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Class: ActiveSupport::LogSubscriber

Relationships & Source Files
Namespace Children
Modules:
TestHelper
Extension / Inclusion / Inheritance Descendants
Subclasses:
ActionController::LogSubscriber, ActionMailer::LogSubscriber, ActionView::LogSubscriber, ActiveRecord::LogSubscriber, ActiveStorage::LogSubscriber, ActiveJob::Logging::LogSubscriber, Rails::Rack::Logger
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, Subscriber
Instance Chain:
self, Subscriber
Inherits: ActiveSupport::Subscriber
Defined in: activesupport/lib/active_support/log_subscriber.rb,
activesupport/lib/active_support/log_subscriber/test_helper.rb

Overview

LogSubscriber is an object set to consume 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.

Constant Summary

Class Attribute Summary

Class Method Summary

Subscriber - Inherited

.attach_to

Attach the subscriber to a namespace.
.method_added

Adds event subscribers for all new methods added to the class.
.new, .subscribers, .add_event_subscriber

Instance Attribute Summary

Instance Method Summary

Subscriber - Inherited

#finish, #start

Constructor Details

This class inherits a constructor from ActiveSupport::Subscriber

Class Attribute Details

.colorize_logging (rw) Also known as: #colorize_logging

[ GitHub ] 

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 54



mattr_accessor :colorize_logging, default: true


  








  

    .logger   (rw)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 57



def logger
  @logger ||= if defined?(Rails) && Rails.respond_to?(:logger)
    Rails.logger
  end
end


  








  

    .logger=(value)   (rw)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 63



attr_writer :logger


  







Class Method Details



  

    .flush_all!  
  



  

    

Flush all log_subscribers’ logger.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 70



def flush_all!
  logger.flush if logger.respond_to?(:flush)
end


  








  

    .log_subscribers  
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 65



def log_subscribers
  subscribers
end


  







Instance Attribute Details



  

    #colorize_logging   (rw)
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 54



mattr_accessor :colorize_logging, default: true


  







Instance Method Details



  

    #color(text, color, bold = false)   (private)
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'activesupport/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


  








  

    #finish(name, id, payload)  
  

  [ GitHub ]


  

  


# File 'activesupport/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  
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 75



def logger
  LogSubscriber.logger
end


  








  

    #start(name, id, payload)  
  

  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/log_subscriber.rb', line 79



def start(name, id, payload)
  super if logger
end