class ActiveSupport::LogSubscriber

ActiveSupport::LogSubscriber is an object set to consume ActiveSupport::Notifications with the sole purpose of logging them. The log subscriber dispatches notifications to a registered object based on its given namespace.

An example would be Active Record log subscriber responsible for logging queries:

module ActiveRecord
  class LogSubscriber < ActiveSupport::LogSubscriber
    def sql(event)
      "#{event.payload[:name]} (#{event.duration}) #{event.payload[:sql]}"
    end
  end
end

And it's finally registered as:

ActiveRecord::LogSubscriber.attach_to :active_record

Since we need to know all instance methods before attaching the log subscriber, the line above should be called after your ActiveRecord::LogSubscriber definition.

After configured, whenever a “sql.active_record” notification is published, it will properly dispatch the event (ActiveSupport::Notifications::Event) to the sql method.

Log subscriber also has some helpers to deal with logging and automatically flushes all logs when the request finishes (via action_dispatch.callback notification) in a Rails environment.

Constants

BLACK: Colors
BLUE
BOLD
CLEAR: Embed in a String to clear all previous ANSI sequences.
CYAN
GREEN
MAGENTA
RED
WHITE
YELLOW

Attributes

logger[W]

Public Class Methods

flush_all!() click to toggle source

Flush all log_subscribers' logger.

# File lib/active_support/log_subscriber.rb, line 70
def flush_all!
  logger.flush if logger.respond_to?(:flush)
end

log_subscribers() click to toggle source

# File lib/active_support/log_subscriber.rb, line 65
def log_subscribers
  subscribers
end

logger() click to toggle source

# File lib/active_support/log_subscriber.rb, line 57
def logger
  @logger ||= if defined?(Rails) && Rails.respond_to?(:logger)
    Rails.logger
  end
end

Public Instance Methods

finish(name, id, payload) click to toggle source

Calls superclass method

# File lib/active_support/log_subscriber.rb, line 83
def finish(name, id, payload)
  super if logger
rescue => e
  if logger
    logger.error "Could not log #{name.inspect} event. #{e.class}: #{e.message} #{e.backtrace}"
  end
end

logger() click to toggle source

# File lib/active_support/log_subscriber.rb, line 75
def logger
  LogSubscriber.logger
end

start(name, id, payload) click to toggle source

Calls superclass method

# File lib/active_support/log_subscriber.rb, line 79
def start(name, id, payload)
  super if logger
end

Private Instance Methods

color(text, color, bold = false) click to toggle source

Set color by using a symbol or one of the defined constants. If a third option is set to true, it also adds bold to the string. This is based on the Highline implementation and will automatically append CLEAR to the end of the returned String.

# File lib/active_support/log_subscriber.rb, line 105
def color(text, color, bold = false) # :doc:
  return text unless colorize_logging
  color = self.class.const_get(color.upcase) if color.is_a?(Symbol)
  bold  = bold ? BOLD : ""
  "#{bold}#{color}#{text}#{CLEAR}"
end