A tool for evaluating web page optimization and performance a la YSlow, PageSpeed, etc.

There are many tools available, either online or as browser plug-ins, that will tell you whether or not your page/site conforms to best practices, but as far as I know, there aren't a ton of libraries or utilities that you could drop into an existing system in order to perform evaluations programmatically. This tool is intended to provide a framework for defining and executing a configurable set of rules that will gauge or grade probable end user experience based on critieria like HTTP request and response parameters, page structure, number and size of requested resources, etc.

The general method of evaluating a web page will involve two distinct processing steps: building the resource tree and evaluation.

The domain model for this tool is the DOM of the target web page. This is represented in the application as a tree of linked objects which store information about the requests and responses for the various resources comprising the page.

Rules within the framework evaluate the tree of resources in order to determine how well a page will conform to a given best practice. Based on this evaluation the Rule object will calculate a score out of a possible 100 points and assign a letter grade A-F. Most of the logic for evaluation is contained in the Rule class whereas concrete implementations will define how deductions from the maximum possible score should be calculated for a given resource tree by defining the #compute_deductions method.

Rulesets are defined using a simple Ruby DSL syntax and identify a set of rules that should be calculated for a resource tree as well as the relative numeric weights that should be given to each rule. For example:

RSlow.configure do
  ruleset :simple_ruleset do                         # creates a Ruleset
    rule :RequestCount,                              # creates a Rule
         title:             "Minimize HTTP requests",
         weight:            8,
         resources: {
           script:    { maximum_allowed: 3, deduction: 3 },
           css:       { maximum_allowed: 2, deduction: 4 },
           css_image: { maximum_allowed: 6, deduction: 3 }
         }
    rule :Gzip,                                      # creates another Rule
         title:             "Compress components with GZip",
         weight:            8,
         deduction:         11

Ruleset evaluations are returned as strings containing JSON-formatted text.

Try running the example program. At present, it implements and configures a simple ruleset with a few basic rules, but it demonstrates the basic flow described above and the method of configuration of rule and scoring parameters.

./examples/simple_test.rb < YOUR URL >

• Performance improvements - creating fewer objects, lazy tree node creation, only making HEAD requests for resources that won't be parsed
• Create a simple interactive command-line client
• Gem packaging
• More out-of-box rules

• Yahoo! YSlow
  • Best Practices for Speeding Up Your Web Site
  • YSlow User Guide
  • Ruleset Matrix
• Google Page Speed
  • Official Google Homepage