middleware.go

package main

import (
	"github.com/AsynkronIT/protoactor-go/actor"
	"log"
	"os"
	"os/signal"
	"syscall"
	"time"
)

func newInboundMiddleware() actor.InboundMiddleware {
	cnt := 0
	return func(next actor.ActorFunc) actor.ActorFunc {
		return func(ctx actor.Context) {
			cnt++
			log.Printf("Start handling incoming message #%d: %#v", cnt, ctx.Message())
			next(ctx)
			log.Printf("End handling incoming message #%d: %#v", cnt, ctx.Message())
		}
	}
}

func newOutboundMiddleware() actor.OutboundMiddleware {
	cnt := 0
	return func(next actor.SenderFunc) actor.SenderFunc {
		return func(ctx actor.Context, target *actor.PID, envelope *actor.MessageEnvelope) {
			cnt++
			log.Printf("Start sending message #%d to %s", cnt, target.Id)
			next(ctx, target, envelope)
			log.Printf("End sending message #%d to %s", cnt, target.Id)
		}
	}
}

type ping struct{}

type pong struct{}

func main() {
	pongProps := actor.
		FromFunc(func(ctx actor.Context) {
			switch ctx.Message().(type) {
			case *ping:
				ctx.Respond(&pong{})
			}
		})
	pongPid, _ := actor.SpawnNamed(pongProps, "pong")

	// Output should be somewhat like below.
	// Because ping actor receives both signal of struct{}{} and a pong message of &pong{},
	// the printed number of execution is doubled comparing to that of pong actor.
	//
	// 2018/11/24 12:59:25 Start handling incoming message #1: &actor.Started{}
	// 2018/11/24 12:59:25 End handling incoming message #1: &actor.Started{}
	// 2018/11/24 12:59:26 Start handling incoming message #2: struct {}{}
	// 2018/11/24 12:59:26 Received signal
	// 2018/11/24 12:59:26 Start sending message #1 to pong
	// 2018/11/24 12:59:26 End sending message #1 to pong
	// 2018/11/24 12:59:26 End handling incoming message #2: struct {}{}
	// 2018/11/24 12:59:26 Start handling incoming message #3: &main.pong{}
	// 2018/11/24 12:59:26 Received pong
	// 2018/11/24 12:59:26 End handling incoming message #3: &main.pong{}
	// 2018/11/24 12:59:27 Start handling incoming message #4: struct {}{}
	// 2018/11/24 12:59:27 Received signal
	// 2018/11/24 12:59:27 Start sending message #2 to pong
	// 2018/11/24 12:59:27 End sending message #2 to pong
	// 2018/11/24 12:59:27 End handling incoming message #4: struct {}{}
	// 2018/11/24 12:59:27 Start handling incoming message #5: &main.pong{}
	// 2018/11/24 12:59:27 Received pong
	// 2018/11/24 12:59:27 End handling incoming message #5: &main.pong{}
	// 2018/11/24 12:59:28 Start handling incoming message #6: struct {}{}
	// 2018/11/24 12:59:28 Received signal
	// 2018/11/24 12:59:28 Start sending message #3 to pong
	// 2018/11/24 12:59:28 End sending message #3 to pong
	// 2018/11/24 12:59:28 End handling incoming message #6: struct {}{}
	// 2018/11/24 12:59:28 Start handling incoming message #7: &main.pong{}
	// 2018/11/24 12:59:28 Received pong
	// 2018/11/24 12:59:28 End handling incoming message #7: &main.pong{}
	// ^C2018/11/24 12:59:29 Finish
	pingProps := actor.
		FromFunc(func(ctx actor.Context) {
			switch ctx.Message().(type) {
			case struct{}:
				log.Print("Received signal")
				ctx.Request(pongPid, &ping{})

			case *pong:
				log.Print("Received pong")

			}
		}).
		WithMiddleware(newInboundMiddleware()).
		WithOutboundMiddleware(newOutboundMiddleware())
	pingPid, _ := actor.SpawnNamed(pingProps, "ping")

	finish := make(chan os.Signal, 1)
	signal.Notify(finish, os.Interrupt)
	signal.Notify(finish, syscall.SIGTERM)

	ticker := time.NewTicker(1 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			pingPid.Tell(struct{}{})

		case <-finish:
			pingPid.Stop()
			pongPid.Stop()
			log.Print("Finish")
			return

		}
	}
}

Hi, this example doesn't work with current version of protoactor, I corrected it a little bit in my fork https://gist.github.com/rocc0/49e8623ff83859cf5028f6ecd5fbfe73

Thanks for the fix, @rocc0.
As described in the very first article of my blog entries, it used the latest version possible at the moment: asynkron/protoactor-go@3992780.
Lately, I've added go.mod/go.sum for example repositories for version management.
I'll do something to these gist code fragments and blog entries to keep updated.