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Services réactifs avec Vert.x et intégration avec Kotlin
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Julien Ponge
November 09, 2017
Programming
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Services réactifs avec Vert.x et intégration avec Kotlin
Lyon Meetup User Group, November 2017
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Transcript
Services réactifs avec Vert.x et intégration avec Kotlin Julien Ponge
— @jponge 2017/11/09 — Lyon Kotlin User Group
None
Julien Ponge Maitre de Conférences “Delegated consultant to Red Hat”
on Vert.x Eclipse Golo + extensive F/OSS background ! https://julien.ponge.org/ " @jponge # @jponge https://www.mixcloud.com/hclcast/
Outline ✓ Reactive? Vert.x? ✓ Vert.x core 101 ✓ Reactive
extensions with RxJava 2 ✓ Kotlin coroutines and Vert.x
Reactive? Vert.x?
None
Application
Software Messages Requests Metrics Availability
Reactive systems Reactive streams Reactive programming Reactive “Responding to stimuli”
Manifesto, Actor, Messages Resilience, Elasticity, Scalability, Asynchronous, non-blocking Data flow Back-pressure Non-blocking Data flow Events, Observable Spreadsheets Akka, Vert.x Akka Streams, RxJava, Reactor, Vert.x Reactor, Reactive Spring, RxJava, Vert.x
Eclipse Vert.x Open source project started in 2012 Eclipse /
Apache licensing A toolkit for building reactive applications for the JVM 7K ⋆ on & Built on top of ! https://vertx.io " @vertx_project
None
(demo) “Hello world in action”
Vert.x core — 101
Vert.x Concurrency Model
while (isRunning) { String line = bufferedReader.readLine(); switch (line.substring(0, 4))
{ case "ECHO": bufferedWriter.write(line); break // ... // other cases ( ...) // ... default: bufferedWriter.write("UNKW Unknown command"); } }
x 1000 = '
C1 “When you have a line of text, call C2”
Something else with no blocking call either C2
Events Thread Event Loop
2 event-loops per CPU core by default
Verticles ) ) ) public class SomeVerticle extends AbstractVerticle
{ @Override public void start() throws Exception { } @Override public void stop() throws Exception { } } class SomeVerticle : AbstractVerticle() { override fun start() { } override fun stop() { } } exports.vertxStart = function() { } exports.vertxStop = function() { }
) * Configuration ) ) Verticle Deploy Deploy
) Worker thread pool Blocking task + executeBlocking Result
Message passing on the event bus
) ) Http server verticle Database client verticle ?
) . ) Http server verticle Database client verticle
Event Bus / “Details for user 1234?” Send to “user.db”
) . ) Http server verticle Database client verticle
Event Bus / “Details for user 1234?” Send to “user.db” Consume from “user.db”
) . ) Http server verticle Database client verticle
Event Bus / . “Details for user 1234?” “{data}”
/ Asynchronous messaging “foo.bar”, “foo-bar”, “foo/bar”, … Point to point
(with possible response back) Publish / subscribe
/ Distributed across Vert.x nodes Hazelcast, Ignite, Infinispan, … TCP
bridge interface Go, Python, C, JavaScript, Swift, C#, … SockJS bridge Seamless frontend / backend messaging
EventBus eb = vertx.eventBus(); eb.consumer("ping-address", message -> { System.out.println("Received message:
" + message.body()); message.reply("pong!"); }); EventBus eb = vertx.eventBus(); vertx.setPeriodic(1000, v -> { eb.send("ping-address", "ping!", reply -> { if (reply.succeeded()) { System.out.println("Received reply " + reply.result().body()); } else { System.out.println("No reply"); } }); });
MessageConsumer<Buffer> consumer = eventBus.consumer(“boilervroom.audiostream"); consumer.bodyStream().handler(buffer -> { if (!response.writeQueueFull()) {
response.write(buffer); } }); Streams Backpressure, supports pausing / resuming / dropping
const eventBus = new EventBus("/eventbus") traktorIn.addListener("controlchange", 5, (event) => {
eventBus.publish("boilervroom.vu-meter", { type: "volume-level", value: event.value }) }) eventBus.publish("boilervroom.fromtraktor", { type: "filter", number: 1, value: (event.value !== 0) }) Event Bus
switch (message.headers().get("action")) { case "all-pages": fetchAllPages(message); break; case "get-page": fetchPage(message);
break; case "create-page": createPage(message); break; case "save-page": savePage(message); break; case "delete-page": deletePage(message); break; default: message.fail(ErrorCodes.BAD_ACTION.ordinal(), "Bad action: " + action); }
private void deletePage(Message<JsonObject> message) { dbClient.getConnection(car -> { if (car.succeeded())
{ SQLConnection connection = car.result(); JsonArray data = new JsonArray().add(message.body().getString("id")); connection.updateWithParams(sqlQueries.get(SqlQuery.DELETE_PAGE), data, res -> { connection.close(); if (res.succeeded()) { message.reply(new JsonObject().put("result", "ok")); } else { reportQueryError(message, res.cause()); } }); } else { reportQueryError(message, car.cause()); } }); }
switch (message.headers().get("action")) { case "all-pages": fetchAllPages(message); break; case "get-page": fetchPage(message);
break; case "create-page": createPage(message); break; case "save-page": savePage(message); break; case "delete-page": deletePage(message); break; default: message.fail(ErrorCodes.BAD_ACTION.ordinal(), "Bad action: " + action); } 0 If lots of actions…
@ProxyGen public interface WikiDatabaseService { // ( ...) @Fluent WikiDatabaseService
savePage(int id, String markdown, Handler<AsyncResult<Void >> resultHandler); @Fluent WikiDatabaseService deletePage(int id, Handler<AsyncResult<Void >> resultHandler); static WikiDatabaseService createProxy(Vertx vertx, String address) { return new WikiDatabaseServiceVertxEBProxy(vertx, address); } // ( ...) } Proxy + handler source code will be generated Parameters from a JSON document Handlers for replies Generated proxy
dbService = WikiDatabaseService.createProxy(vertx, "wikidb.queue"); private void pageDeletionHandler(RoutingContext context) { dbService.deletePage(Integer.valueOf(context.request().getParam("id")),
reply -> { if (reply.succeeded()) { context.response().setStatusCode(303); context.response().putHeader("Location", "/"); context.response().end(); } else { context.fail(reply.cause()); } }); }
Dealing with asynchronous events
foo.a(1, res1 -> { if (res1.succeeded()) { bar.b("abc", 1, res2
-> { if (res.succeeded()) { baz.c(res3 -> { dosomething(res1, res2, res3, res4 -> { // (...) }); }); } }); } }); “Callback hell”
Callbacks RxJava 1 + 2 Quasar (vertx-sync) Kotlin coroutines (core)
(codegen)
Reactive Programming with Vert.x and RxJava Kotlin
RxJava Data and events flows Organising transformation of data and
coordination of events Makes most sense with many sources of events
Push based subscribe ➊ ➋push Observer Observable
Iterable / Observable try { for (String item : it)
{ ➊ } ➌ } catch (Throwable e) { ➋ } observable.subscribe(item -> { ➊ // onNext }, error -> { ➋ // onError }, () -> { ➌ // onCompleted });
0 0..1 0..n Reactive Completable Maybe<T> Single<T> Observable<T> Flowable<T> Interactive
void T Iterable<T>
None
None
None
None
Rxified Handler<AsyncResult> void listen(int port, Handler<AsyncResult<HttpServer>> ar) Single<HttpServer> rxListen(int
port);
(demo) RxJava
Kotlin coroutines (and Vert.x)
Coroutines are computer-program components that generalise subroutines for non-preemptive multitasking,
by allowing multiple entry points for suspending and resuming execution at certain locations. “ ” — https://en.wikipedia.org/wiki/Coroutine
Suspending lambdas and functions (suspend keyword) Compiler work for suspending
functions (state machines…) Low-level library: kotlin.coroutines create / start / suspend / intrinsics sequence and iterator generators (think Python, Golo, etc) High-level library: kotlinx.coroutines core primitives (launch, async, select, delay, …) reactive, UI, CompletableFuture, etc Kotlin Coroutines
) Suspend ) Begin ) ) End Resume Coroutine life
cycle
Coroutines are confined to Vert.x event loop threads awaitResult<T> and
awaitEvent<T> Channels from/to Vert.x streams Integrates with the coroutine ecosystem Coroutines for Vert.x
(demo) Coroutines with and without Vert.x
Outro
Vert.x Awesome Vert.x Stack Vert.x Core
None
Unified end-to-end reactive model + ecosystem (not just APIs…) For
all kinds of distributed applications (even the small-scale ones) Flexible toolkit, not a framework (your needs, your call)
https: //youtu.be/ZkWsilpiSqw 1 Applications réactives avec Eclipse Vert.x 2 Building
Reactive Microservices in Java https: //goo.gl/ep6yB9 2 Guide to async programming with Vert.x for Java developers https: //goo.gl/AcWW3A 3 Kotlin Slack — #vertx