Description

LoggerInterface provides a module which may be used to extend an Analogger Client interface, and provide a dual-mode interface, supporting both the analogger client api, and the logger api.

Description From logger.rb:

The Logger class provides a simple but sophisticated logging utility that anyone can use because it‘s included in the Ruby 1.8.x standard library.

The HOWTOs below give a code-based overview of Logger‘s usage, but the basic concept is as follows. You create a Logger object (output to a file or elsewhere), and use it to log messages. The messages will have varying levels (info, error, etc), reflecting their varying importance. The levels, and their meanings, are:

So each message has a level, and the Logger itself has a level, which acts as a filter, so you can control the amount of information emitted from the logger without having to remove actual messages.

For instance, in a production system, you may have your logger(s) set to INFO (or WARN if you don‘t want the log files growing large with repetitive information). When you are developing it, though, you probably want to know about the program‘s internal state, and would set them to DEBUG.

Example

A simple example demonstrates the above explanation:

  log = Swiftcore::Analogger::Client.new('logger_interface','127.0.0.1','47990')
  log.extend(Swiftcore::Analogger::Client::LoggerInterface)
  log.level = Logger::WARN

  log.debug("Created logger")
  log.info("Program started")
  log.warn("Nothing to do!")

  begin
    File.each_line(path) do |line|
      unless line =~ /^(\w+) = (.*)$/
        log.error("Line in wrong format: #{line}")
      end
    end
  rescue => err
    log.fatal("Caught exception; exiting")
    log.fatal(err)
  end

Because the Logger‘s level is set to WARN, only the warning, error, and fatal messages are recorded. The debug and info messages are silently discarded.

How to log a message

Notice the different methods (fatal, error, info) being used to log messages of various levels. Other methods in this family are warn and debug. add is used below to log a message of an arbitrary (perhaps dynamic) level.

1. Message in block.

     logger.fatal { "Argument 'foo' not given." }
   

2. Message as a string.

     logger.error "Argument #{ @foo } mismatch."
   

3. With progname.

     logger.info('initialize') { "Initializing..." }
   

4. With severity.

     logger.add(Logger::FATAL) { 'Fatal error!' }
   

Setting severity threshold

1. Original interface.

     logger.sev_threshold = Logger::WARN
   

2. Log4r (somewhat) compatible interface.

     logger.level = Logger::INFO
   
     DEBUG < INFO < WARN < ERROR < FATAL < UNKNOWN