This document provides information about an individual named Jarek Ratajski. It lists that he works for CSS Versicherung as a developer and wizard. It provides his email and Twitter handle. It then lists the various programming languages and technologies he has experience with. The rest of the document appears to be about architecture and challenges in scaling applications. It discusses using non-blocking architectures to process many events using few threads. It provides an overview of Lagom, a framework from Lightbend for building reactive microservices applications. It discusses entity components in Lagom like commands, events and state. It also covers reading from Cassandra and implementing read models.

1. Jarek Ratajski
CSS Versicherung
jratajski@gmail.com
@jarek000000
Lagom it's about time

2. Jarek Ratajski
Developer, wizard, anarchitectDeveloper, wizard, anarchitect
Lives in LuzernLives in Luzern
Works in CSS InsuranceWorks in CSS Insurance
C64, 6502, 68000, 8086, C++, Java, JEE, Scala, Akka, JS,C64, 6502, 68000, 8086, C++, Java, JEE, Scala, Akka, JS,
ScalaJS....ScalaJS....
jratajski@gmail.comjratajski@gmail.com @jarek000000@jarek000000

3. Agenda
●
Intro
●
Something, something - Lagom
●
End

4. Architecture of 90-ties
● Single core processors
● Small RAM ( 256 MB)
● 1000s of clients
● 10 Req / S
Motto: Conserve RAM
Result: heavy disk usage, concurrency by locks

5. 90ties revenge

6. Architecture now
● Multicores 8-20 Cores
● Huge RAM 1TB
● 100 000 Clients
● 1000 Req / s
● Cloud
Motto: Scale

7. Scaling - Amdahl's law

8. Do you know what is your AS doing?

11. Challenges
● Use multiple cores
● Do not lock
● Minimize context switching
Proposal: non blocking architecture, proces many events using only few threads

12. Non blocking architecture
Request 2
parse, call http
Request 1
parse http response
Call DB
Request 2
parse http response
Call DB
Request 2
Prosess DB result
Send response
Request 1
Prosess DB result
Send response
Http response for 1 Http response for 2 Db 2 Db 1
service
db
Http server
1
2

13. Lagom
Lighbend (Typesafe)
Creators of Akka / Play
Java 8 API
Microservices
Reactive
Cassandra
Non blocking
ConductR
Event Sourcing
CQRS
Opinionated

14. DEMO

15. Lagom project structure
● Maven (or SBT)
● Build
● Configs

16. user-api game-api score-api
user-impi user-impiuser-impi
HTTP/REST HTTP/REST
Does not have to be
implemented by LAGOM

17. Lagom – Define Service - API
public interface UsersService extends Service{
ServiceCall<NewUser, RegUserStatus> addUser(String id);
ServiceCall<LoginData, Option<Session>> login(String id);
ServiceCall<NotUsed, Option<Session>> session(String sessionId);
@Override
default Descriptor descriptor() {
return named("users").withCalls(
pathCall("/api/users/add/:id", this::addUser),
pathCall("/api/users/login/:id", this::login),
pathCall("/api/users/session/:id", this::session)
).withAutoAcl(true);
}
}

18. Lagom – Implement Service
@Override
public HeaderServiceCall<NewUser, RegUserStatus> addUser(String id) {
return (reqHeaders, postedUser) -> {
PersistentEntityRef<UserCommand> ref =
persistentEntityRegistry.refFor(UserEntity.class, id);
return ref.ask(new UserCommand.RegisterUser(id, postedUser))
.thenApply( stat -> Pair.create(ResponseHeader.OK, stat));
};
}

19. Entities - CQRS
● Commands
● Events
● State
● Behaviour
● Based on akka-actors / akka-persistence
request
command
events
state
response

20. Lagom – Commands
@Immutable
@JsonDeserialize
class RegisterUser implements UserCommand , CompressedJsonable,
PersistentEntity.ReplyType<RegUserStatus>{
public final String userId;
public final String password;
@JsonCreator
public RegisterUser(String userId, String password) {
this.userId = userId;
this.password = password;
}
}

21. Lagom – Events
@Immutable
@JsonDeserialize
final class RegisteredUser implements UserEvent {
public final String userId;
public final String password;
@JsonCreator
public RegisteredUser(String id, String password) {
this.userId = id;
this.password = password;
}
}

22. Lagom – State
@Immutable
public class UserData {
public final String id;
public final String hashedPassword;
public UserData(String id, String hashedPassword) {
this.id = id;
this.hashedPassword = hashedPassword;
}
}
@Immutable
public class UserState {
public final Option<UserData> user ;
public UserState(final Option<UserData> user) {
this.user = user;
}
public static UserState empty() {
return new UserState(Option.none());
}
}

23. Lagom - entity
public class UserEntity extends PersistentEntity<UserCommand, UserEvent, UserState> {
@Override
public Behavior initialBehavior(Optional<UserState> snapshotState) {
BehaviorBuilder b = newBehaviorBuilder(
snapshotState.orElse(UserState.empty()));
b.setEventHandler(UserEvent.RegisteredUser.class,
evt -> new UserState(Option.some(new UserData(evt.userId, evt.data.password))));
b.setCommandHandler(UserCommand.RegisterUser.class, this::handleRegisterUserCMD);
b.setReadOnlyCommandHandler( UserCommand.LoginUser.class,
(cmd,ctx) ->
ctx.reply( state()
.user.map(
u-> u.hashedPassword
.equals(cmd.data.password))
.getOrElse(false))
);
return b.build();
}
private Persist handleRegisterUserCMD(UserCommand.RegisterUser cmd, CommandContext ctx) {
if (state().user.isDefined()) {
ctx.reply(new RegUserStatus(Option.some("user exists")));
return ctx.done();
} else {
return ctx.thenPersist(new UserEvent.RegisteredUser(cmd.userId, cmd.data),
evt -> ctx.reply( new RegUserStatus(Option.none())));
}
}
}

24. Lagom - entity
public class UserEntity extends PersistentEntity<UserCommand, UserEvent, UserState> {
@Override
public Behavior initialBehavior(Optional<UserState> snapshotState) {
BehaviorBuilder b = newBehaviorBuilder(
snapshotState.orElse(UserState.empty()));
b.setEventHandler(UserEvent.RegisteredUser.class,
evt -> new UserState(Option.some(new UserData(evt.userId, evt.data.password))));
b.setCommandHandler(UserCommand.RegisterUser.class, this::handleRegisterUserCMD);
b.setReadOnlyCommandHandler( UserCommand.LoginUser.class,
(cmd,ctx) ->
ctx.reply( state()
.user.map(
u-> u.hashedPassword
.equals(cmd.data.password))
.getOrElse(false))
);
return b.build();
}
private Persist handleRegisterUserCMD(UserCommand.RegisterUser cmd, CommandContext ctx) {
if (state().user.isDefined()) {
ctx.reply(new RegUserStatus(Option.some("user exists")));
return ctx.done();
} else {
return ctx.thenPersist(new UserEvent.RegisteredUser(cmd.userId, cmd.data),
evt -> ctx.reply( new RegUserStatus(Option.none())));
}
}
}

25. Lagom - entity
public class UserEntity extends PersistentEntity<UserCommand, UserEvent, UserState> {
@Override
public Behavior initialBehavior(Optional<UserState> snapshotState) {
BehaviorBuilder b = newBehaviorBuilder(
snapshotState.orElse(UserState.empty()));
b.setEventHandler(UserEvent.RegisteredUser.class,
evt -> new UserState(Option.some(new UserData(evt.userId, evt.data.password))));
b.setCommandHandler(UserCommand.RegisterUser.class, this::handleRegisterUserCMD);
b.setReadOnlyCommandHandler( UserCommand.LoginUser.class,
(cmd,ctx) ->
ctx.reply( state()
.user.map(
u-> u.hashedPassword
.equals(cmd.data.password))
.getOrElse(false))
);
return b.build();
}
private Persist handleRegisterUserCMD(UserCommand.RegisterUser cmd, CommandContext ctx) {
if (state().user.isDefined()) {
ctx.reply(new RegUserStatus(Option.some("user exists")));
return ctx.done();
} else {
return ctx.thenPersist(new UserEvent.RegisteredUser(cmd.userId, cmd.data),
evt -> ctx.reply( new RegUserStatus(Option.none())));
}
}
}

26. Cassandra

27. Lagom – Read Side and SQL/NoSQL
● Cassandra is default Event Store from few options
● SQL DB also goes ... typically makes no sense
● There can be additional READ MODELS created for Entities (for READs SQL
makes sense)
events
state
Read side projection
Read side processor
request
response

28. Lagom – read side... writeProcessor
private CompletionStage<List<BoundStatement>> processScoreAdded(ScoreEvent.RecordAdded event) {
System.out.println("score in PROCESSOR:"+ event);
final ScoreRecord singleRecord = event.record;
return this.getSingleScore(singleRecord.userId).thenApply(
score -> {
BoundStatement bindWriteScore = writeScore.bind();
boolean won = singleRecord.result == GameResult.WON;
bindWriteScore.setInt("totalScore", score.totalScore + (won ? 5 : 0 ));
bindWriteScore.setInt("gamesWon", score.gamesWon + (won ? 1 : 0));
bindWriteScore.setInt("gamesLost",score.gamesLost + (won ? 0 : 1) );
bindWriteScore.setInt("gamesPlayed",score.gamesPlayed + 1 );
bindWriteScore.setInt("pointsScored", score.pointsScored+ singleRecord.playerScored);
bindWriteScore.setInt("pointsLost", score.pointsLost+ singleRecord.opponentScore);
bindWriteScore.setString("userId", singleRecord.userId);
System.out.println("bound for:"+singleRecord.userId);
return bindWriteScore;
}
).thenApply(bs -> Arrays.asList(bs));
}

29. Lagom – read side... read with CQL
public ServiceCall<NotUsed, List<UserScore>> getTopScores() {
return request -> {
return cassandraSession.selectAll(
"SELECT userId, " +
"totalScore, " +
"gamesWon, " +
"gamesLost, " +
"gamesPlayed, " +
"pointsScored, " +
"pointsLost FROM userScore "
)
.thenApply(allRows ->
List.ofAll(allRows)
.map(ScoreRSProcessor.getRowUserScoreFunction())
.sortBy(score ->score.totalScore)
.reverse()
.take(20)
);
};
}

30. Websocket
private Source<GameState, NotUsed> createFlow(Source<String, NotUsed> input, final String gameId) {
final PubSubRef<GameState> ref = pubSub.refFor(TopicId.of(GameState.class, gameId));
Source<GameState, NotUsed> games = ref.subscriber();
return games;
}
@Override
public ServiceCall<Source<String, NotUsed>, Source<GameState, NotUsed>> stream(final String
gameId) {
return req ->
CompletableFuture.completedFuture(createFlow(req, gameId));
}

31. Security
public HeaderServiceCall<String, Done> movePaddle(final String gameId) {
return runSecure((session, newPosition) -> {
float targetY = Float.parseFloat(newPosition);
PersistentEntityRef<GameStateCommand> ref =
persistentEntityRegistry.refFor(GameStateEntity.class, gameId);
return ref.ask(new GameStateCommand.MovePlayerPaddle(session.userId, targetY));
}, () -> Done.getInstance());
}

32. Lagom - testing
@Test
public void testDoubleCreateUser() {
withServer(defaultSetup().withCassandra(true), server -> {
UsersService service = server.client(UsersService.class);
RegUserStatus created1st = service.addUser("aaa").invoke(new NewUser("aaa")).toCompletableFuture().get(5,
SECONDS);
RegUserStatus created2nd= service.addUser("aaa").invoke(new NewUser("aaa")).toCompletableFuture().get(5,
SECONDS);
assertTrue( created1std.ok);
assertFalse( created2nd.ok);
});
}

33. Lagom programming - summary
● Java 8
● High order functions
● CompletableFuture FTW
● Immutability
● JavaSlang – perfect fit
● Fast feedback with sbt and maven(!)
● Nice tests... but slow
● Nice Documentation
● Still changing API

34. Lagom programming – very little magic
● No aspects with annotations
● Very simple DI framework Guice
● No beans – just classes
● Clean code with lagom is natural

35. Lagom alternatives
● Scala + Akka/ Akka persistence
● Ratpack + Airomem DROP DB
● Spring 5 Reactive
● JavaEE
● Spring

36. Lagom alternative - Ratpack
● Java 8 Non blocking http library
● Netty based
● Non blocking
● Not a framework
● Open source
● Do persistence on your own (like #DROPDB or async SQL or NoSQL)
● Fast tests
● More code to write
● No magic at all
● Ratpack + airomem : All you can get from single machine

37. Lagom alternative – Scala + Akka stack
● Lightbend
● Lagom is built on top of akka + play
● Scala first API
● Implementaions in Scala OK, in Java .... so so
● Lot of existing implementations, mature standard, help + support
● Professional support
● Open source
● Same as Lagom but Probably best for Scala teams

38. Lagom alternative – Spring 5 Reactive
● Comes soon
● No magic (like Spring Beans with DI) needed
● Similar to Ratpack !
● IMO Better looking API
● Some compatibility with Spring
● With better SpringData (non blocking, non magic) might be really killer platform!

40. Lagom alternatives – JavaEE or Spring
● Too much magic
● Too much locking
● Hell of getters, setters and singletons( Spring)
● Tests with mocks will test mocks
● Cleand code... with those platforms ?
● Classical state based persistence makes it easy for people
● We've seen enough!

41. Do you want to know more?
Life Beyond the Illusion of Present by
Jonas Boner
Polyglot Data by
Greg Young
Monadic Java & G o F patterns
Mario Fusco

42. Q&AJarek Ratajski
@jarek000000
jratajski@gmail.com