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package middleware
import (
"errors"
"fmt"
"io"
"math/rand"
"net"
"net/http"
"net/http/httputil"
"net/url"
"sync/atomic"
"time"
"github.com/labstack/echo"
)
// TODO: Handle TLS proxy
type (
// ProxyConfig defines the config for Proxy middleware.
ProxyConfig struct {
// Skipper defines a function to skip middleware.
Skipper Skipper
// Balancer defines a load balancing technique.
// Required.
// Possible values:
// - RandomBalancer
// - RoundRobinBalancer
Balancer ProxyBalancer
}
// ProxyTarget defines the upstream target.
ProxyTarget struct {
URL *url.URL
}
// RandomBalancer implements a random load balancing technique.
RandomBalancer struct {
Targets []*ProxyTarget
random *rand.Rand
}
// RoundRobinBalancer implements a round-robin load balancing technique.
RoundRobinBalancer struct {
Targets []*ProxyTarget
i uint32
}
// ProxyBalancer defines an interface to implement a load balancing technique.
ProxyBalancer interface {
Next() *ProxyTarget
}
)
func proxyHTTP(t *ProxyTarget) http.Handler {
return httputil.NewSingleHostReverseProxy(t.URL)
}
func proxyRaw(t *ProxyTarget, c echo.Context) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
h, ok := w.(http.Hijacker)
if !ok {
c.Error(errors.New("proxy raw, not a hijacker"))
return
}
in, _, err := h.Hijack()
if err != nil {
c.Error(fmt.Errorf("proxy raw, hijack error=%v, url=%s", r.URL, err))
return
}
defer in.Close()
out, err := net.Dial("tcp", t.URL.Host)
if err != nil {
he := echo.NewHTTPError(http.StatusBadGateway, fmt.Sprintf("proxy raw, dial error=%v, url=%s", r.URL, err))
c.Error(he)
return
}
defer out.Close()
err = r.Write(out)
if err != nil {
he := echo.NewHTTPError(http.StatusBadGateway, fmt.Sprintf("proxy raw, request copy error=%v, url=%s", r.URL, err))
c.Error(he)
return
}
errc := make(chan error, 2)
cp := func(dst io.Writer, src io.Reader) {
_, err := io.Copy(dst, src)
errc <- err
}
go cp(out, in)
go cp(in, out)
err = <-errc
if err != nil && err != io.EOF {
c.Logger().Errorf("proxy raw, error=%v, url=%s", r.URL, err)
}
})
}
// Next randomly returns an upstream target.
func (r *RandomBalancer) Next() *ProxyTarget {
if r.random == nil {
r.random = rand.New(rand.NewSource(int64(time.Now().Nanosecond())))
}
return r.Targets[r.random.Intn(len(r.Targets))]
}
// Next returns an upstream target using round-robin technique.
func (r *RoundRobinBalancer) Next() *ProxyTarget {
r.i = r.i % uint32(len(r.Targets))
t := r.Targets[r.i]
atomic.AddUint32(&r.i, 1)
return t
}
// Proxy returns an HTTP/WebSocket reverse proxy middleware.
func Proxy(config ProxyConfig) echo.MiddlewareFunc {
// Defaults
if config.Skipper == nil {
config.Skipper = DefaultLoggerConfig.Skipper
}
if config.Balancer == nil {
panic("echo: proxy middleware requires balancer")
}
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) (err error) {
req := c.Request()
res := c.Response()
tgt := config.Balancer.Next()
// Fix header
if req.Header.Get(echo.HeaderXRealIP) == "" {
req.Header.Set(echo.HeaderXRealIP, c.RealIP())
}
if req.Header.Get(echo.HeaderXForwardedProto) == "" {
req.Header.Set(echo.HeaderXForwardedProto, c.Scheme())
}
if c.IsWebSocket() && req.Header.Get(echo.HeaderXForwardedFor) == "" { // For HTTP, it is automatically set by Go HTTP reverse proxy.
req.Header.Set(echo.HeaderXForwardedFor, c.RealIP())
}
// Proxy
switch {
case c.IsWebSocket():
proxyRaw(tgt, c).ServeHTTP(res, req)
case req.Header.Get(echo.HeaderAccept) == "text/event-stream":
default:
proxyHTTP(tgt).ServeHTTP(res, req)
}
return
}
}
}
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