mirror of
https://github.com/astaxie/beego.git
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159 lines
3.1 KiB
Go
159 lines
3.1 KiB
Go
// Zero-downtime restarts in Go.
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package beego
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import (
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"errors"
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"fmt"
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"log"
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"net"
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"os"
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"os/exec"
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"os/signal"
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"reflect"
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"strconv"
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"sync"
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"syscall"
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)
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const (
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FDKey = "BEEGO_HOT_FD"
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)
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// Export an error equivalent to net.errClosing for use with Accept during
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// a graceful exit.
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var ErrClosing = errors.New("use of closed network connection")
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var ErrInitStart = errors.New("init from")
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// Allows for us to notice when the connection is closed.
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type conn struct {
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net.Conn
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wg *sync.WaitGroup
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isclose bool
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lock sync.Mutex
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}
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func (c conn) Close() error {
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c.lock.Lock()
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defer c.lock.Unlock()
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err := c.Conn.Close()
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if !c.isclose && err == nil {
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c.wg.Done()
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c.isclose = true
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}
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return err
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}
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type stoppableListener struct {
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net.Listener
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count int64
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stopped bool
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wg sync.WaitGroup
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}
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var theStoppable *stoppableListener
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func newStoppable(l net.Listener) (sl *stoppableListener) {
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sl = &stoppableListener{Listener: l}
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// this goroutine monitors the channel. Can't do this in
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// Accept (below) because once it enters sl.Listener.Accept()
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// it blocks. We unblock it by closing the fd it is trying to
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// accept(2) on.
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go func() {
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WaitSignal(l)
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sl.stopped = true
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sl.Listener.Close()
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}()
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return
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}
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func (sl *stoppableListener) Accept() (c net.Conn, err error) {
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c, err = sl.Listener.Accept()
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if err != nil {
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return
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}
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sl.wg.Add(1)
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// Wrap the returned connection, so that we can observe when
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// it is closed.
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c = conn{Conn: c, wg: &sl.wg}
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return
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}
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func WaitSignal(l net.Listener) error {
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ch := make(chan os.Signal, 1)
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signal.Notify(ch, syscall.SIGTERM, syscall.SIGHUP)
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for {
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sig := <-ch
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log.Println(sig.String())
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switch sig {
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case syscall.SIGTERM:
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return nil
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case syscall.SIGHUP:
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err := Restart(l)
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if nil != err {
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return err
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}
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return nil
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}
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}
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return nil // It'll never get here.
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}
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func CloseSelf() error {
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ppid := os.Getpid()
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if ppid == 1 { // init provided sockets, for example systemd
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return nil
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}
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p, err := os.FindProcess(ppid)
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if err != nil {
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return err
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}
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return p.Kill()
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}
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// Re-exec this image without dropping the listener passed to this function.
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func Restart(l net.Listener) error {
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argv0, err := exec.LookPath(os.Args[0])
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if nil != err {
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return err
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}
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wd, err := os.Getwd()
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if nil != err {
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return err
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}
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v := reflect.ValueOf(l).Elem().FieldByName("fd").Elem()
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fd := uintptr(v.FieldByName("sysfd").Int())
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allFiles := append([]*os.File{os.Stdin, os.Stdout, os.Stderr},
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os.NewFile(fd, string(v.FieldByName("sysfile").String())))
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p, err := os.StartProcess(argv0, os.Args, &os.ProcAttr{
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Dir: wd,
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Env: append(os.Environ(), fmt.Sprintf("%s=%d", FDKey, fd)),
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Files: allFiles,
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})
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if nil != err {
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return err
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}
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log.Printf("spawned child %d\n", p.Pid)
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return nil
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}
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func GetInitListner(tcpaddr *net.TCPAddr) (l net.Listener, err error) {
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countStr := os.Getenv(FDKey)
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if countStr == "" {
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return net.ListenTCP("tcp", tcpaddr)
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}
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count, err := strconv.Atoi(countStr)
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if err != nil {
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return nil, err
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}
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f := os.NewFile(uintptr(count), "listen socket")
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l, err = net.FileListener(f)
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if err != nil {
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return nil, err
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}
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return l, nil
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}
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