Rack::CommonLogger forwards every request to the given app, and logs a line in the Apache common log format to the logger.

If logger is nil, CommonLogger will fall back rack.errors, which is an instance of Rack::NullLogger.

logger can be any class, including the standard library Logger, and is expected to have either write or +<<+ method, which accepts the CommonLogger::FORMAT. According to the SPEC, the error stream must also respond to puts (which takes a single argument that responds to to_s), and flush (which is called without arguments in order to make the error appear for sure)

FORMAT = %{%s - %s [%s] "%s %s%s %s" %d %s %0.4f\n}

Common Log Format: httpd.apache.org/docs/1.3/logs.html#common

lilith.local - - [07/Aug/2006 23:58:02 -0400] "GET / HTTP/1.1" 500 -

%{%s - %s [%s] "%s %s%s %s" %d %s\n} %
Class Public methods
new(app, logger=nil)
# File lib/rack/common_logger.rb, line 26
def initialize(app, logger=nil)
  @app = app
  @logger = logger
Instance Public methods
# File lib/rack/common_logger.rb, line 31
def call(env)
  began_at = Time.now
  status, header, body = @app.call(env)
  header = Utils::HeaderHash.new(header)
  body = BodyProxy.new(body) { log(env, status, header, began_at) }
  [status, header, body]