proxy.go

[bnhassin]

os.exec.Command

// Copyright 2012 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
"fmt"
"log"
"net"
"net/http"
"net/http/httputil"
"os"
"os/exec"
"os/signal"
"sync"
"syscall"
"time"
)

type Proxy struct {
BuildLabel string
MaxIdleDuration time.Duration
PollUpdateInterval time.Duration

    ul        net.Listener
    httpAddr  string
    httpsAddr string

}

func (p *Proxy) Run() error {
hl, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
return fmt.Errorf("http listen failed: %v", err)
}
defer hl.Close()

    hsl, err := net.Listen("tcp", "127.0.0.1:0")
    if err != nil {
            return fmt.Errorf("https listen failed: %v", err)
    }
    defer hsl.Close()

    p.ul, err = DefaultSocket.Listen()
    if err != nil {
            c, derr := DefaultSocket.Dial()
            if derr == nil {
                    c.Close()
                    fmt.Println("OK\nA proxy is already running... exiting")
                    return nil
            } else if e, ok := derr.(*net.OpError); ok && e.Err == syscall.ECONNREFUSED {
                    // Nothing is listening on the socket, unlink it and try again.
                    syscall.Unlink(DefaultSocket.Path())
                    p.ul, err = DefaultSocket.Listen()
            }
            if err != nil {
                    return fmt.Errorf("unix listen failed on %v: %v", DefaultSocket.Path(), err)
            }
    }
    defer p.ul.Close()
    go p.closeOnSignal()
    go p.closeOnUpdate()

    p.httpAddr = hl.Addr().String()
    p.httpsAddr = hsl.Addr().String()
    fmt.Printf("OK\nListening on unix socket=%v http=%v https=%v\n",
            p.ul.Addr(), p.httpAddr, p.httpsAddr)

    result := make(chan error, 2)
    go p.serveUnix(result)
    go func() {
            result <- http.Serve(hl, &httputil.ReverseProxy{
                    FlushInterval: 500 * time.Millisecond,
                    Director:      func(r *http.Request) {},
            })
    }()
    go func() {
            result <- http.Serve(hsl, &httputil.ReverseProxy{
                    FlushInterval: 500 * time.Millisecond,
                    Director: func(r *http.Request) {
                            r.URL.Scheme = "https"
                    },
            })
    }()
    return <-result

}

type socketContext struct {
sync.WaitGroup
mutex sync.Mutex
last time.Time
}

func (sc *socketContext) Done() {
sc.mutex.Lock()
defer sc.mutex.Unlock()
sc.last = time.Now()
sc.WaitGroup.Done()
}

func (p *Proxy) serveUnix(result chan<- error) {
sockCtx := &socketContext{}
go p.closeOnIdle(sockCtx)

    var err error
    for {
            var uconn net.Conn
            uconn, err = p.ul.Accept()
            if err != nil {
                    err = fmt.Errorf("accept failed: %v", err)
                    break
            }
            sockCtx.Add(1)
            go p.handleUnixConn(sockCtx, uconn)
    }
    sockCtx.Wait()
    result <- err

}

func (p *Proxy) handleUnixConn(sockCtx *socketContext, uconn net.Conn) {
defer sockCtx.Done()
defer uconn.Close()
data := []byte(fmt.Sprintf("%v\n%v", p.httpsAddr, p.httpAddr))
uconn.SetDeadline(time.Now().Add(5 * time.Second))
for i := 0; i < 2; i++ {
if n, err := uconn.Write(data); err != nil {
log.Printf("error sending http addresses: %+v\n", err)
return
} else if n != len(data) {
log.Printf("sent %d data bytes, wanted %d\n", n, len(data))
return
}
if _, err := uconn.Read([]byte{0, 0, 0, 0}); err != nil {
log.Printf("error waiting for Ack: %+v\n", err)
return
}
}
// Wait without a deadline for the client to finish via EOF
uconn.SetDeadline(time.Time{})
uconn.Read([]byte{0, 0, 0, 0})
}

func (p *Proxy) closeOnIdle(sockCtx *socketContext) {
for d := p.MaxIdleDuration; d > 0; {
time.Sleep(d)
sockCtx.Wait()
sockCtx.mutex.Lock()
if d = sockCtx.last.Add(p.MaxIdleDuration).Sub(time.Now()); d <= 0 {
log.Println("graceful shutdown from idle timeout")
p.ul.Close()
}
sockCtx.mutex.Unlock()
}
}

func (p *Proxy) closeOnUpdate() {
for {
time.Sleep(p.PollUpdateInterval)
if out, err := exec.Command(os.Args[0], "--print_label").Output(); err != nil {
log.Printf("error polling for updated binary: %v\n", err)
} else if s := string(out[:len(out)-1]); p.BuildLabel != s {
log.Printf("graceful shutdown from updated binary: %q --> %q\n", p.BuildLabel, s)
p.ul.Close()
break
}
}
}

func (p *Proxy) closeOnSignal() {
ch := make(chan os.Signal, 10)
signal.Notify(ch, os.Interrupt, os.Kill, os.Signal(syscall.SIGTERM), os.Signal(syscall.SIGHUP))
sig := <-ch
p.ul.Close()
switch sig {
case os.Signal(syscall.SIGHUP):
log.Printf("graceful shutdown from signal: %v\n", sig)
default:
log.Fatalf("exiting from signal: %v\n", sig)
}
}