git/git

// 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)
    }
}