards requests to downstream URL.
type downstreamRoundTripper struct {
downstreamURL *url.URL
transport http.RoundTripper
}
func NewDownstreamRoundTripper(downstreamURL string, transport http.RoundTripper) (http.RoundTripper, error) {
u, err := url.Parse(downstreamURL)
if err != nil {
return nil, err
}
return &downstreamRoundTripper{downstreamURL: u, transport: transport}, nil
}
func (d downstreamRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
tracer, span := opentracing.GlobalTracer(), opentracing.SpanFromContext(r.Context())
if tracer != nil && span != nil {
carrier := make(opentracing.TextMapCarrier, len(r.Header))
for k, v := range r.Header {
carrier.Set(k, v[0])
}
err := tracer.Inject(span.Context(), opentracing.TextMap, carrier)
if err != nil {
return nil, err
}
}
r.URL.Scheme = d.downstreamURL.Scheme
r.URL.Host = d.downstreamURL.Host
r.URL.Path = path.Join(d.downstreamURL.Path, r.URL.Path)
r.Host = ""
return d.transport.RoundTrip(r)
}