!1 Dreaming of Streaming with Reactive Programming Edson Yanaga, Red Hat @yanaga 

!2 A stack to write Java apps Cloud Native Microservices Serverless 

!3 Developer Joy Quarkus Benefits Supersonic Subatomic Java Unifies imperative and reactive Best of breed libraries and standards 

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 

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. ... 

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 

Events Messages Failures Is Reactive == Event-Driven ? 

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

FROM EVENT-DRIVEN TO SYSTEMS 

Build responsive distributed systems Reactive Systems Elasticity, Resilience, Messages Build concurrent applications Reactive programming Reactive streams Non-Blocking Asynchronous TWO SIDES OF THE SAME COIN 

REACTIVE => RESPONSIVE 

Asynchronous Message Passing REACTIVE => RESPONSIVE 

Async != multi-thread Async == never-block 

FROM HTTP 
 TO MESSAGING 

HTTP => STRONG COUPLING 

HTTP => UPTIME COUPLING 

CB CB CB CB CB CB THE RISE OF CIRCUIT BREAKERS 

Non-Blocking Message Passing Elasticity Resilience THE BENEFITS OF MESSAGING 

Message Stream Publish/ Subscribe Request-Reply DATA AT REST => DATA IN MOTION 

Supersonic. Subatomic. REACTIVE. 

Messaging / Streaming Quarkus Application Code Container Host / Operating System Async HTTP Messaging Quarkus Application Code Container Host / Operating System Messaging Middleware QUARKUS = {HTTP, MESSAGING, STREAMING} 

MicroProfile Reactive Messaging Quarkus Application Code Container Host / Operating System Async HTTP Messaging Quarkus Application Code Container Host / Operating System Messaging Middleware QUARKUS = {HTTP, MESSAGING, STREAMING} 

Coffee Shop Barista Coffee Shop Barista HTTP Board Kafka REACTIVE COFFEE SHOP https://github.com/cescoffier/quarkus-coffeeshop-demo Orders, Queue 

Coffee Shop Barista HTTP WHAT’S THE PROBLEM WITH SYNCHRONOUS On a peak of load ● Concurrency limited by the coffee shop thread pool ● Must scale up the number of baristas ● Require some kind of load-balancer ● COLD COFFEE or NO COFFEE On failing barista ● Orders are lost ● NO COFFEE On slow barista ● Coffee Shop gets slow ● COLD COFFEE 

@POST @Path("/http") public Beverage order(Order order) { return client.order(order); } @POST @Path("/async") public CompletionStage order(Order order) { return client.orderAsync(order); } FROM SYNC TO ASYNC HTTP Non-Blocking Thread released @POST @Produces("application/json") @Consumes("application/json") Beverage order(Order order); @POST @Produces("application/json") @Consumes("application/json") CompletionStage orderAsync(Order order); 

Coffee Shop Barista DEMO HTTP 

Bridge imperative -> reactive DROP HTTP, SEND MESSAGES @Inject @Stream("orders") Emitter orders; public Order enqueue(Order order) { order.setOrderId(UUID.randomUUID().toString()); orders.send(jsonb.toJson(order)); return order; } Send “data” to the channel “orders” 

@Incoming("orders") @Outgoing("queue") public CompletionStage prepare(String message) { Order order = fromJson(message, Order.class); return makeIt(order) .thenApply(beverage -> PreparationState.ready(order, beverage) ); } Process data async* * Many other options available to produce, process or consume data Read from “orders” Write to “queue” PROCESSING MESSAGES 

Coffee Shop Barista Board Queue Orders PROGRESS 

@Inject @Stream("beverages") Publisher queue; @GET @Produces(MediaType.SERVER_SENT_EVENTS) public Publisher getQueue() { return queue; } Inject a stream Returns a stream PUSHING DATA TO SSE 

Coffee Shop Barista Board Queue Orders DEMO 

mp.messaging.smallrye-kafka.bootstrap.servers=localhost:9092 mp.messaging.smallrye-kafka.key.serializer=...StringSerializer mp.messaging.smallrye-kafka.value.serializer=...StringSerializer mp.messaging.outgoing.queue.connector=smallrye-kafka mp.messaging.outgoing.queue.acks=1 Direction MAPPING CHANNELS TO KAFKA TOPICS Channel Name 
 (= topic if not set) 

Coffee Shop Barista Board Queue Orders BARISTAS TAKE BREAKS 

Coffee Shop Baristas (Julie and Tom) Queue Orders RUSH HOUR! Board 

SUMMARY 

HTTP, Messaging, Streaming Quarkus Non-Blocking IO QUARKUS = {HTTP, MESSAGING, STREAMING} 

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

BRIDGE REACTIVE AND IMPERATIVE @Stream(“foo”) Emitter @Incoming(“foo”) @Outgoing(“bar”) @Stream(“bar”) Publisher @Outoing(“foo”) @Incoming(“bar”) Publisher Processor Subscriber Connector Connector 

Non-Blocking Message Passing Elasticity Resilience REACTIVE SYSTEMS MADE EASY 

Quark us Imperativ e Reactive CRUD, REST, CLI... Reactiv e System s Data Streamin g Supersonic, Subatomic, REACTIVE 

!41 Thank you.