Relaton::Logger is a Ruby gem that implements a logger for Relaton gems. It is also possible to use this gem as a standalone logger.

Installation

Install the gem and add to the application’s Gemfile by executing:

$ bundle add relaton-logger

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install relaton-logger

Usage

The Relaton::Logger gem provides a logger pool that can be used to log messages. The logger pool is a singleton and can be accessed by calling Relaton.logger_pool. The logger pool is an Array that contains loggers. By default, the logger pool contains a single logger, which is an instance of Relaton::Logger::Log class, which inherits the Logger class from the Ruby standard library.

The logger pool can be used to log messages by calling the methods of the loggers in the pool. These methods are the same as the methods of the Logger class from the Ruby standard library (debug, info, warn, error, fatal, unknown).

require "relaton/logger"

Relaton.logger_pool.info "message"
INFO: message

The program name and the key can be passed as arguments to the log methods. The program name is a string that is added to the log message. The key is a string that is added to the log message in parentheses.

Relaton.logger_pool.warn "message", "progname", key: "KEY"
[progname] WARN: (KEY) message

The block form of the log methods can be used to log messages that are expensive to generate. The block is called only if the message is logged.

Relaton.logger_pool.error("progname", key: "KEY") { "message" }
[progname] ERROR: (KEY) message

The logger pool can be configured to contain multiple loggers. Initially, there is one :default logger. Any instance of loggers in the logger pool are accessible with [] method. To add or replace a logger use []= method of the logger pool and pass the logger as an argument. The loggers in the pool are called in the order they are added to the pool.

# Access logger
Relaton.logger_pool[:default]
 =>
#<Relaton::Logger::Log:0x00000001212068c8

# Add a new logger
Relaton.logger_pool[:file] = Relaton::Logger::Log.new("relaton.log", levels: [:info, :warn])

To change the log level of a logger, call the level= method of the logger.

Relaton.logger_pool[:default].levels = [:info, :warn, :error]
Relaton.logger_pool[:default].add_level :fatal
Relaton.logger_pool[:default].remove_level :warn

To create a new logger, call the new method of the Relaton::Logger::Log class and pass arguments:

• logdev - file name or an IO object. If nil or File::NULL, messages are not logged. If it is a file name, the file is opened in append mode. If it is an IO object, messages are written to it.

• shift_age - the number of old log files to keep. If 0, no old log files are kept. If it is a number, old log files are kept and the log file is rotated when it reaches the maximum size. If it is a string, old log files are kept and the log file is rotated when it reaches the maximum size. The string is a time unit and a number, for example, "daily 7" or "weekly 4". Default is 0.

• shift_size - the maximum size of the log file. If it is a number, the log file is rotated when it reaches the maximum size. If it is a string, the log file is rotated when it reaches the maximum size. The string is a number and a time unit, for example, "1048576" or "1M". Default is 1048576.

• levels - an array of symbols that represent the log levels The log levels are :debug, :info, :warn, :error, :fatal, :unknown. Default is [:info, :warn, :error, :fatal, :unknown].

• formatter - a formatter object that is used to format the log messages. Two formatters are available at this moment Relaton::Logger::FormatterString, Relaton::Logger::FormatterJson, and Proc. The default formater is Relaton::Logger::FormatterString.

• progname - a string that is added to the log message. Default is nil.

Relaton::Logger::Log.new("relaton.log", levels: [:info, :warn], formatter: Relaton::Logger::FormatterJSON, progname: "progname")

To create a custom formatter implement a class with the call method which takes agruments:

• severity - the log level

• time - the time the message was logged

• progname - the program name

• msg - the message

• any other keyword arguments that are passed to the log method, for example, key

class CustomFormatter
  def call(severity, time, progname, msg, key: "Key 1")
    "#{time} [#{severity}] #{progname} (#{key}): #{msg}\n"
  end
end

Relaton::Logger::Log.new("relaton.log", formatter: CustomFormatter)

It’s possible to use Proc as a formatter. The Proc object is called with the same arguments as the call method of the custom formatter.

log = Relaton::Logger::Log.new("relaton.log")

log.formatter = Proc.new do |severity, time, progname, msg, key: "Key 1"|
  "#{time} [#{severity}] #{progname} (#{key}): #{msg}\n"
end

A log file can be cleared by calling the truncate method of the logger pool.

Relaton.logger_pool.truncate

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to [rubygems.org](https://rubygems.org).

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/relaton/relaton-logger.

License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).