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proxy.go
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proxy.go
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// MIT License
// Copyright (c) 2020 Tree Xie
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package middleware
import (
"errors"
"net/http"
"net/http/httputil"
"net/url"
"regexp"
"strconv"
"strings"
"sync"
"github.com/vicanso/elton"
"github.com/vicanso/hes"
)
const (
// ErrProxyCategory proxy error category
ErrProxyCategory = "elton-proxy"
ProxyTargetKey = "proxyTarget"
)
var (
// ErrProxyTargetIsNil target is nil
ErrProxyTargetIsNil = &hes.Error{
Exception: true,
Message: "target can not be nil",
StatusCode: http.StatusBadRequest,
Category: ErrProxyCategory,
}
ErrProxyNoTargetFunction = errors.New("require target or targer picker")
)
type (
// ProxyDone http proxy done callback
ProxyDone func(*elton.Context)
// ProxyTargetPicker target picker function
ProxyTargetPicker func(c *elton.Context) (*url.URL, ProxyDone, error)
// Config proxy config
ProxyConfig struct {
// Done proxy done callback
Done ProxyDone
Target *url.URL
Rewrites []string
Host string
Transport http.RoundTripper
TargetPicker ProxyTargetPicker
Skipper elton.Skipper
}
rewriteRegexp struct {
Regexp *regexp.Regexp
Value string
}
)
// bufferPool buffer pool for proxy read response content
type bufferPool struct {
pool sync.Pool
}
func newBufferPool(size int) *bufferPool {
p := &bufferPool{}
p.pool.New = func() interface{} {
buf := make([]byte, size)
return &buf
}
return p
}
func (bp *bufferPool) Get() []byte {
p := bp.pool.Get().(*[]byte)
return *p
}
func (bp *bufferPool) Put(data []byte) {
bp.pool.Put(&data)
}
func captureTokens(pattern *regexp.Regexp, input string) *strings.Replacer {
groups := pattern.FindAllStringSubmatch(input, -1)
if groups == nil {
return nil
}
values := groups[0][1:]
replace := make([]string, 2*len(values))
for i, v := range values {
j := 2 * i
replace[j] = "$" + strconv.Itoa(i+1)
replace[j+1] = v
}
return strings.NewReplacer(replace...)
}
func urlRewrite(rewrites []*rewriteRegexp, req *http.Request) {
for _, rewrite := range rewrites {
replacer := captureTokens(rewrite.Regexp, req.URL.Path)
if replacer != nil {
req.URL.Path = replacer.Replace(rewrite.Value)
}
}
}
// generateRewrites generate rewrites
func generateRewrites(arr []string) (rewrites []*rewriteRegexp, err error) {
size := len(arr)
if size == 0 {
return
}
rewrites = make([]*rewriteRegexp, 0, size)
for _, value := range arr {
arr := strings.Split(value, ":")
if len(arr) != 2 {
continue
}
k := arr[0]
v := arr[1]
k = strings.Replace(k, "*", "(\\S*)", -1)
reg, e := regexp.Compile(k)
if e != nil {
err = e
return
}
rewrites = append(rewrites, &rewriteRegexp{
Regexp: reg,
Value: v,
})
}
return
}
// NewProxy returns a new proxy middleware, it can proxy the request to other server.
// It will throw a panic if Target and TargetPicker function is nil.
// It will throw a panic if Rewrites config is not a regexp.
func NewProxy(config ProxyConfig) elton.Handler {
if config.Target == nil && config.TargetPicker == nil {
panic(ErrProxyNoTargetFunction)
}
rewrites, err := generateRewrites(config.Rewrites)
if err != nil {
panic(err)
}
skipper := config.Skipper
if skipper == nil {
skipper = elton.DefaultSkipper
}
// 默认使用32KB的buffer
bufPool := newBufferPool(32 * 1024)
return func(c *elton.Context) error {
if skipper(c) {
return c.Next()
}
if config.Done != nil {
defer config.Done(c)
}
target := config.Target
var done ProxyDone
if target == nil {
target, done, err = config.TargetPicker(c)
if err != nil {
return err
}
if done != nil {
defer done(c)
}
}
// 如果无target,则抛错
if target == nil {
return ErrProxyTargetIsNil
}
c.Set(ProxyTargetKey, target.String())
p := httputil.NewSingleHostReverseProxy(target)
if config.Transport != nil {
p.Transport = config.Transport
}
p.BufferPool = bufPool
req := c.Request
var originalPath, originalHost string
if len(rewrites) != 0 {
originalPath = req.URL.Path
urlRewrite(rewrites, req)
}
if config.Host != "" {
originalHost = req.Host
req.Host = config.Host
}
p.ErrorHandler = func(_ http.ResponseWriter, _ *http.Request, e error) {
he := hes.NewWithError(e)
he.Category = ErrProxyCategory
he.Exception = true
err = he
}
p.ServeHTTP(c, req)
if err != nil {
return err
}
if originalPath != "" {
req.URL.Path = originalPath
}
if originalHost != "" {
req.Host = originalHost
}
return c.Next()
}
}