A social game, by it’s nature can spread very quickly to a large user audience. Since a game is typically interactive, the speed of retrieving information needed for the user’s interactions with the system is critical. Applications which exclusively rely on synchronous data access, very often hit a scalability wall, when things get slow and their thread pools are exhausted. New paradigms like reactive programming alleviate this and provide extensive tool sets to deal with the ever growing demands of web applications. This talk: – Describes why Couchbase is the most appropriate solution for many video game and gaming use cases. – Shows how to build scalable and reactive applications by making use of the Couchbase Java SDK 2.x, RxJava library and Spring Framework 5.

1. Building reac-ve game engine
with Spring 5 & Couchbase
Alex Derkach
Senior So0ware Engineer @ Play7ka

2. @alexsderkach
‣ Java addict since ’12
‣ SSE @ Slotomania Feature Team
‣ Ac7ve Couchbase & Spring user
‣ All things reac7ve & distributed
2h>p://alexsderkach.io
slides

3. Plan for today
3
‣ Why Couchbase + Quick Overview
‣ Reac7ve founda7on behind Spring 5
‣ Demonstra7on & Case Study
‣ Summary

4. Applica-on Layer
Old-School Architecture
4
App App
App App
App App
Read/Write
Requests
RDBMS

5. Individual Memcached NodesApplica-on Layer
Old-School Architecture
5
App App
App App
App App
Cache Misses &
Write Requests
RDBMS
Read/Write
requests
RDBMS

6. 6

7. Video game is not ‘yet another web app’
7
‣ Rapid Fall or Growth
‣ Responsiveness will brake you
‣ Always ON
‣ Flexible Data Model

8. It all comes to this…
8

9. What is Couchbase?
9
‣ Key-Document storage
‣ Consistent high performance
‣ Scale with single “push” buTon
‣ Zero-down7me opera7ons

10. Server
10
Couchbase Architecture
Cluster
Manager
Data Service
Index Service
Query Service
Cache
Storage
Server
Cluster
Manager
Data Service
Index Service
Query Service
Cache
Storage
Server
Cluster
Manager
Data Service
Index Service
Query Service
Cache
Storage
Server
Cluster
Manager
Data Service
Index Service
Query Service
Cache
Storage
Server
Cluster
Manager
Data Service
Index Service
Query Service
Cache
Storage
Couchbase Cluster

11. Server
11
Couchbase Architecture
Cluster
Manager
Data Service
Cache
Storage
Server
Cluster
Manager
Data Service
Cache
Storage
Server
Cluster
Manager
Query Service
Cache
Storage
Server
Cluster
Manager
Index Service
Cache
Storage
Server
Cluster
Manager
Index Service
Cache
Storage
Couchbase Cluster

12. 12
Example Use Case: Leaderboard
SELECT * FROM `scores`
WHERE roundId = 10
ORDER BY score DESC
LIMIT 3
Data
Service
Index Service
Query Service

13. Couchbase SDK
13
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

14. Couchbase SDK
14
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

15. Couchbase SDK
15
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

16. Couchbase SDK
16
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

17. Couchbase SDK
17
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

18. Couchbase SDK
18
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

19. Couchbase SDK
19
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

20. Couchbase SDK
20
‣ RxJava 1
‣ CRUD
‣ N1QL
‣ Map/Reduce
‣ Administra7on
bucket
.get("whiskey")
.onErrorResumeNext(bucket.getFromReplica("whiskey", ReplicaMode.ALL))
.first()
.map(doc -> doc.content().getString("name"))
.timeout(2, TimeUnit.SECONDS)
.doOnError(System.err::println)
.onErrorReturn(error -> "Not found!")

21. 21

22. 22
Couchbase
Connector
wait for events
handle events
Thread
get(“user::1”)
result
RUNNING
RUNNING
BLOCKED
Couchbase

23. 23
public interface Publisher<T> {
void subscribe(Subscriber<? super T> s);
}
public interface Subscriber<T> {
void onSubscribe(Subscription s);
void onNext(T t);
void onError(Throwable t);
void onComplete();
}
public interface Subscription {
void request(long n);
void cancel();
}
public interface Processor<T, R> extends Subscriber<T>, Publisher<R> {
}
h>ps://github.com/reac-ve-streams/reac-ve-streams-jvm
Let’s build Reac-ve Framework!

24. DIY - Reac-ve Framework
24
1. Should work with RS Java Specifica7on
2. Address the reentrance
3. Address thread safety
4. Address back-pressure
5. Address state
6. For Many-To-One Flows, implement merging
7. For One-To-Many, implement broadcas7ng
8. …
h>ps://github.com/reac-ve-streams/reac-ve-streams-jvm

25. DIY - Reac-ve Framework
25
1. Should work with RS Java Specifica7on
2. Address the reentrance
3. Address thread safety
4. Address back-pressure
5. Address state
6. For Many-To-One Flows, implement merging
7. For One-To-Many, implement broadcas7ng
8. …
h>ps://github.com/reac-ve-streams/reac-ve-streams-jvm

26. 26

27. 27
MySQL
Thread
RUNNING
BLOCKED
Couchbase
User Service
Payment Service
Twitter API
BLOCKED
BLOCKED
BLOCKED
BLOCKED
RUNNING
RUNNING
RUNNING
3rd party

28. Spring 5
28
‣ Based on Reactor Core 3
‣ Reac7ve HTTP Server Abstrac7on
‣ Compa7ble with RxJava 1 & 2
‣ Compa7ble with Java 9
‣ Many more!

29. 29
‣ Func7onal, declara7ve programming model
‣ Combine, transform, reduce sequences (500+ methods)
‣ Reac7ve Streams ready
‣ Focus on what, not how
Reactor 3 Crash Course
Flux / Mono Subscriber
0..N Data
+ 0..1 (Error, Completed)
Backpressure
regulation

30. 30
Learning to Flux
OR Flux.create(sink -> *blocking call*);Mono.create(sink -> *blocking call*);

31. 31
Learning to Flux
Mono.create(sink -> {
val result = repository.findOne(1L);
if (result.isPresent()) {
sink.success(result.get());
} else {
sink.error(new UserNotFoundException(id));
}
})
.subscribe(System.out::println);
Flux.create(sink -> *blocking call*);Mono.create(sink -> *blocking call*); OR

32. 32
Learning to Flux
Mono.create(sink -> {
val result = repository.findOne(1L);
if (result.isPresent()) {
sink.success(result.get());
} else {
sink.error(new UserNotFoundException(id));
}
})
.subscribe(System.out::println);
Flux.create(sink -> *blocking call*);Mono.create(sink -> *blocking call*);
Flux.create(sink -> {
val ids = asList(1L, 2L, 3L);
val result = userRepository.findAll(ids);
for (User user : result) {
sink.next(user);
}
sink.complete();
})
.subscribe(System.out::println);
OR

33. 33
Flux.create(..., );
enum OverflowStrategy {
// Completely ignore downstream backpressure requests.
IGNORE,
// Signal an IllegalStateException when the downstream
can't keep up
ERROR,
// Drop the incoming signal if the downstream is not
ready to receive it.
DROP,
// Downstream will get only the latest signals from
upstream.
LATEST,
// Buffer all signals if the downstream can't keep up.
BUFFER
}
Backpressure

34. 34
Flux.<User>create(sink -> {
userRepository.findAll(ids).forEach(sink::next);
sink.complete();
})
.filter(user -> user.getGender() == MALE)
.map(user -> new User(user.getId(), user.getName().toUpperCase()))
.buffer(20)
.flatMap(users ->
Flux.create(sink -> {
userRepository.save(users).forEach(sink::next);
sink.complete();
})
.subscribeOn(Schedulers.elastic())
)
.subscribeOn(Schedulers.elastic())
.subscribe(System.out::println, System.err::println);
I have a Flux. What’s next?

35. 35
Flux.<User>create(sink -> {
userRepository.findAll(ids).forEach(sink::next);
sink.complete();
})
.filter(user -> user.getGender() == MALE)
.map(user -> new User(user.getId(), user.getName().toUpperCase()))
.buffer(20)
.flatMap(users ->
Flux.create(sink -> {
userRepository.save(users).forEach(sink::next);
sink.complete();
})
.subscribeOn(Schedulers.elastic())
)
.subscribeOn(Schedulers.elastic())
.subscribe(System.out::println, System.err::println);
I have a Flux. What’s next?

36. 36
Be Blocking or Non-Blocking?

37. 37
Be Blocking or Non-Blocking?
@Test
public void testEmojiSource() {
Flux<String> source = emojiSource();
Iterable<String> values = source.toIterable();
assertEquals(asList("🙈", "🙉", "🙊"), values);
}
@Test
public void testWelcomeSource() {
Mono<String> source = welcomeSource();
String value = source.block();
assertEquals("Hello", value);
}
Non-Blocking to Blocking

38. 38
Be Blocking or Non-Blocking?
@Test
public void testEmojiSource() {
Flux<String> source = emojiSource();
Iterable<String> values = source.toIterable();
assertEquals(asList("🙈", "🙉", "🙊"), values);
}
@Test
public void testWelcomeSource() {
Mono<String> source = welcomeSource();
String value = source.block();
assertEquals("Hello", value);
}
Non-Blocking to Blocking Blocking to Non-Blocking

40. 40
spring-web
Jetty
Netty
Tomcat
Undertow
HttpServlet
Request|Response
HttpServer
Request|Response
HttpServlet
Request|Response
HttpServerExchange
🍒
ServerHttp
Request|Response
1
1
1
1
<interface>
WebHandler

41. 41
spring-web
Dispatcher
Handler
Jetty
Netty
Tomcat
Undertow
HttpServlet
Request|Response
HttpServer
Request|Response
HttpServlet
Request|Response
HttpServerExchange
🍒
ServerHttp
Request|Response
1
1
1
1
public interface HandlerMapping {
Mono<Object> getHandler( 🍒);
}
public interface HandlerAdapter {
boolean supports(Object handler);
Mono<HandlerResult> handle( 🍒, handler);
}
2
3
spring-webflux
<interface>
WebHandler
public interface HandlerMethodArgumentResolver {
boolean supportsParameter(MethodParameter);
Mono< 🍷> resolveArgument(MethodParameter, 🍒);
}
4 handler.invoke(Mono< 🍷>...);
5

42. 42
spring-web spring-webflux
@RestController
public class UserController {
@GetMapping("/users/{id}")
public User get(long id) { }
@PostMapping("/users/")
public User create(User user) { }
@PutMapping("/users/{id}")
public User update(long id, User user) { }
@DeleteMapping("/users/{id}")
public User delete(long id) { }
}
@RestController
public class UserController {
@GetMapping("/users/{id}")
public User get(long id) { }
@PostMapping("/users/")
public User create(User user) { }
@PutMapping("/users/{id}")
public User update(long id, User user) { }
@DeleteMapping("/users/{id}")
public User delete(long id) { }
}

43. 43
spring-web spring-webflux
@RestController
public class UserController {
@GetMapping("/users/{id}")
public User get(long id) { }
@PostMapping("/users/")
public User create(User user) { }
@PutMapping("/users/{id}")
public User update(long id, User user) { }
@DeleteMapping("/users/{id}")
public User delete(long id) { }
}
@RestController
public class UserController {
@GetMapping("/users/{id}")
public Mono<User> get(long id) { }
@PostMapping("/users/")
public Mono<User> create(Mono<User> user) { }
@PutMapping("/users/{id}")
public Mono<User> update(long id,
Mono<User> user) { }
@DeleteMapping("/users/{id}")
public Mono<User> delete(long id) { }
}

44. DEMO

45. 45
Flux against the world
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

46. 46
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

47. 47
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

48. 48
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

49. 49
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

50. 50
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

51. 51
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

52. 52
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

53. 53
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

54. 54
Flux against the world
composable lazy reusable async cached push
back-
pressure
operator
fusion
CompletableFuture ✔ ✘ ✔ ✔ ✔ ✔ ✘ ✘
Stream ✔ ✔ ✘ ✘ ✘ ✘ ✘ ✘
Optional ✔ ✘ ✔ ✘ ✔ ✘ ✘ ✘
Observable (RxJava 1) ✔ ✔ ✔ ✔
✔
*.cache()
✔
✔
*.onBackpressure
*()
✘
Observable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✘ ✔
Flowable (RxJava 2) ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
Flux ✔ ✔ ✔ ✔
✔
*.cache()
✔ ✔ ✔
h>p://alexsderkach.io/comparing-java-8-rxjava-reactor/

55. 55
Automa-c Op-miza-ons
‣ Macro-fusion - replacing 2+ subsequent operators with a single operator:
1. map(A) = B
2. map(B) = C ƒ(A) = D
3. filter(C) = D

56. 56
‣ Macro-fusion - replacing 2+ subsequent operators with a single operator:
1. map(A) = B
2. map(B) = C ƒ(A) = D
3. filter(C) = D
‣ Micro-fusion - operators that end in an output queue and operators star7ng with
a front-queue could share the same Queue instance
1. 0..100 = B
2. map(B) = C [0..100] <-> map <-> groupBy <-> 🙄
3. groupBy(C) = D
Automa-c Op-miza-ons
push
queuequeue request(1) request(1)
push
request(1)
push

57. ‣ Macro-fusion - replacing 2+ subsequent operators with a single operator:
1. map(A) = B
2. map(B) = C ƒ(A) = D
3. filter(C) = D
‣ Micro-fusion - operators that end in an output queue and operators star7ng with
a front-queue could share the same Queue instance
1. 0..100 = B
2. map(B) = C [0..100] <- map <-> groupBy <- 🙄
3. groupBy(C) = D
57
Automa-c Op-miza-ons
poll
queuequeue
poll
request(1)
push

58. 58
Flux against the world
‣ Stream, Op-onal, CompletableFuture - solve specific tasks
‣ Reac-ve Libraries are universal

59. 59
Reactor Core
RxJava
org.reac-vestreams
reac-ve-streams
1.0.0
Spring 5
Reactor
Kaoa
Spring
Integra-on
Add-ons
Couchbase
Hystrix

61. 61
‣ Pipeline = steps of transforma-ons
How do I test? #unit

62. 62
How do I test? #unit
🛴 🏍 🚐
transforma-on #1 transforma-on #2
‣ Pipeline = steps of transforma-ons

63. 63
How do I test? #unit
Input ExpectedTransformer
🛴 🏍 🚐
transforma-on #1 transforma-on #2
‣ Pipeline = steps of transforma-ons

64. 64
How do I test? #unit
🛴 🏍 🚐
transforma-on #1 transforma-on #2
‣ Pipeline = steps of transforma-ons
Input ExpectedTransformer

65. @Test
public void testEmojiSource() {
Flux<String> source = emojiSource();
Iterable<String> values = source.toIterable();
assertEquals(asList("🙈", "🙉", "🙊"), values);
}
@Test
public void testWelcomeSource() {
Mono<String> source = welcomeSource();
String value = source.block();
assertEquals("Hello", value);
}
65
How to verify expecta-ons?
h>ps://projectreactor.io/docs/core/release/reference/docs/index.html#tes-ng
1
@Test
public void testEmojiSource() {
Flux<String> source = emojiSource();
StepVerifier.create(source)
.expectNext("🙈", "🙉", "🙊")
.as("expect 3 more")
.expectNextCount(3)
.thenAwait(Duration.ofSeconds(3))
.expectNextMatches(v -> v.startsWith("O_O"))
.as("expect non empty batch")
.thenConsumeWhile(v -> !v.isEmpty())
.expectNextCount(1)
.verifyComplete();
}
2
3
1
2
3
convert to synchronous use StepVerifier
1
3
2
🏍

66. 66
How to generate input?🛴
@Test
public void testEmojiSource() {
Flux<String> source = Flux.just("🙈", "🙉", "🙊");
Iterable<String> values = source.toIterable();
assertEquals(asList("🙈", "🙉", "🙊"), values);
}
@Test
public void testWelcomeSource() {
Mono<String> source = Mono.just("Hello");
String value = source.block();
assertEquals("Hello", value);
}

67. 67
How to generate input?
Emit specific signals with TestPublisher<T>
‣ next(T…) will trigger 1..N onNext signals
‣ emit(T…) will do the same & complete
‣ complete() will terminate with onComplete signal
‣ error(Throwable) will terminate with an onError signal
🛴

68. 68
How to get pre>y stack-trace?
Ac-vate debug mode
Hooks.onOperator(Hooks.OperatorHook::operatorStacktrace);
Error has been observed by the following operator(s):
|_ Flux.map(FakeRepository.java:27)
|_ Flux.map(FakeRepository.java:28)
|_ Flux.filter(FakeUtils1.java:29)
|_ Flux.transform(GuideDebuggingExtraTests.java:41)
|_ Flux.elapsed(FakeUtils2.java:30)
|_ Flux.transform(GuideDebuggingExtraTests.java:42)

69. 69
How do I test Couchbase? #integra-on
without N1QL with N1QL
OR

70. 70
Future
‣ Flow API - Java 9
‣ Non-blocking JDBC spec (Java 10?)
‣ More non-blocking Spring modules
‣ …

71. Summary
71
‣ K-V Storage - perfect for video games
‣ Design Non-Blocking by Default
‣ RxJava and Reactor are friends
‣ Spring unites everyone

72. References
72
‣ Why Couchbase chose RxJava
hTps://goo.gl/dWeS35
‣ Reac7ve Spring by Josh Long
hTps://goo.gl/EXtJrB
‣ Developing Reac7ve applica7ons with Reac7ve Streams
hTps://goo.gl/eeNaAh
‣ Spring Boot 2.0 change-log
hTps://goo.gl/j8HFuY

73. 2
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