Probably you are curious about this thing called Reactive Programming. Reactive Programming is another programming paradigm that in most of the cases, we are not used to coding in our day-to-day work, as the imperative way is the common one. This makes learning and thinking in a reactive way harder. One of the main problems I have found when learning and reading material about Reactive Programming is that they never tackle enterprise use cases. In this session, we are going to skip the cute ideas that are normally part of a reactive programming talk and focus on how to use it in the real world. Don't be the last developer to board this train and move your reactive skills from novice to expert.

1. @alexsotob
Reactive Programming
for Real Use Cases
Alex Soto
Director of Developer Experience Red Hat
(@alexsotob)

2. @alexsotob
2
Buenas tardes, buenas noches,
señoritas y señores
To be here with you tonight.
Brings me joy, que alegria
— Miguel
“

3. @alexsotob
3
Who Am I?
Alex Soto

4. @alexsotob
System extensions
Programming
Manifesto
Streams
Asynchrony
Resilience
Elasticity
Back-Pressure
Spreadsheets
Actor
Events
Messages
Data Flows
RX Java
Responsiveness
Fibers Non-
Blocking
Reactor
Spring
MicroProfile
REACTIVE ALL THE THING
R-Socket

5. @alexsotob5
What's this?
The streets are lined with
Little creatures laughing.
— Jack Skellington
“

6. @alexsotob
Click events on steroids

7. @alexsotob
C CC C C C
click stream
C CC C CC
double click stream
buffer(100ms)
C C CC
double clicks stream
filter >=2
subscribe executes everything

8. @alexsotob
Event-Driven => Concurrent Applications
Build concurrent
applications
Reactive
programming
Reactive
streams
Non-Blocking
Asynchronous
Non-Blocking IO (Netty)
Reactive Framework
Application Code
Callbacks, RX Java,
Reactor, Co-routines...
} 1 Thread -> n concurrent
tasks

9. @alexsotob9
Proceed with
caution!!!.
— Fear
“

10. @alexsotob
From Event-Driven to Systems

11. @alexsotob
Reactive => Responsive
RESPONSIVE
ASYNC MESSAGE
PASSING
ELASTICITY RESILIENCE

12. @alexsotob
Async != multi-thread
Async == never-block

13. @alexsotob
Asynchronous & Non-Blocking execution model
Ideal
world
Task A Task
B
Task
C
Real
world
Blocking I/O
Asynchronous
execution

14. @alexsotob
Containers are about sharing and deployment density
Container Host
Threads
costs memory
cost lots of memory
cost CPU cycles
+ quotas = BOOM
The hidden truth of containers

15. @alexsotob
2020

16. @alexsotob16
On an island that I own
Tan and rested and alone
Surrounded by
enormous piles of money
— Eugene
“

17. @alexsotob17
I just don’t see how a world
that makes such a
wonderful things
could be bad?
— Ariel
“

18. @alexsotob18
Supersonic.
Subatomic.
REACTIVE.

19. @alexsotob
Quarkus = (Imperative + Reactive)/Reactive
Eclipse Vert.x / Netty
Undertow
(Servlet)
RESTEasy
(JAX-RS) Reactive
Routes
Reactive
Messaging
Reactive
Data Access
EventsMessages
HTTP

20. @alexsotob
Pagination + Filtering
Beer
Consumer
Beer
Service
getPage(1)
getPage(n)

21. @alexsotob
Pagination
Flowable<List<Beer>> beerStream = Flowable.generate(() -> 1, (page, emitter) -> {
final List<Beer> beers = beerGateway.getBeers(page);
if (beers.isEmpty()) {
emitter.onComplete();
} else {
emitter.onNext(beers);
}
return page + 1;
});
return beerStream
.flatMap(Flowable::fromIterable);
Initial Page
Get Beers
Emit Beers of Finish
Iterate to the next page
Individual Beer Is Emitted

22. @alexsotob
Pagination
@GET
@Path("/all")
@Produces(MediaType.APPLICATION_JSON)
public Publisher<Beer> getBeers() {
return beerservice.beers()
.filter(b -> b.getAbv() > 10.0);
}
~Thread
Get Beers Streams
Stream Operation

23. @alexsotob
Parallel Requests
Beer
Consumer
Beer
Service
getBeer(XXX)
getBeer(YYY)

24. @alexsotob
Parallel Requests
public Flowable<JsonValue> compareBeers(String beerA, String beerB) {
final Flowable<JsonObject> beerAInfo = beerGateway.getBeer(beerA)
.map(array -> array.get(0))
.map(this::filterContent);
final Flowable<JsonObject> beerBInfo = beerGateway.getBeer(beerB)
.map(array -> array.get(0))
.map(this::filterContent);
return beerAInfo.zipWith(beerBInfo, this::compare);
}
Get Beer Async
Get Important Fields
When Both Operations Finishes
Execute Comparison

25. @alexsotob25
A hundred thousand things to see
(Hold your breath, it gets better)
— Jasmine & Aladdin
“

26. @alexsotob26
Don’t you know
there’s part of me that
longs to go…
Into the Unknown
— Elsa
“

27. @alexsotob
HTTP => Strong Coupling

28. @alexsotob
HTTP => Uptime Coupling

29. @alexsotob
HTTP => Strong Coupling
C
B
C
B
C
B
C
B
C
B
C
B

30. @alexsotob
Messaging
Non-Blocking
Message
Passing
Elasticity
Resilience

31. @alexsotob
Data at Rest => Data At Motion
Message
Stream
Publish/
Subscribe
Request-Reply

32. @alexsotob
Quarkus = {HTTP, Messaging, Streaming}
Messaging / Streaming
Quarkus
Application Code
Container Host / Operating System
NIO HTTP Messaging
Quarkus
Application Code
Container Host / Operating System Messaging
Middleware

33. @alexsotob
Quarkus = {HTTP, Messaging, Streaming}
MicroProfile Reactive Messaging
Quarkus
Application Code
Container Host / Operating System
NIO HTTP Messaging
Quarkus
Application Code
Container Host / Operating System Messaging
Middleware
*
* Kafka or any other messaging system.

34. @alexsotob
Music Charts
Player Top Music Chart Player Top Music Chart
HTTP
Dashboard
Song Played
*
play music musicplay

35. @alexsotob
REST to Messaging
@Inject
@Channel("orders")
Emitter<String> orders;
public Order enqueue(Order order) {
orders.send(jsonb.toJson(order));
return order;
}
Send “data” to the
channel “orders”

36. @alexsotob
Processing Messages
@Incoming("orders")
@Outgoing("queue")
public CompletionStage<String> prepare(String message) {
Order order = fromJson(message, Order.class);
return makeIt(order)
.thenApply(beverage ->
PreparationState.ready(order, beverage)
);
}
Read from “orders”
Write to “queue”
Process data async*

37. @alexsotob37
A hundred thousand things to see
(Hold your breath, it gets better)
— Jasmine & Aladdin
“

38. @alexsotob38
Put on your Sunday clothes
there's lots of world
out there.
— Wall-E
“
[https://github.com/lordofthejars/rp4rp]

39. @alexsotob39
What's the lesson?
What is the take-away?
— Maui
“

40. @alexsotob40
Quarkus = {HTTP, Messaging, Streaming}
HTTP, Messaging, Streaming
Quarkus
Non-Blocking IO

41. @alexsotob41
WHAT ABOUT REACTIVE STREAMS?
@Channel(“foo”) Emitter
@Incoming(“foo”)
@Outgoing(“bar”)
@Channel(“bar”) Publisher
@Outoing(“foo”)
@Incoming(“bar”)
Publisher Processor Subscriber
Connector Connector

42. @alexsotob
Hay un amigo en mí,
cuando salgan a volar,
hay un amigo en mí
— Toy Story
“
@alexsotob
asotobue@redhat.com
http://www.lordofthejars.com/
lordofthejars