Poison (#46)

* poison returns a wait group api

* clean API

* updated README

README.md

@@ -17,7 +17,6 @@ By using the Actor Model in your application, you can build highly scalable and
 
 ## Features
 
-- lock free LMAX based message queue for ultra low latency messaging
 - guaranteed message delivery on receiver failure (buffer mechanism)
 - fire&forget or request&response messaging, or both.
 - dRPC as the transport layer
@@ -71,7 +70,9 @@ func main() {
 	engine := actor.NewEngine()
 	pid := engine.Spawn(newFoo, "foo")
 	engine.Send(pid, &message{data: "hello world!"})
-	time.Sleep(time.Second * 1)
+
+	// Stop the actor, but let it process its messages first.
+	engine.Poison(pid).Wait()
 }
 ```
 

actor/engine.go

@@ -187,16 +187,19 @@ func (e *Engine) SendRepeat(pid *PID, msg any, interval time.Duration) SendRepea
 // Poison will send a poisonPill to the process that is associated with the given PID.
 // The process will shut down once it processed all its messages before the poisonPill
 // was received. If given a WaitGroup, you can wait till the process is completely shutdown.
-func (e *Engine) Poison(pid *PID, wg ...*sync.WaitGroup) {
+func (e *Engine) Poison(pid *PID, wg ...*sync.WaitGroup) *sync.WaitGroup {
 	var _wg *sync.WaitGroup
 	if len(wg) > 0 {
 		_wg = wg[0]
-		_wg.Add(1)
+	} else {
+		_wg = &sync.WaitGroup{}
 	}
+	_wg.Add(1)
 	proc := e.Registry.get(pid)
 	if proc != nil {
 		e.SendLocal(pid, poisonPill{_wg}, nil)
 	}
+	return _wg
 }
 
 func (e *Engine) SendLocal(pid *PID, msg any, sender *PID) {

examples/helloworld/main.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"fmt"
-	"sync"
 
 	"github.com/anthdm/hollywood/actor"
 )
@@ -34,7 +33,5 @@ func main() {
 	for i := 0; i < 100; i++ {
 		engine.Send(pid, &message{data: "hello world!"})
 	}
-	wg := sync.WaitGroup{}
-	engine.Poison(pid, &wg)
-	wg.Wait()
+	engine.Poison(pid).Wait()
 }