Simple Example with Spray, Akka, and Squeryl

The basic setup is from the valuable spray template. The example covers

REST-Services with Spray
an event-driven architecture based on Akka
persistence with squeryl
Testing with Specs2

Structure

The project layout is corresponding to the classic maven style directory structure. All source code is located in src/main/scala and src/test/scala, respectively.

The source code is organized in the following packages:

api: The rest service stuff, i.e. definition of routes, Json marshallers
core: the rest agnostic business logic: message objects, operations
domain: the domain model as case class(es)
database: Squeryl schema definition, database configuration

Basic data flow

a Request hits the defined routes in the webservice actor
the Request is converted to a message object
An intermediate Actor is created per request to handle the completion of the request (pre request pattern)
the Message object is passed to the business logic actor via the per request Actor
the business logic actor mainly triggers the database interaction
the resulting data is passed back to the per request actor which completes the request

Performance

Performance and stability are pretty hard achieve in this setup. First I implemented the ask pattern, but the system crashed under heavy load. That is not tolerable in any serious system. Fiddling with akka settings doesn't help (or I couln't figure out how to configure everything correctly).

Then I switched to the pre request pattern. That solved the performance and stability problems for me as the blocking part of the system is encapsulated in a separate Actor per request. The overall performance is quite good now. Reading access gets up to 2000 req/s on a i5, which is quite nice.

TODO

Testing is broken right now.

Building

The project is built using sbt. Use

sbt gen-idea

to create Idea project files.

License

The project is released under the MIT license.