func main() {
eng := engine.New()
c, err := net.Dial("unix", "beam.sock")
if err != nil {
fmt.Fprintf(os.Stderr, "%v\n", err)
return
}
defer c.Close()
f, err := c.(*net.UnixConn).File()
if err != nil {
fmt.Fprintf(os.Stderr, "%v\n", err)
return
}
child, err := beam.FileConn(f)
if err != nil {
fmt.Fprintf(os.Stderr, "%v\n", err)
return
}
defer child.Close()
sender := engine.NewSender(child)
sender.Install(eng)
cmd := eng.Job(os.Args[1], os.Args[2:]...)
cmd.Stdout.Add(os.Stdout)
cmd.Stderr.Add(os.Stderr)
if err := cmd.Run(); err != nil {
fmt.Fprintf(os.Stderr, "%v\n", err)
os.Exit(1)
}
}
// 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
}