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.
- A
- C
- F
- L
CLEAR | = | "\e[0m" |
Embed in a String to clear all previous ANSI sequences. |
||
BOLD | = | "\e[1m" |
BLACK | = | "\e[30m" |
Colors |
||
RED | = | "\e[31m" |
GREEN | = | "\e[32m" |
YELLOW | = | "\e[33m" |
BLUE | = | "\e[34m" |
MAGENTA | = | "\e[35m" |
CYAN | = | "\e[36m" |
WHITE | = | "\e[37m" |
Source: show
# File activesupport/lib/active_support/log_subscriber.rb, line 59 def attach_to(namespace, log_subscriber=new, notifier=ActiveSupport::Notifications) log_subscribers << log_subscriber @@flushable_loggers = nil log_subscriber.public_methods(false).each do |event| next if 'call' == event.to_s notifier.subscribe("#{event}.#{namespace}", log_subscriber) end end
Flush all ::log_subscribers’ logger.
Source: show
# File activesupport/lib/active_support/log_subscriber.rb, line 83 def flush_all! flushable_loggers.each { |log| log.flush } end
Source: show
# File activesupport/lib/active_support/log_subscriber.rb, line 74 def flushable_loggers @@flushable_loggers ||= begin loggers = log_subscribers.map(&:logger) loggers.uniq! loggers.select { |l| l.respond_to?(:flush) } end end
Source: show
# File activesupport/lib/active_support/log_subscriber.rb, line 70 def log_subscribers @@log_subscribers ||= [] end
Source: show
# File activesupport/lib/active_support/log_subscriber.rb, line 55 def logger @logger ||= Rails.logger if defined?(Rails) end
Source: show
# File activesupport/lib/active_support/log_subscriber.rb, line 88 def call(message, *args) return unless logger method = message.split('.').first begin send(method, ActiveSupport::Notifications::Event.new(message, *args)) rescue Exception => e logger.error "Could not log #{message.inspect} event. #{e.class}: #{e.message}" end 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 the Highline implementation and will automatically append CLEAR to the end of the returned String.
Source: show
# File activesupport/lib/active_support/log_subscriber.rb, line 115 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