/
revproxy.go
173 lines (159 loc) · 3.86 KB
/
revproxy.go
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package main
import (
"encoding/json"
"errors"
"flag"
"log"
"net"
"net/http"
"net/http/httputil"
_ "net/http/pprof"
"net/url"
"os"
"strings"
"time"
"golang.org/x/net/netutil"
)
func main() {
params := struct {
Addr string
Conf string
Prof string
MaxConn int
}{
Addr: "0.0.0.0:8080",
Conf: "/etc/revproxy.json",
MaxConn: 1000,
}
flag.StringVar(¶ms.Addr, "addr", params.Addr, "`address` to listen at")
flag.StringVar(¶ms.Conf, "conf", params.Conf, "configuration `file` with mapping")
flag.StringVar(¶ms.Prof, "prof", params.Prof, "`address` to expose profile data at")
flag.IntVar(¶ms.MaxConn, "maxconn", params.MaxConn, "maximum number of connections to accept")
flag.Parse()
conf, err := readConfig(params.Conf)
if err != nil {
log.Fatal(err)
}
proxy, err := NewRevProxy(conf)
if err != nil {
log.Fatal(err)
}
ln, err := Listen(params.Addr, params.MaxConn)
if err != nil {
log.Fatal(err)
}
srv := &http.Server{
Handler: proxy,
ReadTimeout: 65 * time.Second,
WriteTimeout: 65 * time.Second,
}
if params.Prof != "" {
go func() {
log.Println(http.ListenAndServe(params.Prof, nil))
}()
}
log.Fatal(srv.Serve(ln))
}
func Listen(addr string, maxconn int) (net.Listener, error) {
if maxconn < 1 {
return nil, errors.New("maxconn should be positive")
}
ln, err := net.Listen("tcp", addr)
if err != nil {
return nil, err
}
return netutil.LimitListener(ln, maxconn), nil
}
type RevProxy struct {
backends map[string]*httputil.ReverseProxy
buckets map[string]chan struct{}
}
func NewRevProxy(conf Config) (*RevProxy, error) {
if err := conf.validate(); err != nil {
return nil, err
}
rp := &RevProxy{
backends: make(map[string]*httputil.ReverseProxy),
buckets: make(map[string]chan struct{}),
}
transport := http.DefaultTransport
transport.(*http.Transport).MaxIdleConnsPerHost = conf.MaxKeepalivesPerBackend
for k, v := range conf.Mapping {
if strings.HasPrefix(v, "/") {
// destination is unix socket. Make a custom transport
// which routes any requests into this socket via
// custom dialer, construct fake destination url from
// source domain itself
dst, err := url.Parse("http://" + k)
if err != nil {
return nil, err
}
rp.buckets[k] = make(chan struct{}, conf.MaxConnsPerBackend)
p := httputil.NewSingleHostReverseProxy(dst)
v := v // shadow variable
p.Transport = &http.Transport{
Dial: func(network, addr string) (net.Conn, error) {
return net.Dial("unix", v)
},
}
rp.backends[k] = p
continue
}
// treat destination as tcp
dst, err := url.Parse(v)
if err != nil {
return nil, err
}
rp.buckets[k] = make(chan struct{}, conf.MaxConnsPerBackend)
p := httputil.NewSingleHostReverseProxy(dst)
p.Transport = transport
rp.backends[k] = p
}
return rp, nil
}
func readConfig(name string) (Config, error) {
f, err := os.Open(name)
if err != nil {
return Config{}, err
}
defer f.Close()
var conf Config
dec := json.NewDecoder(f)
if err := dec.Decode(&conf); err != nil {
return Config{}, err
}
return conf, nil
}
type Config struct {
MaxConnsPerBackend int
MaxKeepalivesPerBackend int
Mapping map[string]string
}
func (c Config) validate() error {
if c.MaxConnsPerBackend < 1 {
return errors.New("MaxConnsPerBackend is too low")
}
if c.MaxKeepalivesPerBackend < 1 {
return errors.New("MaxKeepalivesPerBackend is too low")
}
if len(c.Mapping) == 0 {
return errors.New("no backends provided")
}
return nil
}
func (rp *RevProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
p, ok := rp.backends[r.Host]
if !ok {
http.Error(w, "Bad Gateway", http.StatusBadGateway)
return
}
bkt := rp.buckets[r.Host]
select {
case bkt <- struct{}{}:
defer func() { <-bkt }()
p.ServeHTTP(w, r)
default:
http.Error(w, "Service Unavailable", http.StatusServiceUnavailable)
return
}
}