Akita HTTP Archive (HAR) logger for Rack/Rails applications

This provides Rack middleware and a Rails ActionController filter for logging HTTP request–response pairs to a HAR file.

Installation

Add this line to your application's Gemfile:

gem 'akita-har_logger'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install akita-har_logger

Usage

There are two options for instrumenting your Rack/Rails application. The first is to use the HAR logger as Rack middleware. The second is to use it as a Rails ActionController filter.

Depending on the framework you're using, one or both options may be available to you. If you are interested in logging RSpec tests, the filter option will capture traffic for both controller and request specs, whereas the middleware option only captures request specs.

Once your application is instrumented, when you run the application, HTTP requests and responses will be logged to the HAR file that you've specified. You can then upload this HAR file to Akita for analysis.

Middleware

To instrument with middleware, add Akita::HarLogger::Middleware to the top of your middleware stack. For convenience, you can call Akita::HarLogger.instrument to do this. We recommend adding this call to the bottom of config/environments/test.rb to add the middleware just to your test environment.

Here is a sample configuration for a test environment that just adds the instrumentation.

# config/environments/test.rb

Rails.application.configure.do
  # Other configuration for the Rails application...

  # Put the HAR logger at the top of the middleware stack, and optionally
  # give an output HAR file to save your trace. If not specified, this defaults
  # to `akita_trace_{timestamp}.har`.
  Akita::HarLogger.instrument(config, "akita_trace.har")
end

ActionController filter

To instrument with a filter, add an instance of Akita::HarLogger::Filter as an around_action filter to your ActionController implementation.

For convenience, you can call Akita::HarLogger::Filter.install to do this for all ActionControllers in your application. We recommend adding this call to a configuration initializer. For example, this initializer adds the filter only in the test environment:

# config/initializers/har_logging.rb

# Add the HAR logger as an `around_action` filter to all `ActionControllers`
# that are loaded by the application in the test environment. Optionally give
# an output HAR file to save your trace. If not specified, this defaults to
# `akita_trace_{timestamp}.har`.
Akita::HarLogger::Filter.install("akita_trace.har") if Rails.env.test?

You can also selectively instrument your ActionController implementations by adding the filter manually. Here is a bare-bones ActionController implementation that adds the filter only in the test environment.

# app/controllers/application_controller.rb

class ApplicationController < ActionController::API
  include Response
  include ExceptionHandler

  # Add the HAR logger as an `around_action` filter. Optionally give an output
  # HAR file to save your trace. If not specified, this defaults to
  # `akita_trace_{timestamp}.har`.
  around_action Akita::HarLogger::Filter.new("akita_trace.har") if Rails.env.test?
end

Development

After checking out the repo, run bin/setup to install dependencies. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Implementation notes

References used when building this:

• https://ieftimov.com/post/writing-rails-middleware/
• https://github.com/rack/rack/blob/master/SPEC.rdoc
• https://w3c.github.io/web-performance/specs/HAR/Overview.html
• http://www.softwareishard.com/blog/har-12-spec/