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require 'active_support/core_ext/class/inheritable_attributes'
require 'active_support/notifications'
module Rails
# Rails::LogSubscriber is an object set to consume ActiveSupport::Notifications
# on initialization with solely purpose of logging. The log subscriber dispatches
# notifications to a regirested object based on its given namespace.
#
# An example would be ActiveRecord log subscriber responsible for logging queries:
#
# module ActiveRecord
# class Railtie
# class LogSubscriber < Rails::LogSubscriber
# def sql(event)
# "#{event.payload[:name]} (#{event.duration}) #{event.payload[:sql]}"
# end
# end
# end
# end
#
# It's finally registed as:
#
# Rails::LogSubscriber.add :active_record, ActiveRecord::Railtie::LogSubscriber.new
#
# So whenever a "active_record.sql" notification arrive to Rails::LogSubscriber,
# it will properly dispatch the event (ActiveSupport::Notifications::Event) to
# the sql method.
#
# This is useful because it avoids spanning several log subscribers just for logging
# purposes(which slows down the main thread). Besides of providing a centralized
# facility on top of Rails.logger.
#
# Log subscriber also has some helpers to deal with logging and automatically flushes
# all logs when the request finishes (via action_dispatch.callback notification).
class LogSubscriber
mattr_accessor :colorize_logging
self.colorize_logging = true
# Embed in a String to clear all previous ANSI sequences.
CLEAR = "\e[0m"
BOLD = "\e[1m"
# Colors
BLACK = "\e[30m"
RED = "\e[31m"
GREEN = "\e[32m"
YELLOW = "\e[33m"
BLUE = "\e[34m"
MAGENTA = "\e[35m"
CYAN = "\e[36m"
WHITE = "\e[37m"
def self.add(namespace, log_subscriber, notifier = ActiveSupport::Notifications)
log_subscribers << log_subscriber
log_subscriber.public_methods(false).each do |event|
notifier.subscribe("#{namespace}.#{event}") do |*args|
next if log_subscriber.logger.nil?
begin
log_subscriber.send(event, ActiveSupport::Notifications::Event.new(*args))
rescue Exception => e
Rails.logger.error "Could not log #{args[0].inspect} event. #{e.class}: #{e.message}"
end
end
end
end
def self.log_subscribers
@log_subscribers ||= []
end
# Flush all log_subscribers' logger.
def self.flush_all!
loggers = log_subscribers.map(&:logger)
loggers.uniq!
loggers.each { |l| l.flush if l.respond_to?(:flush) }
end
# By default, we use the Rails.logger for logging.
def logger
Rails.logger
end
protected
%w(info debug warn error fatal unknown).each do |level|
class_eval <<-METHOD, __FILE__, __LINE__ + 1
def #{level}(*args, &block)
return unless logger
logger.#{level}(*args, &block)
end
METHOD
end
# Set color by using a string 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 Highline implementation and it automatically appends CLEAR to the end
# of the returned String.
#
def color(text, color, bold=false)
return text unless colorize_logging
color = self.class.const_get(color.to_s.upcase) if color.is_a?(Symbol)
bold = bold ? BOLD : ""
"#{bold}#{color}#{text}#{CLEAR}"
end
end
end
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