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
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
- 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 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 per 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.
Dates in the domain model are currently java.sql.Timestamps and not java.util.Dates. The problem is that Squeryl is mapping java.util.Dates to SQL Dates thus loosing the time portion. Unfortunately, json4s requires the time portion to serialize/deserialize java.util.Dates. Alternatively, one can change the database mapping.
The project is built using sbt. Use
sbt gen-idea
to create Idea project files.
The project is released under the MIT license.