Development with Vert.x: an event-driven application framework for the JVM

Development with Vert.x:an event-driven application

framework for the JVMDavid Wu@wuman

blog.wu-man.com

Taiwan Java User Group (2013/06/29)

1Monday, July 1, 13

about.me/wuman2Monday, July 1, 13

What is Vert.x?

3Monday, July 1, 13

What most people will tell you about Vert.x

• A general-purpose application framework running on JVM

• Performant: asynchronous APIs, event-driven, non-blocking, etc.

• Highly scalable but also easy to implement concurrency

• Polyglot: intermix Java, JS, Ruby, Groovy, Python, etc.

4Monday, July 1, 13

What I think about Vert.x

• All-in-one framework that allows you to focus on your application rather than fiddling with different technologies

• Business friendly Apache License 2.0

• Loose coupling modules that interoperate in a system

5Monday, July 1, 13

Background on the C10K Problem

6Monday, July 1, 13

Shift from Threading to Asynchronous

the story of switching from Apache to Node.js

7Monday, July 1, 13

The inevitable comparison to Node.js

• A single event loop serving a high volume of connections via an asynchronous programming model

• Most of the real work are done in a pool of background threads

8Monday, July 1, 13

Asynchronous Programming Model

vertx.createHttpServer().requestHandler( new Handler<HttpServerRequest>() { public void handle(HttpServerRequest request) { log.info("A request has arrived on the server!"); request.response().end(); } }).listen(8080, "localhost");

9Monday, July 1, 13

But there are 3 problems with Node.js

10Monday, July 1, 13

Problems with Node.js

• Well, it’s not Java (and this is a Java User Group)

• Does not easily scale both vertically and horizontally

• Single event loop fails when you have CPU-intensive tasks or 3rd-party blocking APIs


Vert.x to the rescue

• Use all available cores on a single machine

• Horizontally scale out to multiple boxes

• Allow blocking calls to NOT run on an event loop


Introduction to Vert.x instance and Verticles

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Vert

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Vert.x instance


Verticles are extremely isolated

• Verticles are isolated with separate class loaders

• A verticle never gets executed by more than one thread concurrently

• No race conditions, no deadlocks. You write your code as single threaded.


What about communication?


Message Passing via the Event Bus

Vert

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Vert

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Vert

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Vert

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Vert.x instance


Very Powerful Event Bus

Vert

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Vert

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Vert

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Vert

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Registering a Message Handler

EventBus eb = vertx.eventBus();

Handler<Message> myHandler = new Handler<Message>() { public void handle(Message message) { System.out.println("I received a message " + message.body); }};

eb.registerHandler("test.address", myHandler);


Message Types

• Primitives and their boxed types

• String

• org.vertx.java.core.json.JsonObject

• org.vertx.java.core.json.JsonArray

• org.vertx.java.core.buffer.Buffer


Pub/Sub Model

eb.publish("test.address", "hello world");


Point-to-Point Model

eb.send("test.address", "This is a message", new Handler<Message<String>>() { public void handle(Message<String> message) { System.out.println("I received a reply " + message.body); } });

EventBus eb = vertx.eventBus();

Handler<Message> myHandler = new Handler<Message>() { public void handle(Message message) { System.out.println("I received a message " + message.body); message.reply("This is a reply"); }};

eb.registerHandler("test.address", myHandler);


Shared Maps and Sets

ConcurrentMap<String, Integer> map = vertx.sharedData().getMap("demo.mymap");

map.put("some-key", 123);

Set<String> set = vertx.sharedData().getSet("demo.myset");

set.add("some-value");


Module System


Writing Verticles

import org.vertx.java.core.Handler;import org.vertx.java.core.net.NetSocket;import org.vertx.java.core.streams.Pump;import org.vertx.java.platform.Verticle;

public class Server extends Verticle {

public void start() { vertx.createNetServer().connectHandler(new Handler<NetSocket>() { public void handle(final NetSocket socket) { Pump.createPump(socket, socket).start(); } }).listen(1234); }}

vertx run Server.java


Deploying Verticles programmatically

// For example - deploy some other verticle container.deployVerticle("foo.js", new AsyncResultHandler<String>() { public void handle(AsyncResult<String> deployResult) { if (deployResult.succeeded()) { System.out.println(“Yay!”); } else { System.out.println(“Error: “ + deployResult.cause()); } } });


Modules

• Package verticles into re-usable modules

• Simply a zip file containing module definition, code, and resources

• Very similar to the module system in Node.js

• Modules can be “zip” artifacts released in Maven Central

• Vert.x web site maintains a listing of Vert.x modules


Example Modules

• JDBC, Redis, MongoDB Persistors

• AMQP

• Mailer

• Persistent work queue

• Authentication Manager

• Session Manager

• Web framework

• Language implementations


Programming Experience


Core APIs

• TCP/SSL servers and clients

• HTTP/HTTPS servers and clients

• WebSockets servers and clients

• SockJS

• EventBus

• Shared Maps and Sets

• Buffers

• Flow control

• Timers

• Files

• Configuration


Container API

• Deploying and undeploying verticles

• Deploying and undeploying modules

• Logging

• Retrieve verticle configuration


Easy development

• Gradle template

• Maven archetype and plugin

• IDE debugging and testing


What is it good for?


Applications

• Realtime analytics dashboard

• Big data queries and task coordination

• Polyglot integration


Some Pain Points


Real life caveats

• Content assist in IDEs don’t work for busmod APIs

• You often find yourself tracing errors in the busmods, which can be difficult because the stack trace stops at message passing

• People writing in other languages often get frustrated by not being able to use native extensions that they are already used to.

• Hell of anonymous inner class callbacks and no good Java flow control libraries

• Java7 only. Doesn’t work on Android.


Conclusion


“Using a bleeding-edge framework is exciting at first.

Not so much afterwards.”

David Wu


Make it better.Contribute.

http://vert-x.github.io/




Thank you


Q & A


Development with Vert.x: an event-driven application framework for the JVM

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