Alpine Configuration Framework Design

Alpine Configuration Framework

The Alpine Configuration Framework (ACF) is a mvc-style application for configuring an Alpine device. The primary focus is for a web interface - ACF's main goal is to be a light-weight MVC "webmin".

Why Haserl + Lua

Other competitors in the arena were Webmin, Ruby on Rails, PHP with templates.

A full webmin (Perl), RoR or PHP implementation each require several MB of installed code, and can have very slow startup times, especially when used in "cgi" mode. After evaluating many options, we found that Lua has the following advantages:

• It is small (typically ~200KB of compiled code)
• It compiles and runs much faster than PHP, Perl or Ruby
• It provides a "normal" scripting language with features similar to PHP, perl, java, awk, etc.

Haserl + Lua provides a 'good enough' toolset to build a full-featured web application.

Why ACF is MVC

The MVC design pattern is used to separate presentation information from control logic. By MVC we mean:

• Model - code that reads / writes a config file, starts / stops daemons, or does other work modifying the router.
• View - code that formats data for output
• Controller - code that glues the two together

Note the lack of words like: HTML, XML, OO, AJAX, etc. The purpose of ACF's MVC is simply to separate the configuration logic from the presentation of the output.

The flow of a single transaction is:

start -> execute requested function in controller, optionally reading/writing a file using functions in the model -> execute the view to format the output -> end

Every transaction follows this pattern. For ACF developers, the focus should be on getting a model that does a proper job of abstracting the config file into useable entities and then building a controller that presents useable "actions" based on the model. The presentation layer should be last on the priority list.

For good background information on what ACF attempts to do, please see Terence Parr's paper "Enforcing Strict Model-View Separation in Template Engines" at http://www.cs.usfcs.edu or the local copy of the pdf.

ACF Developer's Guides

1. mvc.lua reference - mvc.lua is the core of ACF
2. mvc.lua example - build a simple application
3. acf www-controller reference - ACF www application functions

1. ACF core principles (Things that are standard across the application)