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Modern app programming with RxJava and Eclipse Vert.x

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Thomas Segismont

With the advent of mobile web and IoT (Internet of Things), today's applications need to handle a lot of concurrent requests while staying responsive and easy to scale. Infrastructure plays a role in achieving these goals, but changing your programming style can help too. In this presentation, we will make the case for reactive programming, and introduce RxJava in particular. Then we will guide you through the process of building a real-life web application, based on Vert.x 3 and RxJava, communicating with databases, external services and modern datastores. You will learn how Vert.x integrates with RxJava, and why its simplicity makes it a perfect runtime for reactive applications.

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Modern app programming with RxJava & Eclipse Vert.x
Who am I? ● Thomas Segismont ● tsegismont on GitHub, Twitter, Gmail, Freenode... ● Vert.x core team since August 2016 ● At Red Hat since November 2012 (RHQ and Hawkular) #RivieraDev @vertx_project
Expectations ● Goals – Why is reactive programming important? – What are RxJava and Vert.x? – How can I combine them to build scalable, efficient and resilient apps? ● Non goals – In-depth study of RxJava or Vert.x #RivieraDev @vertx_project
Back to the late 90s… A hotel room booking engine
http://example.com http://example.com http://example.com
Such apps are mainstream today! ● Microservices ● API economy #RivieraDev @vertx_project
Alexandre Duret-Lutz (CC BY-SA 2.0)
Event loop systems
Reactor pattern Single thread
New stuff? ● Browser (AJAX, #setTimeout) ● GUI ● Node.js #RivieraDev @vertx_project
Event loop benefits ● Simple concurrency model ● Mechanical sympathy http://bit.ly/2cJMBsG – Higher throughput – Predictable latency #RivieraDev @vertx_project
Vert.x
What is Vert.x ● A toolkit (lib) ● … to build polyglot (on the JVM) – JS, Groovy, Ruby, Scala (3.4), Kotlin (3.4) ● … reactive systems #RivieraDev @vertx_project
Demo Damn simple verticle
Modern app programming with RxJava and Eclipse Vert.x
Multi-Reactor #RivieraDev @vertx_project
Event Bus ● Nervous system of Vert.x ● Message passing style ● Different messaging paradigms: – Point to point – Publish/Subscribe – Request/Reply #RivieraDev @vertx_project
Running blocking code ● In the real world, most JVM libraries have blocking APIs – JDBC – io.File – Your legacy libs ● With Vert.x you can interact with blocking parts easily ● You won’t throw away your code assets! #RivieraDev @vertx_project
Modern app programming with RxJava and Eclipse Vert.x
Callback based (reactive imperative)
CALLBACK HELL !
RxJava
Data and events flows ● It is great at organizing transformation of data and coordination of events ● It makes most sense when many sources of events are involved (modern apps!) #RivieraDev @vertx_project
Push based Observable Observer Subscription ● OnNext 0..∞ ● Terminal event 0..1 – OnComplete – OnError #RivieraDev @vertx_project
Reactive pull backpressure Observable Observer Subscription Request #RivieraDev @vertx_project
Observable / Single / Completable Zero One Many Sync void T Iterable<T> Async Completable Single<T> Observable<T> #RivieraDev @vertx_project
Demo Damn simple Rx Verticle
Music Store Demo https://github.com/tsegismont/vertx-musicstore
http://example.com http://example.com http://example.com https://coverartarchive.org/ Postgres Couchbase Vert.x RxJava Vert.x Web Client HTTP Vert.x JDBC Client Couchbase RxJava driver Event Bus Bridge (WebSocket) Vert.x Local Cache
Observable#map ReactiveX.io Creative Commons Attribution 3.0 License
Observable#map private Single<JsonArray> findAlbums(SQLConnection sqlConnection, Long artistId) { return sqlConnection.rxQueryStreamWithParams(findAlbumsByArtist, new JsonArray().add(artistId)) .flatMapObservable(SQLRowStream::toObservable) .map(row -> new JsonObject().put("id", row.getLong(0)).put("title", row.getString(1))) .collect(JsonArray::new, JsonArray::add) .toSingle(); } #RivieraDev @vertx_project
Observable#flatMap ReactiveX.io Creative Commons Attribution 3.0 License
Single#flatMap public void handle(RoutingContext rc) { dbClient.rxGetConnection().flatMap(sqlConnection -> { return findGenres(sqlConnection).doAfterTerminate(sqlConnection::close); }).flatMap(genres -> { rc.put("genres", genres); return templateEngine.rxRender(rc, "templates/index"); }).subscribe(rc.response()::end, rc::fail); } #RivieraDev @vertx_project
Single#zip ReactiveX.io Creative Commons Attribution 3.0 License
Single#zip Single<JsonObject> as = findAlbum(sqlConnection, albumId); Single<JsonArray> ts = findTracks(sqlConnection, albumId); return Single.zip(as, ts, (album, tracks) -> { Map<String, Object> data = new HashMap<>(2); data.put("album", album); data.put("tracks", tracks); return data; }).doAfterTerminate(sqlConnection::close); #RivieraDev @vertx_project
Observable#observeOn ReactiveX.io Creative Commons Attribution 3.0 License
Observable#observeOn #RivieraDev @vertx_project albumCommentsBucket.query(Query.parametrized(findRecentCommentsByAlbum, params)) .observeOn(RxHelper.scheduler(rc.vertx())) .flatMap(AsyncQueryResult::rows) .limit(5) .collect(JsonArray::new, (jsonArray, row) -> jsonArray.add(new JsonObject(row.value().toMap()))) .toSingle() .flatMap(data -> { rc.put("comments", data); return templateEngine.rxRender(rc, "templates/partials/album_comments"); }).subscribe(rc.response()::end, rc::fail);
#RivieraDev @vertx_project http://red.ht/2pgMEoA
Thank you! http://vertx.io Come get your sticker! #RivieraDev @vertx_project

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