Async and evented programming with Netty and Scala

In company (OfficeDrop) presentation about how to address the problems of highly scalable systems.

Transcript

1. Scalable async and evented programming with Netty and Scala Maurício Linhares
2. How? The Java NIO package was added on Java 1.4, ten years ago. It has been upgraded now on Java 7 with a new filesystem API.
3. Why? !   Java needed a bare bones low level solution for IO operations; !   Direct to native buffers for IO operations that do not require any kind of CPU interaction to be copied over; !   Asynchronous model, so you don’t have to waste thread time sleeping;
4. But why? !   Synchronous IO operations are expensive and take time to finish; !   Copying memory bounded buffers from one place to the other is a definite way to kill the Garbage Collector; !   Every single thread waiting for an IO operation counts for the thread scheduler, consumes memory and stack resources;
5. Sync IO is not scalable !   Clients are not always talking to servers, most of their time they are just idle; !   Having one thread per client means this thread is parked most of the time, but still consuming resources; !   If you have thousands of clients, having thousands of threads is not an option in commodity hardware (and not even in specialized hardware);
6. What you need is async ! Fixed amount of threads (per CPU thread) waiting for events to happen; ! Everyone consumes work from a (possibly bounded) queue ; ! There is time wasted in sleep calls, everyone is CPU bound as much as possible;
7. High level example – Websockets with Jetty Project done last year with @rcarvalho
8. What if I need more control? !   The NIO library is rather complicated to handle directly for socket servers; ! Most socket servers run in a request-response cycle with a specific message format; ! And then we have NIO frameworks to do our job;
9. Netty comes to the rescue ! Direct child of the venerable Mina library; !   Builds upon the concepts defined by Mina, you have encoders, decoders, an execution model and the handler that receives messages; ! Hides most of the complexity of building a NIO client/ server from your code, you only have to care about receiving messages and working with them;
10. The channel pipeline Decoder Encoder Execution Model Messaging handler
11. Low level example PostgreSQL async driver