micro/api/handler/web/web.go

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// Package web contains the web handler including websocket support
package web
import (
"errors"
"fmt"
"io"
"net"
"net/http"
"net/http/httputil"
"net/url"
"strings"
"github.com/micro/go-micro/api"
"github.com/micro/go-micro/api/handler"
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"github.com/micro/go-micro/client/selector"
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)
const (
Handler = "web"
)
type webHandler struct {
opts handler.Options
s *api.Service
}
func (wh *webHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
service, err := wh.getService(r)
if err != nil {
w.WriteHeader(500)
return
}
if len(service) == 0 {
w.WriteHeader(404)
return
}
rp, err := url.Parse(service)
if err != nil {
w.WriteHeader(500)
return
}
if isWebSocket(r) {
wh.serveWebSocket(rp.Host, w, r)
return
}
httputil.NewSingleHostReverseProxy(rp).ServeHTTP(w, r)
}
// getService returns the service for this request from the selector
func (wh *webHandler) getService(r *http.Request) (string, error) {
var service *api.Service
if wh.s != nil {
// we were given the service
service = wh.s
} else if wh.opts.Router != nil {
// try get service from router
s, err := wh.opts.Router.Route(r)
if err != nil {
return "", err
}
service = s
} else {
// we have no way of routing the request
return "", errors.New("no route found")
}
// create a random selector
next := selector.Random(service.Services)
// get the next node
s, err := next()
if err != nil {
return "", nil
}
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return fmt.Sprintf("http://%s", s.Address), nil
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}
// serveWebSocket used to serve a web socket proxied connection
func (wh *webHandler) serveWebSocket(host string, w http.ResponseWriter, r *http.Request) {
req := new(http.Request)
*req = *r
if len(host) == 0 {
http.Error(w, "invalid host", 500)
return
}
// set x-forward-for
if clientIP, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
if ips, ok := req.Header["X-Forwarded-For"]; ok {
clientIP = strings.Join(ips, ", ") + ", " + clientIP
}
req.Header.Set("X-Forwarded-For", clientIP)
}
// connect to the backend host
conn, err := net.Dial("tcp", host)
if err != nil {
http.Error(w, err.Error(), 500)
return
}
// hijack the connection
hj, ok := w.(http.Hijacker)
if !ok {
http.Error(w, "failed to connect", 500)
return
}
nc, _, err := hj.Hijack()
if err != nil {
return
}
defer nc.Close()
defer conn.Close()
if err = req.Write(conn); err != nil {
return
}
errCh := make(chan error, 2)
cp := func(dst io.Writer, src io.Reader) {
_, err := io.Copy(dst, src)
errCh <- err
}
go cp(conn, nc)
go cp(nc, conn)
<-errCh
}
func isWebSocket(r *http.Request) bool {
contains := func(key, val string) bool {
vv := strings.Split(r.Header.Get(key), ",")
for _, v := range vv {
if val == strings.ToLower(strings.TrimSpace(v)) {
return true
}
}
return false
}
if contains("Connection", "upgrade") && contains("Upgrade", "websocket") {
return true
}
return false
}
func (wh *webHandler) String() string {
return "web"
}
func NewHandler(opts ...handler.Option) handler.Handler {
return &webHandler{
opts: handler.NewOptions(opts...),
}
}
func WithService(s *api.Service, opts ...handler.Option) handler.Handler {
options := handler.NewOptions(opts...)
return &webHandler{
opts: options,
s: s,
}
}