Ratpack is a set of libraries for writing fast, efficient, evolvable and well tested HTTP applications written in Java 8 or any alternative JVM language that plays well with Java, such as Groovy. The session will start with an introduction about Ratpack, and what makes it different from other popular frameworks like Grails or Vert.x, to name a few. Then, it will cover the fundamentals of the async programming model used in Ratpack applications, as well as other core concepts like handlers and the registry. Also, some of of the core modules ("plug-ins") will be described. Finally, it will cover how to test Ratpack applications using Groovy and Spock.

1. @alvaro_sanchez@alvaro_sanchez
Ratpack 101
Álvaro Sánchez-Mariscal
Web Architect - odobo

2. @alvaro_sanchez
About me
● Passionate Software Developer.
○ Former BEA/Sun instructor, Groovy fanboy since 2006.
● Speaker at Codemotion, JavaLand, GeeCON,
Spring IO, GR8Conf, GGX and Greach.
● Author of several Grails plugins.
● Working now at as a Web Architect.

3. @alvaro_sanchez
About
● HTML5 platform for gambling games.
● We provide game developers a Javascript SDK.
● Server side logic and maths are handled by our
industry certified game engines.
● Seamless integration with several casinos.
● Check out play.odobo.com and play for free!

4. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

5. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

6. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

7. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

8. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

9. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

10. @alvaro_sanchez
Slides, code and workshop available
● Slides:
○ http://www.slideshare.net/alvarosanchezmariscal/
● Companion code:
○ https://github.com/alvarosanchez/ratpack-101-talk
● Workshop:
○ https://github.com/alvarosanchez/ratpack-101

11. @alvaro_sanchez
Before we start
● Raise your hand if you know:
○ Java.
○ Groovy.
○ Spock.
○ Ratpack?

12. @alvaro_sanchez
Introduction
● Ratpack is:
○ A set of Java 8 libraries…
○ … lightweight, un-opinionated, Netty-based...
○ … for writing non-blocking HTTP applications…
○ … focused on performance and efficiency…
○ … with an emphasis on testability..
○ … embracing Java 8 or Groovy as programming
languages.

13. @alvaro_sanchez
When to use Ratpack?
● For microservices.
● For high performance applications.
● For lightweight services (no container,
batteries included).

14. @alvaro_sanchez
Ratpack is developer friendly
● Startup in milliseconds.
● Development-time reloading with Spring
Loaded.
● First-class support for functional testing.

15. @alvaro_sanchez
Demo
1. Groovy script.
2. Gradle build with Lazybones.

16. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

17. @alvaro_sanchez
Handlers
● An incoming request is passed through the
handler chain.
● A handler can:
○ Respond to the request.
○ Delegate to the next handler in the chain.
○ Insert more handlers in the chain and delegate to
them.

18. @alvaro_sanchez
Handlers
● Each handler is given a Context instance.
○ To interact with the request / response objects.
○ To access the registry.
○ Etc.
● Note that Ratpack is not based on the Servlet
API.

19. @alvaro_sanchez
Demo
3. Handlers.

20. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

21. @alvaro_sanchez
The Context
● The Context provides:
○ Access to the HTTP Request and Response objects.
○ Interaction with other handlers through next() and
insert() methods.
○ Access to objects in the registry.

22. @alvaro_sanchez
The registry
● The context is also a Registry of objects.
● Handlers can store objects into the context for
use by downstream handlers.

23. @alvaro_sanchez
Demo
4. Working with the context.

24. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

25. @alvaro_sanchez
Ratpack modules
● Ratpack can integrate with Google Guice for:
○ Dependency injection for services, etc.
○ Officially supported modules.
○ Reusing your own components as your modules.

26. @alvaro_sanchez
Official modules (1/2)
● Benchmarks (JMH).
● Metrics.
● H2 Database.
● Handlebars.
● HikariCP JDBC pool.
● Hystrix.
● Jackson.
● New Relic.
● Pac4J.
● Reactor.
● Groovy Remote
Control.

27. @alvaro_sanchez
Official modules (2/2)
● RxJava.
● HTTP Sessions.
● Spring Boot.
● Thymeleaf.

28. @alvaro_sanchez
Demo
5. Using Guice and the Jackson module.

29. @alvaro_sanchez
Agenda
● Introduction.
● The handlers chain.
● The context.
● Ratpack modules.
● Asynchronous & Non Blocking model.
● Q&A.

30. @alvaro_sanchez
The classic approach
● A thread-per-request.
○ There is a relatively large thread pool.
○ Each request is assigned a thread from the pool.
○ If the request handling code performs blocking I/O, the
thread sleeps until the result is received.
● Overhead: thread management, memory
consumption.

31. @alvaro_sanchez
Ratpack’s value proposition
● HTTP IO is event-driven (non blocking).
○ Powered by Netty.
● Handler chain is organised as a pipeline of
asynchronous functions.
○ Small compute thread pool.
○ Blocking operations are executed in a separate pool.
○ Integration with existing libraries like RxJava.

32. @alvaro_sanchez
Async model
● Ratpack guarantees a deterministic flow.
○ Promises are executed in the order they are defined.
○ Once the promises are resolved, they are executed in
compute threads.
● Async functions can be composed.
○ To avoid the callback hell.

33. @alvaro_sanchez
Demo
6. Asynchronous model.

34. @alvaro_sanchez
Álvaro Sánchez-Mariscal
Web Architect - odobo
Images courtesy of
Dzięki!