Akka Made Our Day ! JFokus 2014
Daniel Deogun & Daniel Sawano
Email: Daniel.deogun@Omegapoint.se, Daniel.Sawano@Omegapoint.se
Twitter: @DanielDeogun, @DanielSawano
A presentation at Jfokus 2014 in February 2014 in Stockholm, Sweden by Daniel Sawano
Akka Made Our Day ! JFokus 2014
Daniel Deogun & Daniel Sawano
Email: Daniel.deogun@Omegapoint.se, Daniel.Sawano@Omegapoint.se
Twitter: @DanielDeogun, @DanielSawano
Who We Are D a n i e l D e o g u n D a n i e l S a w a n o O m e g a p o i n t S t o c k h o l m - G o t h e n b u r g - M a l m o e - U m e a - N e w Y o r k
Agenda - A k k a i n a n u t s h e l l - A k k a & J a v a - D o m a i n i n f l u e n c e s - L e s s o n s l e a r n e d f r o m b u i l d i n g r e a l s y s t e m s w i t h A k k a
Akka in a Nutshell http://akka.io/
Akka in a Nutshell A c t o r s [1] By Dickelbers (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
! http://upload.wikimedia.org/wikipedia/commons/0/09/Sweden_postbox.JPG M e s s a g e s M a i l b o x [1] A c t o r S y s t e m R o u t e r s
Akka in a Nutshell A c t o r s [1] By Dickelbers (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
! http://upload.wikimedia.org/wikipedia/commons/0/09/Sweden_postbox.JPG M e s s a g e s M a i l b o x [1] A c t o r S y s t e m R o u t e r s
Akka in a Nutshell A c t o r s [1] By Dickelbers (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
! http://upload.wikimedia.org/wikipedia/commons/0/09/Sweden_postbox.JPG M e s s a g e s M a i l b o x [1] A c t o r S y s t e m R o u t e r s
Akka in a Nutshell A c t o r s [1] By Dickelbers (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
! http://upload.wikimedia.org/wikipedia/commons/0/09/Sweden_postbox.JPG M e s s a g e s M a i l b o x [1] A c t o r S y s t e m R o u t e r s
Akka in a Nutshell A c t o r s [1] By Dickelbers (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
! http://upload.wikimedia.org/wikipedia/commons/0/09/Sweden_postbox.JPG M e s s a g e s M a i l b o x [1] A c t o r S y s t e m R o u t e r s
Akka in a Nutshell A c t o r s [1] By Dickelbers (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
! http://upload.wikimedia.org/wikipedia/commons/0/09/Sweden_postbox.JPG M e s s a g e s M a i l b o x [1] A c t o r S y s t e m R o u t e r s
Our definition of
Legacy Code
Legacy
ˈ
le-g
ə
-s
ē
\
“: something that happened in the past or that comes from someone in the past ” !
Our definition of
Legacy Code
Legacy
ˈ
le-g
ə
-s
ē
\
“: something that happened in the past or that comes from someone in the past ” !
“: code that does not satisfy the characteristics of a reactive system ”
What is Legacy Code? C h a r a c t e r i s t i c s o f a r e a c t i v e s y s t e m , a s d e f i n e d b y t h e r e a c t i v e m a n i f e s t o : - r e s p o n s i v e - s c a l a b l e - r e s i l i e n t - e v e n t - d r i v e n r e a c t i v e m a n i f e s t o . o r g
Java or Scala I w a n t t o b u i l d a n a p p l i c a t i o n w i t h A k k a , s h o u l d I u s e J a v a o r S c a l a ? W e l l , i t d e p e n d s . . . [1] https://duke.kenai.com/wave/.Midsize/Wave.png.png ! [2] http://www.scala-lang.org/ [1] [2]
Java or Scala Pros & Cons A s s u m e w e w a n t t o b u i l d a m a c h i n e M t o s o l v e a p r o b l e m P w h e r e , E f f i c i e n c y i s i m p e r a t i v e S e q u e n t i a l c o m p u t a t i o n s s h a l l b e i n d e p e n d e n t I m p l e m e n t a t i o n o f M s h a l l b e p l a t f o r m i n d e p e n d e n t C o m p l e x i t y a n d b o i l e r p l a t e c o d e s h a l l b e r e d u c e d M ’ s b e h a v i o r s h a l l b e v e r i f i a b l e T i m e t o M a r k e t i s e s s e n t i a l a n d r i s k s s h a l l b e m i n i m i z e d S c o r e b o a r d J a v a : S c a l a :
Java or Scala Pros & Cons A s s u m e w e w a n t t o b u i l d a m a c h i n e M t o s o l v e a p r o b l e m P w h e r e , E f f i c i e n c y i s i m p e r a t i v e S e q u e n t i a l c o m p u t a t i o n s s h a l l b e i n d e p e n d e n t I m p l e m e n t a t i o n o f M s h a l l b e p l a t f o r m i n d e p e n d e n t C o m p l e x i t y a n d b o i l e r p l a t e c o d e s h a l l b e r e d u c e d M ’ s b e h a v i o r s h a l l b e v e r i f i a b l e T i m e t o M a r k e t i s e s s e n t i a l a n d r i s k s s h a l l b e m i n i m i z e d S c o r e b o a r d J a v a : S c a l a : I I
X
Java or Scala Pros & Cons A s s u m e w e w a n t t o b u i l d a m a c h i n e M t o s o l v e a p r o b l e m P w h e r e , E f f i c i e n c y i s i m p e r a t i v e S e q u e n t i a l c o m p u t a t i o n s s h a l l b e i n d e p e n d e n t I m p l e m e n t a t i o n o f M s h a l l b e p l a t f o r m i n d e p e n d e n t C o m p l e x i t y a n d b o i l e r p l a t e c o d e s h a l l b e r e d u c e d M ’ s b e h a v i o r s h a l l b e v e r i f i a b l e T i m e t o M a r k e t i s e s s e n t i a l a n d r i s k s s h a l l b e m i n i m i z e d S c o r e b o a r d J a v a : S c a l a : I I I I
X X
Java or Scala Pros & Cons A s s u m e w e w a n t t o b u i l d a m a c h i n e M t o s o l v e a p r o b l e m P w h e r e , E f f i c i e n c y i s i m p e r a t i v e S e q u e n t i a l c o m p u t a t i o n s s h a l l b e i n d e p e n d e n t I m p l e m e n t a t i o n o f M s h a l l b e p l a t f o r m i n d e p e n d e n t C o m p l e x i t y a n d b o i l e r p l a t e c o d e s h a l l b e r e d u c e d M ’ s b e h a v i o r s h a l l b e v e r i f i a b l e T i m e t o M a r k e t i s e s s e n t i a l a n d r i s k s s h a l l b e m i n i m i z e d S c o r e b o a r d J a v a : S c a l a : I I I I I I
X X X
Java or Scala Pros & Cons A s s u m e w e w a n t t o b u i l d a m a c h i n e M t o s o l v e a p r o b l e m P w h e r e , E f f i c i e n c y i s i m p e r a t i v e S e q u e n t i a l c o m p u t a t i o n s s h a l l b e i n d e p e n d e n t I m p l e m e n t a t i o n o f M s h a l l b e p l a t f o r m i n d e p e n d e n t C o m p l e x i t y a n d b o i l e r p l a t e c o d e s h a l l b e r e d u c e d M ’ s b e h a v i o r s h a l l b e v e r i f i a b l e T i m e t o M a r k e t i s e s s e n t i a l a n d r i s k s s h a l l b e m i n i m i z e d S c o r e b o a r d J a v a : S c a l a : I I I I I I I
X X X X
Java or Scala Pros & Cons A s s u m e w e w a n t t o b u i l d a m a c h i n e M t o s o l v e a p r o b l e m P w h e r e , E f f i c i e n c y i s i m p e r a t i v e S e q u e n t i a l c o m p u t a t i o n s s h a l l b e i n d e p e n d e n t I m p l e m e n t a t i o n o f M s h a l l b e p l a t f o r m i n d e p e n d e n t C o m p l e x i t y a n d b o i l e r p l a t e c o d e s h a l l b e r e d u c e d M ’ s b e h a v i o r s h a l l b e v e r i f i a b l e T i m e t o M a r k e t i s e s s e n t i a l a n d r i s k s s h a l l b e m i n i m i z e d S c o r e b o a r d J a v a : S c a l a : I I I I I I I I
X X X X X
Java or Scala Pros & Cons A s s u m e w e w a n t t o b u i l d a m a c h i n e M t o s o l v e a p r o b l e m P w h e r e , E f f i c i e n c y i s i m p e r a t i v e S e q u e n t i a l c o m p u t a t i o n s s h a l l b e i n d e p e n d e n t I m p l e m e n t a t i o n o f M s h a l l b e p l a t f o r m i n d e p e n d e n t C o m p l e x i t y a n d b o i l e r p l a t e c o d e s h a l l b e r e d u c e d M ’ s b e h a v i o r s h a l l b e v e r i f i a b l e T i m e t o M a r k e t i s e s s e n t i a l a n d r i s k s s h a l l b e m i n i m i z e d S c o r e b o a r d J a v a : S c a l a : I I I I I I I I
X X X X X X
Akka All or nothing? E l a s t i c D i s t r i b u t e d D e c e n t r a l i z e d R e s i l i e n t Akka S u p e r v i s i o n M o d u l a r i z a t i o n I n t e g r a t i o n P a r a l l e l i s m A b s t r a c t i o n l e v e l
Akka All or nothing? E l a s t i c D i s t r i b u t e d D e c e n t r a l i z e d R e s i l i e n t Akka S u p e r v i s i o n M o d u l a r i z a t i o n I n t e g r a t i o n P a r a l l e l i s m A b s t r a c t i o n l e v e l
Akka All or nothing? E l a s t i c D i s t r i b u t e d D e c e n t r a l i z e d R e s i l i e n t Akka S u p e r v i s i o n M o d u l a r i z a t i o n I n t e g r a t i o n P a r a l l e l i s m A b s t r a c t i o n l e v e l
Akka All or nothing? E l a s t i c D i s t r i b u t e d D e c e n t r a l i z e d R e s i l i e n t Akka S u p e r v i s i o n M o d u l a r i z a t i o n I n t e g r a t i o n P a r a l l e l i s m A b s t r a c t i o n l e v e l
Akka All or nothing? E l a s t i c D i s t r i b u t e d D e c e n t r a l i z e d R e s i l i e n t Akka S u p e r v i s i o n M o d u l a r i z a t i o n I n t e g r a t i o n P a r a l l e l i s m A b s t r a c t i o n l e v e l
Akka All or nothing? E l a s t i c D i s t r i b u t e d D e c e n t r a l i z e d R e s i l i e n t Akka S u p e r v i s i o n M o d u l a r i z a t i o n I n t e g r a t i o n P a r a l l e l i s m A b s t r a c t i o n l e v e l
Reactive in a Legacy Environment? B l o c k i n g B l o c k i n g B l o c k i n g B l o c k i n g A B C D I s i t p o s s i b l e t o r e p l a c e D b y a c o m p o n e n t i m p l e m e n t e d w i t h A k k a ?
Debugger
Friend or Foe?
W e o f t e n g e t t h e q u e s t i o n :
!
“ T h e a s y n c h r o n y i n A k k a m a k e s i t v e r y h a r d t o
u s e t h e d e b u g g e r , A m I d o i n g i t w r o n g ? ”
debugger in
Legacy Design
L e g a c y D e s i g n
O b j e c t A
O b j e c t B
O b j e c t N
debugger in
Legacy Design
L e g a c y D e s i g n
O b j e c t A
O b j e c t B
debugger in
Legacy Design
L e g a c y D e s i g n
O b j e c t A
O b j e c t B
O b j e c t N
P l a c e a b r e a k p o i n t i n N t o f i n d o u t
- W h i c h v a l u e c a u s e d t h e c r a s h ?
- W h o c r e a t e d i t ?
debugger in
Reactive Design R e a c t i v e d e s i g n B r e a k p o i n t i n a c t o r N
Supervision W e ’ r e r e a c t i v e
Supervision o h n o I ’ m b l o c k e d b u t I ’ m s t i l l p r e t t y
W e ’ r e r e a c t i v e
Supervision A s y n c h r o n o u s
Supervision A s y n c h r o n o u s F a i l u r e
Supervision S y n c h r o n o u s B l o c k i n g c a l l
Supervision S y n c h r o n o u s B l o c k i n g c a l l
Supervision S y n c h r o n o u s B l o c k i n g c a l l S e n d f a i l u r e
Supervision S y n c h r o n o u s B l o c k i n g c a l l S e n d f a i l u r e
Supervision
!
private ActorRef targetActor; ! private ActorRef caller; ! private AskParam askParam; ! private Cancellable timeoutMessage; ! ! @Override ! public SupervisorStrategy supervisorStrategy() { ! return new OneForOneStrategy(0, Duration.Zero(), new Function<Throwable, SupervisorStrategy.Directive>() { ! public SupervisorStrategy.Directive apply(Throwable cause) { ! caller.tell(new Failure(cause), self()); ! return SupervisorStrategy.stop(); ! } ! }); ! } ! ! @Override ! public void onReceive(final Object message) throws Exception { ! if (message instanceof AskParam) { ! askParam = (AskParam) message; ! caller = sender(); ! targetActor = context().actorOf(askParam.props); ! context().watch(targetActor); ! targetActor.forward(askParam.message, context()); ! final Scheduler scheduler = context().system().scheduler(); ! timeoutMessage = scheduler.scheduleOnce(askParam.timeout.duration(), self(), new AskTimeout(), context().dispatcher(), null); ! } ! else if (message instanceof Terminated) { ! sendFailureToCaller(new ActorKilledException("Target actor terminated.")); ! timeoutMessage.cancel(); ! context().stop(self()); ! } ! else if (message instanceof AskTimeout) { ! sendFailureToCaller(new TimeoutException("Target actor timed out after " + askParam.timeout.toString())); ! context().stop(self()); ! } ! else { ! unhandled(message); ! } ! } ! ! private void sendFailureToCaller(final Throwable t) { ! caller.tell(new Failure(t), self()); ! }
Supervision - W r i t e l e g a c y c o d e - U s e A k k a a c t o r s
Supervision - W r i t e l e g a c y c o d e - U s e A k k a a c t o r s S e q u e n t i a l d o e s n o t i m p l y s y n c h r o n i c i t y
The Shared Mutable State Trap K e e p i n g s t a t e b e t w e e n m e s s a g e s i n a n a c t o r i s e x t r e m e l y d a n g e r o u s b e c a u s e i t m a y c a u s e a s h a r e d m u t a b l e s t a t e ! ! !
The Shared Mutable State Trap A c t o r P r o p e r t i e s - O n e m e s s a g e q u e u e - O n l y o n e m e s s a g e i s p r o c e s s e d a t a t i m e - M e s s a g e s a r e p r o c e s s e d i n o r d e r r e c e i v e d - A n a c t o r m a y c h o o s e t o d i v i d e a n d c o n q u e r a t a s k b y c a l l i n g o t h e r a c t o r s
The Shared Mutable State Trap R o u t e r A c t o r s m a y b e g r o u p e d i n a r o u t e r P r o p e r t i e s - M e s s a g e s a r e d i s t r i b u t e d a m o n g a c t o r s a c c o r d i n g t o s o m e m e s s a g e d e l i v e r y s c h e m e , e g R o u n d R o b i n o r S m a l l e s t M a i l b o x ! - A r o u t e r m a y r e c e i v e a l o t o f m e s s a g e s
The Shared Mutable State Trap - A s t a t e f u l a c t o r i s p a r t o f a r o u t e r ! - I t u s e s d i v i d e a n d c o n q u e r t o s o l v e i t s t a s k A c t o r w i t h s t a t e S c e n a r i o
The Shared Mutable State Trap A c t o r w i t h s t a t e - E a c h m e s s a g e r e c i v e d f r o m t h e r o u t e r r e s e t s t h e s t a t e ! - N e w m e s s a g e s a r e i n t e r m i x e d w i t h c h i l d r e s p o n s e s ! - H e n c e , w e h a v e a s h a r e d m u t a b l e s t a t e S c e n a r i o
The Shared Mutable State Trap S o l u t i o n - E a c h r e q u e s t s e n t b y t h e r o u t e r r e s u l t s i n a “ G a t h e r ” a c t o r ! - T h e G a t h e r a c t o r i s r e s p o n s i b l e f o r c o l l e c t i n g t h e r e s u l t ! - A G a t h e r a c t o r i s N E V E R r e u s e d G a t h e r a c t o r r e s u l t
Key Take-Aways - I t ’ s v e r y e a s y t o a c c i d e n t a l l y f a l l b a c k t o s e q u e n t i a l “ t h i n k i n g ” w i t h s t a t e ! - O f t e n o n e d o e s n o t r e a l i z e t h i s u n t i l t h e s y s t e m i s p l a c e d u n d e r h e a v y l o a d ! - T r y t o a v o i d s t a t e !
Readability B y V a r i o u s . E d i t e d b y : W H M a w a n d J D r e d g e ( A b a n d o n e d l i b r a r y c l e a r a n c e . S e l f p h o t o g r a p h e d . ) [ P u b l i c d o m a i n ] , v i a W i k i m e d i a C o m m o n s
Implications of untyped actors ! A k k a a c t o r s a r e u n t y p e d - b y d e s i g n ! ! public void onReceive(Object message)
Implications of untyped actors ! A k k a a c t o r s a r e u n t y p e d - b y d e s i g n - R e a d a b i l i t y - N o s u p p o r t f r o m c o m p i l e r / I D E ! ! public void onReceive(Object message)
Message Handling V 1.0 ! ! @Override ! public void onReceive(Object message) { ! if (message instanceof SomeMessage) { ! doStuff(); ! } ! else { ! unhandled(message); ! } ! } !
V 1.0 - If-else contd. ! ! @Override ! public void onReceive(Object message) { ! if (message instanceof SomeMessage) { ! doStuff(); ! } ! else if (message instanceof SomeOtherMessage) { ! doSomeOtherStuff(); ! } ! else { ! unhandled(message); ! } ! } !
V 1.0 - If-else mess ! ! @Override ! public void onReceive(Object message) { ! if (message instanceof SomeMessage) { ! doStuff(); ! } ! else if (message instanceof SomeOtherMessage) { ! doSomeOtherStuff(); ! } ! else if (message instanceof YetAnother Message) { ! doEvenMore Stuff(); ! } ! else { ! unhandled(message); ! } ! } !
Evolution of message handling ! ! ! ! @Override ! public void onReceive(Object message) { ! ... ! } ! ! h t t p : / / u p l o a d . w i k i m e d i a . o r g / w i k i p e d i a / c o m m o n s / t h u m b / 6 / 6 9 / H u m a n _ e v o l u t i o n . s v g / 2 0 0 0 p x - H u m a n _ e v o l u t i o n . s v g . p n g
V 2.0 - Overloading ! public void onMessage(SomeMessage message) {...} ! ! public void onMessage(SomeOtherMessage message) {...}
V 2.0 - Overloading ! public void onMessage(SomeMessage message) {...} ! ! public void onMessage(SomeOtherMessage message) {...} ! @Override ! public void onReceive(Object message) { ! ... ! ! methods.get(message.getClass()).invoke(this, message); ! ! ... ! } !
V 2.1 - Annotations ! ! class Worker extends BaseActor { !
!
@Response !
public void onMessage(SomeMessage message) {...} ! ! ! public void onMessage(SomeOtherMessage message) {...} ! }
V 3.0 - Contract
!
!
!
interface Messages {
!
!
void doSomething
(SomeMessage message);
!
!
void doSomethingElse
(SomeOtherMessage message);
!
!
}
!
!
!
!
V 3.0 - Contract
!
!
!
interface Messages {
!
!
void doSomething
(SomeMessage message);
!
!
void doSomethingElse
(SomeOtherMessage message);
!
!
}
!
!
!
!
!
SomeActor extends BaseActor implements Messages {...}
!
V 3.0 - Contract ! ! class Worker extends BaseActor implements Messages { !
! ! public void handleResponse (SomeMessage message) {...} ! ! ! public void handleRequest(SomeOtherMessage message) {...} ! ! }
V 3.0 - Contract ! ! BaseActor extends UntypedActor { ! ! BaseActor () { ! methodDelegate = new MethodDelegate(this); ! } ! ! @Override ! public void onReceive(Object message) { ! if (methodDelegate.onReceive(message)) { ! return; ! } ! unhandled(message); ! } ! } !
Before ! class Worker extends BaseActor implements Messages { !
@Override !
public void onReceive(Object message) { !
if (message instanceof SomeMessage) { !
doStuff(); !
}
!
else if (message instanceof SomeOtherMessage) { !
doSomeOtherStuff(); ! } ! else if (message instanceof YetAnother Message) { ! doEvenMore Stuff(); !
}
!
else { !
unhandled(message); !
}
!
After
!
!
class Worker extends
BaseActor implements Messages {
!
!
public void handleResponse(SomeMessage message) {
!
doStuff();
!
} ! ! public void handleRequest(SomeOtherMessage message) { ! doSomeOtherStuff(); ! } ! ! public void process(YetAnotherMessage message) { ! doEvenMoreStuff(); ! } ! } !
Conclusions - C o n t r a c t s t o e x p l i c i t l y d e f i n e b e h a v i o r w o r k s p r e t t y w e l l - C a n b e a u s e f u l t o o l i n y o u r t o o l b o x - S c a l a c a n g i v e s i m i l a r s u p p o r t v i a t r a i t s & m a t c h
Testing Akka Code I n t e r a c t b y s e n d i n g m e s s a g e s B D D S c e n a r i o s I n t e g r a t i o n t e s t s
Scenarios C a s e A 1 : S o r t a n y s e q u e n c e o f n u m b e r s i n i n c r e a s i n g o r d e r ! ! G i v e n a s e q u e n c e o f n u m b e r s i n d e c r e a s i n g o r d e r ! W h e n a p p l y i n g t h e s o r t a l g o r i t h m ! T h e n t h e r e s u l t i n g s e q u e n c e o f n u m b e r s i s i n i n c r e a s i n g o r d e r
The Test ! ! ! ! @Test ! ! public void case A1() { ! ! !! ! g i v e n ( s e q u e n c e ( 9 , 8 , 7 , 6 , 5 , 4 , 3 , 2 , 1 , 0 ) ) ; !
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! !! ! w h e n S o r t i n g (); !
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! !! ! t h e n R e s u l t I s ( s e q u e n c e ( 0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ) ); ! ! } !
Key Take-Aways - I t ’ s p o s s i b l e t o u s e A k k a i n l e g a c y c o d e - A k k a i s S c a l a & J a v a c o m p l i a n t - A k k a i s a t o o l k i t w i t h a l o t o f g o o d i e s - S t o p w r i t i n g l e g a c y c o d e
T h a n k y o u @ D a n i e l D e o g u n @ D a n i e l S a w a n o
