Structured, key-value logging for your rack apps. Inspired by lograge.

Application logs are an incredibly rich source of information. But digging out the information can be extremely painful if your logs are not structured in an easily parsable manner.

Rack::KeyValueLogger logs key-value pairs, where the key and value are separated by a "=" character. Pairs are separated by pipe ("|") characters. Here's an example of what a log line looks like:

ts=2013-04-26T01:14:36Z|method=GET|url=/homepage|params=page=2|user_id=123|scheme=http|user_agent=curl/7.24.0 (x86_64-apple-darwin12.0) libcurl/7.24.0 OpenSSL/0.9.8r zlib/1.2.5|remote_ip=127.0.0.1|http_version=HTTP/1.1|requested_content_type=text/html|log_source=key_value_logger|status=200|content-length=111|content_type=text/html|runtime=21.553

gem 'rack-key_value_logger'

class MyApp < Sinatra::Base
  use Rack::KeyValueLogger
end

module MyApp
  class Application < Rails::Application
    # ...
    config.middleware.use "Rack::KeyValueLogger"
  end
end

A number of configuration options are supported when adding Rack::KeyValueLogger to the middleware stack.

• :log_failure_response_bodies - true or false. Logs the entire response body to the response_body key on 40x responses. Defaults to false.
• :ignore_paths - A regular expression of paths we should not log.
• :logger - A Logger instance. Defaults to Logger($stdout).
• :user_id - A string key at which the current user's id is stored in env["rack.session"]. Defaults to "user_id".