One of the benefits of switching your Rails app to use SysLog is taking advantage of your OS’s system-wide logging, as well as having finer grained control over how to process your log messages. For example, you can split the logs up based on Rails app, mongrel process, or even by app server if you’re using remote syslog.

We’ll use Eric Hodel’s SyslogLogger Ruby Logger drop-in to get our app talking to SysLog.

Firstly, we’ll chuck the SyslogLogger library into our Rails app’s vendor directory:

cd vendor
curl http://rubyforge.org/frs/download.php/20520/SyslogLogger-1.4.0.tgz -L | tar -zxvv

We then need to set it up in environment.rb (or a specific environment file such as production.rb). We need to add its lib directory to the load path and set it as the DEFAULT_RAILS_LOGGER:

# Use SysLogger rather than the default logger.
# 
# see http://seattlerb.rubyforge.org/SyslogLogger/
# for example /etc/syslog.conf setups
$:.unshift File.join(RAILS_ROOT, "vendor", "SyslogLogger-1.4.0", "lib")
require 'syslog_logger'
config.logger = RAILS_DEFAULT_LOGGER = SyslogLogger.new('my_rails_app')

To test it we’ll load up script/console and give it a whirl:

>> RAILS_DEFAULT_LOGGER.error "Hello my lil SysLog"

and check our log, /var/system.log in OSX’s case, to see the results :

Jun  6 16:30:11 tim my_rails_app[2923]: Hello my lil SysLog

woohoo!

...and now we’re using SysLog we can use Eric’s other tool, ProductionLogAnalyzer, to identify performance bottleknecks of our application. Geoffrey Grosenbach (aka topfunky) wrote a Hodel3000CompliantLogger if you want to use this tool without SysLog).

Read more about SysLog on your SysLog daemon’s man page (on OSX check out the man pages for syslog, syslogd and syslogd.conf).