Last year this session’s speaker and his colleagues started a new Internet of Things project: Internet of (Lego) Trains. They wanted to figure out if they could use Java or Scala/Akka on IoT hardware. The Lego trains are equipped with a Raspberry Pi, camera, wireless dongle, infrared transmitter, speaker, RFID reader, and battery pack. Next to that are automated switch tracks and cameras, again with the help of Raspberry Pi’s. To control the trains and other parts, they built an actor-based application with Scala, Akka, Akka HTTP, and AngularJS. The session covers when and how to use Akka HTTP and remote actors to create a new generation of applications. It also presents the results of the performance tests they did to compare the two options. A live demo is of course included.

1. USING ACTORS FOR THE
INTERNET OF (LEGO) TRAINS
Johan Janssen, Info Support @johanjanssen42

2. Disclaimer:
No Lego was harmed beyond
repair during the project.

3. CONTENT
 Why?
 Getting started
 Architecture
 Actors
 Remote actors
 Shared protocol
 HTTP vs Actors
 Conclusion
 Challenges
 Questions

4. WHY?

5. Why?

7. GETTING STARTED

8. MINIMAL INGREDIENTS FOR 1TRAIN
ABOUT € 50
Raspberry Pi A+ / Raspberry Pi Zero
Wifi dongle
EDUP Ultra-Mini Nano USB 2.0 802.11n
USB battery pack
Anker® 2. Gen Astro Mini 3200mAh
Infrared transmitter
Keyes 38KHz IR InfraredTransmitter Module for
Arduino

10. COMPARISON
Idle (mA) Memory (MB) CPU (Mhz) Size (mm)
RPi A+ 100 256 700 65 *56
RPi Zero 100 512 1000 65 * 30
RPi B+ 200 512 700 85 *56
RPi 2 B 230 1024 4*900 85 *56
Odroid C1 325 1024 4*1500 85 *56
Particle
Photon
80-100 128KB 120 38 * 21

11. ARCHITECTURE

12. Architecture

13. LTCC
(Angular)
LTCC
(Java)
DeviceControl
(Java)
Infrared
(C and LIRC)
RFID
(C)
SwitchControl
(Java)
Servo
(Python)
RPi-Cam-Web-
Interface
(C)

14. LTCC
(Angular)
LTCC
(Scala/Akka)
DeviceControl
(Scala/Akka)
Infrared
(C and LIRC)
RFID
(C)
SwitchControl
(Scala/Akka)
Servo
(Python)
Leds with Photon
(C)
RPi-Cam-Web-
Interface
(C)

15. LTCC (Laptop / Pi)
LegoTrain
SwitchControl (Pi) Camera (Pi)
Device
Control
(Pi)

16. Original
controls

17. Infrared

18. Sound

20. Camera

22. Switches

26. LTCC APPLICATION

27. ACTORS

28. AKKA ACTORS
class Worker extends Actor {
def receive = {
case x =>
println(x)
}
}
val system = ActorSystem("ExampleActorSystem")
val workerActorRef = system.actorOf(Props[Worker])
workerActorRef ! "Hello conference"

29. REMOTE ACTORS

31. AKKA REMOTE ACTOR CALL
val workerActorRef =
system.actorOf(Props[Worker])
val workerActorRef =
system.actorSelection("akka.tcp://
ExampleActorSystem@127.0.0.1:9005
/user/workerActor")

32. AKKA REMOTE ACTOR CONFIGURATION
akka {
actor {
provider = "akka.remote.RemoteActorRefProvider"
}
remote {
enabled-transports = ["akka.remote.netty.tcp"]
netty.tcp {
hostname = "127.0.0.1"
port = 9002
}
}
}

33. SHARED PROTOCOL

34. Actor on
JVM 1
Actor on
JVM 2
Messages

35. Actor on
laptop
Musicservice
Actor on
Raspberry PiPlay
message
CONCRETE EXAMPLE

36. Server
application
MessageProtocol
Raspberry Pi
application

37. EXAMPLE MESSAGE
object MusicServiceMessage {
case class Play(filename: String)
case class MusicList(filenames: List[Song])
}

38. MESSAGE USED BY APPLICATION
val actorRef = context.actorSelection(
"akka.tcp://[Actorsystem]@
[IP]:[port]/user/musicservice")
actorRef !
[packagename].MusicServiceMessage.Play(filename)

39. HTTP VS REMOTE ACTOR

40. ADVANTAGES REMOTE ACTORS
 No converting to JSON/SOAP
 More natural programming
 Concurrent on default
 Built-in load balancer
 Built-in circuit breaker

41. ADVANTAGES HTTP
 Indepedent of technology
 Loosely coupled

42. FAT JAR (SBT ASSEMBLY) IN MB
0
5
10
15
20
25
Local actor Remote actor Akka HTTP Spring boot

43. GATLING

44. class ExampleSimulation extends Simulation {
val scn = scenario("My scenario").repeat(100) {
exec(
http("Ping")
.get("http://localhost:8080/ping")
.check(status.is(200))
).pause(100 millisecond) // Optional
}
setUp(scn.inject(
rampUsers(1000) over (10 seconds) // Changing
))
}

45. PERFORMANCETEST SETUP
JVM 1
Akka HTTP
HTTP: /ping
pong JVM 2
Akka HTTP
HTTP: /pong
pong
JVM 1
Akka HTTP
HTTP: /ping
pong JVM 2
Akka remote actor
Akka over TCP: pong
pong

46. 0
20
40
60
80
100
120
50 50 no pause 500 500 no pause 1000 1000 no pause
Mean response time (ms)
Akka HTTP Remote actor

47. 0
100
200
300
400
500
600
700
800
900
50 50 no pause 500 500 no pause 1000 1000 no pause
Max response time (ms)
Akka HTTP Remote actor

48. 0
50
100
150
200
250
300
350
50 50 no pause 500 500 no pause 1000 1000 no pause
99 percentile (ms)
Akka HTTP Remote actor

49. GRADUATION STUDENT
REST could handle around 600 users
Remote actors probably around 3300 users

50. REST is dead,
long live remote actors!
- Johan Janssen

52. 0
5
10
15
20
25
30
50 50 no pause 500 500 no pause 1000 1000 no pause
Mean response time (ms)
Remote actor Spring boot

53. 0
100
200
300
400
500
600
700
800
900
50 50 no pause 500 500 no pause 1000 1000 no pause
Max response time (ms)
Remote actor Spring boot

54. 0
20
40
60
80
100
120
140
160
50 50 no pause 500 500 no pause 1000 1000 no pause
99 percentile (ms)
Remote actor Spring boot

55. Challenges

66. DO ITYOURSELF
 https://github.com/johanjanssen/
 LCC
 LCCInstallScript

67. CONCLUSION

68. The best part!!

69. QUESTIONS?
Johan Janssen, Info Support
@johanjanssen42