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log_subscriber.rb
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log_subscriber.rb
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# frozen_string_literal: true
require "active_support/core_ext/module/attribute_accessors"
require "active_support/core_ext/class/attribute"
require "active_support/core_ext/enumerable"
require "active_support/subscriber"
require "active_support/deprecation/proxy_wrappers"
module ActiveSupport
# = Active Support Log \Subscriber
#
# +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
# attach_to :active_record
#
# def sql(event)
# info "#{event.payload[:name]} (#{event.duration}) #{event.payload[:sql]}"
# end
# end
# end
#
# ActiveRecord::LogSubscriber.logger must be set as well, but it is assigned
# automatically in a \Rails environment.
#
# After configured, whenever a <tt>"sql.active_record"</tt> notification is
# published, it will properly dispatch the event
# (ActiveSupport::Notifications::Event) to the +sql+ method.
#
# Being an ActiveSupport::Notifications consumer,
# +ActiveSupport::LogSubscriber+ exposes a simple interface to check if
# instrumented code raises an exception. It is common to log a different
# message in case of an error, and this can be achieved by extending
# the previous example:
#
# module ActiveRecord
# class LogSubscriber < ActiveSupport::LogSubscriber
# def sql(event)
# exception = event.payload[:exception]
#
# if exception
# exception_object = event.payload[:exception_object]
#
# error "[ERROR] #{event.payload[:name]}: #{exception.join(', ')} " \
# "(#{exception_object.backtrace.first})"
# else
# # standard logger code
# end
# end
# end
# end
#
# +ActiveSupport::LogSubscriber+ also has some helpers to deal with
# logging. For example, ActiveSupport::LogSubscriber.flush_all! will ensure
# that all logs are flushed, and it is called in Rails::Rack::Logger after a
# request finishes.
class LogSubscriber < Subscriber
# ANSI sequence modes
MODES = {
clear: 0,
bold: 1,
italic: 3,
underline: 4,
}
# ANSI sequence 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"
mattr_accessor :colorize_logging, default: true
class_attribute :log_levels, instance_accessor: false, default: {} # :nodoc:
LEVEL_CHECKS = {
debug: -> (logger) { !logger.debug? },
info: -> (logger) { !logger.info? },
error: -> (logger) { !logger.error? },
}
class << self
def logger
@logger ||= if defined?(Rails) && Rails.respond_to?(:logger)
Rails.logger
end
end
def attach_to(...) # :nodoc:
result = super
set_event_levels
result
end
attr_writer :logger
def log_subscribers
subscribers
end
# Flush all log_subscribers' logger.
def flush_all!
logger.flush if logger.respond_to?(:flush)
end
private
def fetch_public_methods(subscriber, inherit_all)
subscriber.public_methods(inherit_all) - LogSubscriber.public_instance_methods(true)
end
def set_event_levels
if subscriber
subscriber.event_levels = log_levels.transform_keys { |k| "#{k}.#{namespace}" }
end
end
def subscribe_log_level(method, level)
self.log_levels = log_levels.merge(method => LEVEL_CHECKS.fetch(level))
set_event_levels
end
end
def initialize
super
@event_levels = {}
end
def logger
LogSubscriber.logger
end
def silenced?(event)
logger.nil? || @event_levels[event]&.call(logger)
end
def call(event)
super if logger
rescue => e
log_exception(event.name, e)
end
def publish_event(event)
super if logger
rescue => e
log_exception(event.name, e)
end
attr_writer :event_levels # :nodoc:
private
%w(info debug warn error fatal unknown).each do |level|
class_eval <<-METHOD, __FILE__, __LINE__ + 1
def #{level}(progname = nil, &block)
logger.#{level}(progname, &block) if logger
end
METHOD
end
# Set color by using a symbol or one of the defined constants. Set modes
# by specifying bold, italic, or underline options. Inspired by Highline,
# this method will automatically clear formatting at the end of the returned String.
def color(text, color, mode_options = {}) # :doc:
return text unless colorize_logging
color = self.class.const_get(color.upcase) if color.is_a?(Symbol)
mode = mode_from(mode_options)
clear = "\e[#{MODES[:clear]}m"
"#{mode}#{color}#{text}#{clear}"
end
def mode_from(options)
modes = MODES.values_at(*options.compact_blank.keys)
"\e[#{modes.join(";")}m" if modes.any?
end
def log_exception(name, e)
if logger
logger.error "Could not log #{name.inspect} event. #{e.class}: #{e.message} #{e.backtrace}"
end
end
end
end