Class: ActiveSupport::LogSubscriber

Inherits:
Object
  • Object
show all
Defined in:
activesupport/lib/active_support/log_subscriber.rb,
activesupport/lib/active_support/log_subscriber/test_helper.rb

Overview

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.

Defined Under Namespace

Modules: TestHelper

Constant Summary collapse

CLEAR =

Embed in a String to clear all previous ANSI sequences.

"\e[0m"
BOLD = 
"\e[1m"
BLACK =

Colors

"\e[30m"
RED = 
"\e[31m"
GREEN = 
"\e[32m"
YELLOW = 
"\e[33m"
BLUE = 
"\e[34m"
MAGENTA = 
"\e[35m"
CYAN = 
"\e[36m"
WHITE = 
"\e[37m"

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.attach_to(namespace, log_subscriber = new, notifier = ActiveSupport::Notifications) ⇒ Object 



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# 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! ⇒ Object

Flush all log_subscribers’ logger.



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# File 'activesupport/lib/active_support/log_subscriber.rb', line 83

def flush_all!
  flushable_loggers.each { |log| log.flush }
end

.flushable_loggers ⇒ Object 



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# 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

.log_subscribers ⇒ Object 



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

def log_subscribers
  @@log_subscribers ||= []
end

.logger ⇒ Object 



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# File 'activesupport/lib/active_support/log_subscriber.rb', line 55

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

Instance Method Details

#call(message, *args) ⇒ Object 



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# 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