101 different adapters for different log levels

Yell 101 - How To: Different Adapters for Different Log Levels

Using multiple adapters with different log levels utilized the full potential of what Yell can do for you.

A very common use case is to log notice messages into a general file, whereas exceptions and stack traces go to a designated error.log. The following example defines a Yell logger writing debug, info and warn messages into the 'application.log' and error and warn messages into the 'error.log'.

logger = Yell.new do |l|
  l.adapter :file, 'application.log', :level => (:debug..:warn)
  l.adapter :file, 'error.log', :level => :error
end

[ :debug, :info, :warn, :error, :fatal ].each do |level|
  logger.send level, "This is a #{level} message"
end

# === application.log ===
#=> This is a debug message
#=> This is a info message
#=> This is a warn message
# === error.log ===
#=> This is a error message
#=> This is a fatal message

You may combine adapters with levels as you like. For instance: one file for every level:

logger = Yell.new do |l|
  l.adapter :file, 'debug.log', :level => [:debug]
  l.adapter :file, 'info.log',  :level => [:info] 
  l.adapter :file, 'warn.log',  :level => [:warn]
  l.adapter :file, 'error.log', :level => [:error]
  l.adapter :file, 'fatal.log', :level => [:fatal]  
end

General Production Logger

Most times in a production environment, you don't care about :debug messages at all. Your logger is set to a minimum level of :info to begin with. Also, you want your error/critical messages to go into a separate error.log file. Also, since you don't want to end up with one big and bloated logfile and need to know roughly when something critical has been logged, you want a daily rollover of your logfiles. Here is an easy Example to achive that:

logger = Yell.new do |l|
  l.level = :info # will only pass :info and above to the adapters

  l.adapter :datefile, 'production.log', :level => Yell.level.lte(:warn)
  l.adapter :datefile, 'error.log', :level => Yell.level.gte(:error)
end