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Cedar IO

Summary

This is a Java NIO-based implementation of the Reactor Pattern, which is an OOP pattern for handling asynchronous IO. I'm still actively (ish) working on this project. It's just for educational purposes, to see how the pattern works.

The Reactor Pattern was created by Douglas C. Shmidt from Washington University, St. Louis, MO. Here's a link to the paper describing the pattern.

The pattern allows for the implementation of event-driven architectures by demultiplexing incoming service requests to callbacks that you register with the dispatcher thread.

Packages

  • cedario: this is the main implementation of the framework
  • web-server-example: this is an example I'm working on that shows how to use the framework in the context of a web server.

Todos

  • Implement the InititationDispatcher.removeHandler method.
  • Rethink the data structures I'm using in InitiationDispatcher. Having to handle registerEventHandler accepting an eventHandler and eventType makes things a bit messy, and I think I'm going to run into problems when I go to implement the removeHandler function.
  • Flush out the web-server-example to be an actual Rest HTTP service.
  • Allow an EventHandler to be registered on multiple EventTypes.
  • Currently, the dispatcher executes and handles events as a single thread. Instead, the dispatcher should create a threadpool and submit jobs (EventHandler's handleEvent) to the thread pool.
  • Use log4j instead of print statements.

My general comments on the pattern

I've always been curious about how event loops are implemented, so this was a cool project to throw together. One thing about the pattern that feels a bit odd to me is the tight coupling in the EventHandle class of the Handle (a SelectableChannel in this case) with the handleEvent application code. Ideally, I think that the application callback handler should be independent of the handle that it is registered on wait on. I need to go read up on some OOP patterns to decide how I would reimplement that.

Installation

This is a maven project. You can build from the source code and install it locally.

  1. git clone https://github.com/RyanStan/CedarIO
  2. mvn install