clogger - configurable request logging for Rack

clogger is Rack middleware for logging HTTP requests. The log format is customizable so you can specify exactly which fields to log.


  • highly customizable with easy-to-read nginx-like log format variables.

  • pre-defines Apache Common Log Format, Apache Combined Log Format and Rack::CommonLogger (as distributed by Rack 1.0 and 1.1) formats. See Clogger::Format for the predefined formats.

  • Untrusted values are escaped (all HTTP headers, request URI components) to make life easier for HTTP log parsers. The following bytes are escaped:

    ' (single quote)
    " (double quote)
    all bytes in the range of \x00-\x1F
  • multi-instance capable and (optionally) reentrant. You can use clogger in a multi-threaded server, and even multiple cloggers logging to different locations and different formats in the same process.

  • Pure Ruby version for non-MRI versions of Ruby (or via CLOGGER_PURE=1 in the environment). The optional C extension is loaded by default under C Ruby and under Rubinius, too.


clogger may be loaded as Rack middleware in your

# ENV['CLOGGER_PURE'] = '1' # uncomment to disable C extension
require "clogger"
use Clogger,
    :format => :Combined,
    :path => "/path/to/log",
    :reentrant => true

If you're using Rails 2.3.x or later, in your config/environment.rb somewhere inside the “ do |config|” block:

config.middleware.use 'Clogger',
    :format => :Combined,
    :path => "/path/to/log",
    :reentrant => false

Instead of specifying a :path, you may also specify a :logger object that receives a “<<” method:

use Clogger, :logger=> $stdout, :reentrant => true


  • $http_* - HTTP request headers (e.g. $http_user_agent)

  • $sent_http_* - HTTP response headers (e.g. $sent_http_content_length)

  • $content_length - HTTP request body size ($http_content_length is not allowed by Rack)

  • $content_type - HTTP request content type ($http_content_type is not allowed by Rack)

  • $cookie_* - HTTP request cookie (e.g. $cookie_session_id) Rack::Request#cookies must have been used by the underlying application to parse the cookies into a hash.

  • $request_method - the HTTP request method (e.g. GET, POST, HEAD, …)

  • $path_info - path component requested (e.g. /index.html)

  • $query_string - request query string (not including leading “?”)

  • $request_uri - the URI requested ($path_info?$query_string)

  • $request - the first line of the HTTP request ($request_method $request_uri $http_version)

  • $request_time, $request_timePRECISION - time taken for request (including response body iteration). PRECISION defaults to 3 (milliseconds) if not specified but may be specified anywhere from 0(seconds) to 6(microseconds).

  • $time_iso8601 - current local time in ISO 8601 format, e.g. “1970-01-01T00:00:00+00:00”

  • $time_local - current local time in Apache log format, e.g. “01/Jan/1970:00:00:00 +0000”

  • $usec - current time in seconds.microseconds since the Epoch

  • $msec - current time in seconds.milliseconds since the Epoch

  • $body_bytes_sent - bytes in the response body (Apache: %B)

  • $response_length - body_bytes_sent, except “-” instead of “0” (Apache: %b)

  • $remote_user - HTTP-authenticated user

  • $remote_addr - IP of the requesting client socket

  • $status - three-digit HTTP status code (e.g. 200, 404, 302)

  • $ip - X-Forwarded-For request header if available, $remote_addr if not

  • $pid - process ID of the current process

  • $eThread.current - Thread processing the request

  • $eActor.current - Actor processing the request (Revactor or Rubinius)

  • $envvariable_name - any Rack environment variable (e.g. rack.url_scheme)



The latest development happens in git and is published to the following:

git clone git://
git clone git://

You may also browse and download snapshot tarballs:

The mailing list (see below) is central for coordination and development. Patches should always be sent inline (git format-patch -M + git send-email) so we can reply to them inline.


All feedback (bug reports, user/development discussion, patches, pull requests) go to the public mailing list.

Do not send HTML mail or attachments. Do not top post.



For RubyGems users:

gem install clogger

There is an optional C extension that should be compatible with MatzRuby. The extensions should automatically be disabled for users of other Ruby implementations, but be sure to let us know if that's not the case.