Anatomy of a Web Service, part 2 – “RedBarrel”
by Tarek Ziadé
I was talking about web services the other day: read it back as an introduction to this post.
I am pursuing this DSL experiment as I have now finished a working prototype of a micro-framework. I’ve called it RedBarrel (Monty reference). I’ve called the DSL files “RBR files”.
RedBarrel is a pure Python implementation of the DSL I’ve described in the previous post and does the following:
- loads the DSL file and run a WSGI web application (via rb-run)
- Allows you to check the syntax of an RBR file (via rb-check)
- generates a documentation page for the APIs at /__doc__ Note that description fields can be in reStructuredtext and are rendered in HTML
- publishes the DSL file at /__api__
- runs the code pointed in the DSL and does the post- and pre- processing as described
Here’s an example of a web service, that capitalizes the string you sent to it — and requires authentication and json input.
define path capitalize ( description "A web service with several post/pre processing", method POST, url /capitalize, use python:redbarrel.demos.capitalize, response-status ( describe 200 "Success", describe 400 "The request is probably malformed", describe 401 "Authentication failure" ), request-body ( description "Send a string in json and the server returns it Capitalized.", unless type is json return 400 ), request-headers ( unless Authorization validates with redbarrel.demos.auth return 401 ), response-headers ( set content-type "application/json" ), response-body ( description "The string, Capitalized !", unless type is json return 503 ) );
The one thing I am not entirely sure about yet, is if I want to provide helpers to instantiate some objects in memory when the server starts. That’s useful when you want to keep a DB connector open or simply avoid initializing many things on every request. But that’s very easy to implement with global variables… Maybe an “application context” could be created, for some functions to add objects inside.
Anyways, I’ve started to re-write a few web services to see how the DSL fits, and so far it looks useful: I have reduced a lot the boiler-plate code and the API is self-documented.
The code is still at Bitbucket and I am looking for some feedback or other people that are writing web services that want to experiment with it !