// Spawn starts a new Engine in a child process and returns
// a proxy Engine through which it can be controlled.
//
// The commands available on the child engine are determined
// by an earlier call to Init. It is important that Init be
// called at the very beginning of the current program - this
// allows it to be called as a re-execution hook in the child
// process.
//
// Long story short, if you want to expose `myservice` in a child
// process, do this:
//
// func main() {
// spawn.Init(myservice)
// [..]
// child, err := spawn.Spawn()
// [..]
// child.Job("dosomething").Run()
// }
func Spawn() (*engine.Engine, error) {
if !initCalled {
return nil, fmt.Errorf("spawn.Init must be called at the top of the main() function")
}
cmd := exec.Command(utils.SelfPath())
cmd.Env = append(cmd.Env, "ENGINESPAWN=1")
local, remote, err := beam.SocketPair()
if err != nil {
return nil, err
}
child, err := beam.FileConn(local)
if err != nil {
local.Close()
remote.Close()
return nil, err
}
local.Close()
cmd.ExtraFiles = append(cmd.ExtraFiles, remote)
// FIXME: the beam/engine glue has no way to inform the caller
// of the child's termination. The next call will simply return
// an error.
if err := cmd.Start(); err != nil {
child.Close()
return nil, err
}
eng := engine.New()
if err := engine.NewSender(child).Install(eng); err != nil {
child.Close()
return nil, err
}
return eng, nil
}
func CmdExec(args []string, stdout, stderr io.Writer, in beam.Receiver, out beam.Sender) {
cmd := exec.Command(args[1], args[2:]...)
cmd.Stdout = stdout
cmd.Stderr = stderr
//cmd.Stdin = os.Stdin
local, remote, err := beam.SocketPair()
if err != nil {
fmt.Fprintf(stderr, "%v\n", err)
return
}
child, err := beam.FileConn(local)
if err != nil {
local.Close()
remote.Close()
fmt.Fprintf(stderr, "%v\n", err)
return
}
local.Close()
cmd.ExtraFiles = append(cmd.ExtraFiles, remote)
var tasks sync.WaitGroup
tasks.Add(1)
go func() {
defer Debugf("done copying to child\n")
defer tasks.Done()
defer child.CloseWrite()
beam.Copy(child, in)
}()
tasks.Add(1)
go func() {
defer Debugf("done copying from child %d\n")
defer tasks.Done()
r := beam.NewRouter(out)
r.NewRoute().All().Handler(func(p []byte, a *os.File) error {
return out.Send(data.Message(p).Set("pid", fmt.Sprintf("%d", cmd.Process.Pid)).Bytes(), a)
})
beam.Copy(r, child)
}()
execErr := cmd.Run()
// We can close both ends of the socket without worrying about data stuck in the buffer,
// because unix socket writes are fully synchronous.
child.Close()
tasks.Wait()
var status string
if execErr != nil {
status = execErr.Error()
} else {
status = "ok"
}
out.Send(data.Empty().Set("status", status).Set("cmd", args...).Bytes(), nil)
}
func ReceiveFromConn(connections chan net.Conn, dst beam.Sender) error {
for conn := range connections {
err := func() error {
Logf("parsing message from network...\n")
defer Logf("done parsing message from network\n")
buf := make([]byte, 4098)
n, err := conn.Read(buf)
if n == 0 {
conn.Close()
if err == io.EOF {
return nil
} else {
return err
}
}
Logf("decoding message from '%s'\n", buf[:n])
header, skip, err := data.DecodeString(string(buf[:n]))
if err != nil {
conn.Close()
return err
}
pub, priv, err := beam.SocketPair()
if err != nil {
return err
}
Logf("decoded message: %s\n", data.Message(header).Pretty())
go func(skipped []byte, conn net.Conn, f *os.File) {
// this closes both conn and f
if len(skipped) > 0 {
if _, err := f.Write(skipped); err != nil {
Logf("ERROR: %v\n", err)
f.Close()
conn.Close()
return
}
}
bicopy(conn, f)
}(buf[skip:n], conn, pub)
if err := dst.Send([]byte(header), priv); err != nil {
return err
}
return nil
}()
if err != nil {
Logf("Error reading from connection: %v\n", err)
}
}
return nil
}