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require 'active_support/core_ext/class/inheritable_attributes'
require 'active_support/notifications'
module Rails
# Rails::Subscriber is an object set to consume ActiveSupport::Notifications
# on initialization with the sole purpose of logging. The subscriber dispatches
# notifications to a registered object based on it's given namespace.
#
# An example would be an Active Record subscriber responsible for logging queries:
#
# module ActiveRecord
# class Railtie
# class Subscriber < Rails::Subscriber
# def sql(event)
# "#{event.payload[:name]} (#{event.duration}) #{event.payload[:sql]}"
# end
# end
# end
# end
#
# Which would be registed as:
#
# Rails::Subscriber.add :active_record, ActiveRecord::Railtie::Subscriber.new
#
# So whenever an +active_record.sql+ notification arrives to Rails::Subscriber,
# it will properly dispatch the event (ActiveSupport::Notifications::Event) to
# the sql method.
#
# This avoids spanning several subscribers just for logging purposes
# (which slows down the main thread). It also provides a centralized
# facility on top of Rails.logger.
#
# Subscriber also has some helpers to deal with logging and automatically flushes
# all logs when the request finishes (via action_dispatch.callback notification).
class Subscriber
mattr_accessor :colorize_logging, :log_tailer
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, subscriber)
subscribers[namespace.to_sym] = subscriber
end
def self.subscribers
@subscribers ||= {}
end
def self.dispatch(args)
namespace, name = args[0].split(".")
subscriber = subscribers[namespace.to_sym]
if subscriber.respond_to?(name) && subscriber.logger
subscriber.send(name, ActiveSupport::Notifications::Event.new(*args))
end
if args[0] == "action_dispatch.after_dispatch" && !subscribers.empty?
flush_all!
log_tailer.tail! if log_tailer
end
end
# Flush all subscribers' logger.
def self.flush_all!
loggers = subscribers.values.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)
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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