I love Node.JS, but I like proper IDE support too. So, when I read this blog-post on M2HTTP by Matt Might, it sparked my interest.
The goal of this project is to create a Scala webserver that is meant for developers to start as a basis for programming their backend. It is not an attempt to recreate NodeJs in Scala, but I do strive for the same simplicity of NodeJs. Instead of the event-driven javascript, Scala has very good Actors which are the building blocks of MSquareHttpd.
The original design in M2HTTPD by Matt is based on coroutines, implemented using queues. MSquareHttpd uses Akka Actors to communicate messages. This maintains the non-blocking nature of each building-block, but hides the queues and adds an event-driven aspect.
As in coroutines, there are Producers and Consumers. A Producer holds a list of Consumers, to wich it sends messages, i.e. the subscriber pattern. A Consumer has a Receive function that is called to process a Message. Combining them yields a Transducer which both sends and receives.
Messages have type parameters, and all producers and consumers declare which types of messages they can receive. This way building-blocks are composeable while maintaining type safety. A producer can send messages in with the Send() function, that uses implicit conversion to create a Message[T] of an object of type T. It is strongly recommended to send Immutable objects, for more info see the documentation page on Akka and the Java Memory Model.