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package main
import (
"fmt"
"io"
"strings"
"net"
"net/http"
"net/url"
log "github.com/sirupsen/logrus"
)
func main() {
const addr = "localhost:3333"
log.Info("configuring reverse proxy...")
configureEndpoint("/proxy1", "http://localhost:8000")
log.Infof("serving on %v", addr)
log.Fatal(http.ListenAndServe(addr, nil))
}
type Endpoint struct {
Path string
Origin *url.URL
}
func configureEndpoint(path, address string) {
log.Infof("proxying endpoint %v to %v", path, address)
origin, err := url.Parse(address)
if err != nil {
log.Fatal(err)
}
end := Endpoint{
Path: path,
Origin: origin,
}
http.HandleFunc(path + "/", func(w http.ResponseWriter, req *http.Request) {
log.Infof("REQ: %v", req.URL.Path)
proxy(w, req, end)
})
}
func proxy(w http.ResponseWriter, req *http.Request, end Endpoint) {
response := proxyRequest(w, req, end)
proxyResponse(w, response)
}
func proxyRequest(w http.ResponseWriter, req *http.Request, end Endpoint) *http.Response {
// configure host address
req.Host = end.Origin.Host
req.URL.Host = end.Origin.Host
// strip proxy endpoint path from request path
req.URL.Path = strings.TrimPrefix(req.URL.Path, end.Path)
// set X-Forwarded-For
forwardedFor, _, _ := net.SplitHostPort(req.RemoteAddr)
req.Header.Set("X-Forwarded-For", forwardedFor)
// misc request cleanups
req.URL.Scheme = end.Origin.Scheme
req.RequestURI = ""
// make request
response, err := http.DefaultClient.Do(req)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "%v", err)
log.Fatal(err)
}
return response
}
func proxyResponse(w http.ResponseWriter, response *http.Response) {
// copy header
for key, values := range response.Header {
for _, value := range values {
w.Header().Add(key, value)
}
}
// get trailer keys
trailerKeys := []string{}
for key := range response.Trailer {
trailerKeys = append(trailerKeys, key)
}
if (len(trailerKeys) > 0) {
w.Header().Set("Trailer", strings.Join(trailerKeys, ","))
}
w.WriteHeader(response.StatusCode)
// copy body to client
io.Copy(w, response.Body)
// write trailers
for key, values := range response.Trailer {
for _, value := range values {
w.Header().Set(key, value)
}
}
}
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