Rack::Logjam

Logs helpful HTTP information on Rack requests.

Installation

Add this line to your application's Gemfile:

gem 'rack-logjam'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack-logjam

Usage

Including the Middleware

Grape

Include the middleware in your API classes with the use statement

module AwesomeApp
  class ApiV1 < Grape::API
    use Rack::Logjam::Grape::Middleware
  end
end

Rails

Require the middleware in config/application.rb

config.middleware.use( 'Rack::Logjam::Middleware' )

Configuration

At a minimum one must specify the logger that rack-logjam will use.

Rack::Logjam.configure |c|
  c.logger = Rails.logger
end

Formatters

Rack::Logjam includes several default formatters that are registered by default: Array, FormUrlencoded, Json, TextPlain, and Xml. Formatters are registered and selected by mime-types. If a the mime-type of a response does not have a regostered formatter, it will output a message to the log in place of the body specifying the lack of formatter and mime-type.

Additionally, you can configure custom mime-types with formatters in the configuration file.

Rack::Logjam.configure |c|
  # register custom mime-types with inlcuded formatters
  c.register_formatter 'application/vnd.awesome-app-v1+x-www-form-urlencoded', :FormUrlencoded
  c.register_formatter 'application/vnd.awesome-app-v1+json', :Json                        
  c.register_formatter 'application/vnd.awesome-app-v1+text', :TextPlain                        
  c.register_formatter 'application/vnd.awesome-app-v1+xml', :Xml

  # register custom mime-type with custom formatter
  c.register_formatter 'application/vnd.awesome-app-v1+csv', AwesomeApp::LogFormatter::Csv 
end

Filters

Filters can fully fully redact or truncate data within data structures. Filters are registered and selected by mime-types. No filters are registered by default. However, Rack::Logjam includes a Json filter. The Json filter uses JsonPath to specify which attributes are filtered.

Additionally, you can configure custom mime-types with filters in the configuration file.

Rack::Logjam.configure |c|
  # configure a mime-type with the built in Json filter
  #   this filter will truncate all image_as_base64 attributes 
  #   at any level of nesting and redact the subject/date_of_birth
  c.register_filter 'application/vnd.ncite-vetting-v1+json', :Json, [
    ['$..image_as_base64', :truncate, 10],
    ['$.subject_attributes.date_of_birth', :redact]
  ]
end

Custom Formatters and Filters

Writing a Custom Formatter

A formatter is a simply a class that accepts content in an initializer and implements a #render method with no parameters. Folowing is an implementation of a CSV formatter.

module AwesomeApp
  module Formatter
    class Csv
      def initialize( content )
        @content = content
      end

      def render
        content
      end

    protected

      attr_reader :content
    end
  end
end

The formatter must also be registered with a mime-type.

c.register_formatter 'application/vnd.awesome-app-v1+csv', AwesomeApp::Formatter::Csv

Writing a Custom Filter

A filter is a simply a class that accepts content and filters in an initializer and implements a #render method with no parameters. Folowing is a naive implementation of a CSV filter.

require 'csv' 

module AwesomeApp
  module Filters
    class Csv
      def initialize( content, filters )
        @content = content
        @filters = filters
      end

      def render
        CSV.parse("some long bit of text",data,123-45-6789,data") do |row|
          filters.each do |column, action, length| 
            row[column] = send( action, row[column], length )
          end
        end
      end

    protected

      def redact( val, *args )
        (val.nil? || val.empty?) ?
          val :
          "[REDACTED]"
      end

      def truncate( val, length )
        (val.nil? || val.empty?) ?
          val :
          "#{val[0..length]}...[TRUNCATED]..."
      end

      attr_reader :content,
                  :filters
    end
  end
end

The filter must also be registered with a mime-type.

c.register_filter 'application/vnd.awesome-app-v1+xml', AwesomeApp::Filters::Csv, [
  [0, :truncate, 10],
  [2, :redact]
]