This document discusses bringing reactive programming to enterprise developers. It defines reactive as responding to stimuli without blocking. Reactive programming uses non-blocking I/O and callbacks to build concurrent and distributed systems that are responsive, message-driven, and resilient. The document advocates using reactive techniques with messaging systems like Kafka to build distributed applications and services that can handle failures and elastic workloads. It presents the Quarkus framework as unifying imperative and reactive programming for Java developers.

1. Bringing Reactive to Enterprise Developers
Clement Escoffier, Red Hat, @clementplop

2. What is Reactive?
Do we need this new thing?

3. reactive | rēˈaktiv |
adjective
showing a response to a stimulus: pupils are reactive to light.
• acting in response to a situation rather than creating or controlling it: a
proactive rather than a reactive approach.
• having a tendency to react chemically: nitrogen dioxide is a highly reactive
gas.
• Physiology showing an immune response to a specific antigen.
...
https://www.oxfordlearnersdictionaries.com/definition/english/reactive

4. reactive | rēˈaktiv |
adjective
showing a response to a stimulus: pupils are reactive to light.
• acting in response to a situation rather than creating or controlling it: a
proactive rather than a reactive approach.
• having a tendency to react chemically: nitrogen dioxide is a highly reactive
gas.
• Physiology showing an immune response to a specific antigen.
...
• Software application reacting to stimuli such as user inputs, messages,
and failures

5. What is Reactive?
Do we need this new thing?

6. Events
Signals
Failures
Is Reactive == Event-Driven ?

7. Events
Signals
Failures
Is Reactive == Event-Driven ?
EJBs
Message-Driven Beans
CDI Observers

8. Event-Driven with a different concurrency model
Non-Blocking IO (Netty)
Reactive Framework
Application Code
Callbacks, RX,
Co-routines...
} 1 Thread
Reactive
programming
Non-Blocking IO
Build concurrent
applications

9. FROM EVENT-DRIVEN TO SYSTEMS

10. “A distributed system is one in which
the failure of a computer you didn't
even know existed can render your
own computer unusable.”
Leslie Lamport

11. Build responsive
distributed systems
Reactive
Systems
Elasticity,
Resilience,
Messages
REACTIVE == BUILD BETTER SYSTEMS
Build concurrent
applications
Reactive
programming
Non-Blocking IO

12. MESSAGES

13. What’s wrong with HTTP?

14. HTTP => STRONG COUPLING

15. HTTP => UPTIME COUPLING

16. CB
CB
CB
CB
CB
CB
THE RISE OF CIRCUIT BREAKERS

17. Non-Blocking
Message Passing
Elasticity
Resilience
THE BENEFITS OF MESSAGING
Virtual
Addresses

18. APPLYING REACTIVE TO DISTRIBUTED SYSTEMS
RESPONSIVE
ASYNC MESSAGE
PASSING
ELASTICITY RESILIENCE

19. APPLYING REACTIVE TO DISTRIBUTED SYSTEMS
RESPONSIVE
ASYNC MESSAGE
PASSING
ELASTICITY RESILIENCE
Asynchronous
Non-Blocking
Message Passing

20. Reactive != multi-thread
Reactive == never-block

21. 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

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

23. Let’s look at
pragmatic
questions

24. What about
CompletionStage ?

25. What about
CompletionStage ?
Uni

26. @GET
@Produces(MediaType.TEXT_PLAIN)
@Path("/greeting/{name}")
public Uni<String> greeting(@PathParam String name) {
return service.greeting(name);
}
Using Unis in JAX-RS resources / Rest Client
@GET
@Path("/name/{name}")
@Produces("application/json")
Uni<Country> getByName(@PathParam String name);

27. What about streams?

28. CompletionStage vs. Publisher
Publisher (Flow)
0..n items
Completion Stage
Eager
0..1 items
Lazy
Back-Pressure
Has operators No Operators

29. Mutiny: Uni and Multi
Multi
0..n items
Uni
Lazy (subscription)
1 item
Lazy (subscription + request)
Back-Pressure
Operators Operators

30. Back-Pressure 101
https://twitter.com/impurepics/status/1000466142866149377

31. JAX-RS returning Multi
@Produces(MediaType.APPLICATION_JSON)
@Path("/greeting/{count}/{name}")
public Multi<String> greetings(@PathParam int count, @PathParam String name) {
return service.greetings(count, name);
}
@Produces(MediaType.SERVER_SENT_EVENTS)
@SseElementType(MediaType.TEXT_PLAIN)
@Path("/stream/{count}/{name}")
public Multi<String> greetings(@PathParam String name) {
return service.infiniteGreetings(name);
}

32. I heard a lot about Kafka.
Does Kafka make me reactive?

33. Messaging / Streaming
Quarkus
Application Code
Container Host / Operating System
HTTP Messaging
Quarkus
Application Code
Container Host / Operating System Messaging
Middleware
HTTP, MESSAGING, STREAMING

34. Coffee Shop Barista Coffee Shop Barista
HTTP
Dashboard
REACTIVE COFFEE SHOP
https://github.com/cescoffier/quarkus-coffeeshop-demo
Orders, Queue
* Also applies to AMQP and other messaging protocols but we want to be “cool”
*

35. Bridge imperative -> reactive
DROP HTTP, SEND MESSAGES
@Inject @Channel("orders")
Emitter<Order> orders;
@Inject @Channel("queue")
Emitter<Beverage> states;
@POST @Path("/messaging")
public Order messaging(Order order) {
order.setOrderId(getId());
states.send(Beverage.queued(order));
orders.send(order);
return order;
}
Send to the
channel “orders”

36. @Incoming("orders")
@Outgoing("queue")
public Uni<Beverage> process(Order order) {
return Uni.createFrom(() -> {
Beverage coffee = prepare(order);
return coffee;
});
}
Process data
asynchronously*
* Many other options available to produce, process or consume data
Read from “orders”
Write to “queue”
PROCESSING MESSAGES

37. 37
@Inject
@Channel("beverages")
Multi<String> queue;
@GET
@Produces(MediaType.SERVER_SENT_EVENTS)
public Multi<String> getQueue() {
return queue;
}
Inject the data from the
channel “beverages”
Returns a stream
PUSHING DATA TO SSE

38. Is it a Reactive System?

39. Coffee Shop
Barista
Dashboard
Queue
Orders
BARISTAS TAKE BREAKS

40. Coffee Shop
Baristas
Queue
Orders
RUSH HOUR!
Dashboard

41. APPLYING REACTIVE TO DISTRIBUTED SYSTEMS
RESPONSIVE
ASYNC MESSAGE
PASSING
ELASTICITY RESILIENCE

42. Messaging / Streaming
Quarkus
Application Code
Container Host / Operating System
Reactive
HTTP Server
Messaging
Quarkus
Application Code
Container Host / Operating System Messaging
Middleware
BUT WHAT ABOUT REACTIVE STREAMS?
Reactive
Streams

43. CONCLUSION

44. Developer Joy Supersonic Subatomic Java
Unifies
imperative and reactive
Best of breed
libraries and standards
QUARKUS

45. QUARKUS = (REACTIVE + IMPERATIVE) / REACTIVE
Eclipse Vert.x / Netty
Undertow
(Servlet)
RESTEasy
(JAX-RS)
Reactive
Routes
Reactive
Messaging
Reactive
Data Access
Events
HTTP
Messages

46. 46
https://quarkus.io
@quarkusio
https://quarkusio.zulipchat.com