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

transcript

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

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Background on the C10K Problem

6Monday, July 1, 13

Shift from Threading to Asynchronous

the story of switching from Apache to Node.js

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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

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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");

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But there are 3 problems with Node.js

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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

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.x instance

Very Powerful Event Bus

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

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

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