class ActiveSupport::BroadcastLogger

Active Support Broadcast Logger¶ ↑

The Broadcast logger is a logger used to write messages to multiple IO. It is commonly used in development to display messages on STDOUT and also write them to a file (development.log). With the Broadcast logger, you can broadcast your logs to a unlimited number of sinks.

The BroadcastLogger acts as a standard logger and all methods you are used to are available. However, all the methods on this logger will propagate and be delegated to the other loggers that are part of the broadcast.

Broadcasting your logs.

stdout_logger = Logger.new(STDOUT)
file_logger   = Logger.new("development.log")
broadcast = BroadcastLogger.new(stdout_logger, file_logger)

broadcast.info("Hello world!") # Writes the log to STDOUT and the development.log file.

Add a logger to the broadcast.

stdout_logger = Logger.new(STDOUT)
broadcast = BroadcastLogger.new(stdout_logger)
file_logger   = Logger.new("development.log")
broadcast.broadcast_to(file_logger)

broadcast.info("Hello world!") # Writes the log to STDOUT and the development.log file.

Modifying the log level for all broadcasted loggers.

stdout_logger = Logger.new(STDOUT)
file_logger   = Logger.new("development.log")
broadcast = BroadcastLogger.new(stdout_logger, file_logger)

broadcast.level = Logger::FATAL # Modify the log level for the whole broadcast.

Stop broadcasting log to a sink.

stdout_logger = Logger.new(STDOUT)
file_logger   = Logger.new("development.log")
broadcast = BroadcastLogger.new(stdout_logger, file_logger)
broadcast.info("Hello world!") # Writes the log to STDOUT and the development.log file.

broadcast.stop_broadcasting_to(file_logger)
broadcast.info("Hello world!") # Writes the log *only* to STDOUT.

At least one sink has to be part of the broadcast. Otherwise, your logs will not be written anywhere. For instance:

broadcast = BroadcastLogger.new
broadcast.info("Hello world") # The log message will appear nowhere.

If you are adding a custom logger with custom methods to the broadcast, the ‘BroadcastLogger` will proxy them and return the raw value, or an array of raw values, depending on how many loggers in the broadcasts responded to the method:

class MyLogger < ::Logger
  def loggable?
    true
  end
end

logger = BroadcastLogger.new
logger.loggable? # => A NoMethodError exception is raised because no loggers in the broadcasts could respond.

logger.broadcast_to(MyLogger.new(STDOUT))
logger.loggable? # => true
logger.broadcast_to(MyLogger.new(STDOUT))
puts logger.broadcasts # => [MyLogger, MyLogger]
logger.loggable? # [true, true]

# File activesupport/lib/active_support/broadcast_logger.rb, line 81
def initialize(*loggers)
  @broadcasts = []
  @progname = "Broadcast"

  broadcast_to(*loggers)
end

broadcast_logger = ActiveSupport::BroadcastLogger.new
broadcast_logger.broadcast_to(Logger.new(STDOUT), Logger.new(STDERR))

# File activesupport/lib/active_support/broadcast_logger.rb, line 92
def broadcast_to(*loggers)
  @broadcasts.concat(loggers)
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 146
def debug!
  dispatch(:debug!)
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 141
def debug?
  @broadcasts.any? { |logger| logger.debug? }
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 179
def error!
  dispatch(:error!)
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 174
def error?
  @broadcasts.any? { |logger| logger.error? }
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 190
def fatal!
  dispatch(:fatal!)
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 185
def fatal?
  @broadcasts.any? { |logger| logger.fatal? }
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 157
def info!
  dispatch(:info!)
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 152
def info?
  @broadcasts.any? { |logger| logger.info? }
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 194
def initialize_copy(other)
  @broadcasts = []
  @progname = other.progname.dup

  broadcast_to(*other.broadcasts.map(&:dup))
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 135
def level
  @broadcasts.map(&:level).min
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 113
def local_level
  loggers = @broadcasts.select { |logger| logger.respond_to?(:local_level) }

  loggers.map do |logger|
    logger.local_level
  end.first
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 107
def local_level=(level)
  @broadcasts.each do |logger|
    logger.local_level = level if logger.respond_to?(:local_level=)
  end
end

sink = Logger.new(STDOUT)
broadcast_logger = ActiveSupport::BroadcastLogger.new

broadcast_logger.stop_broadcasting_to(sink)

# File activesupport/lib/active_support/broadcast_logger.rb, line 103
def stop_broadcasting_to(logger)
  @broadcasts.delete(logger)
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 168
def warn!
  dispatch(:warn!)
end

# File activesupport/lib/active_support/broadcast_logger.rb, line 163
def warn?
  @broadcasts.any? { |logger| logger.warn? }
end