class ActiveSupport::LogSubscriber - activesupport-4.2.3 Documentation

# class ActiveSupport::LogSubscriber

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.

### Constants

BLACK

  Colors

BLUE
BOLD
CLEAR

  Embed in a String to clear all previous ANSI sequences.

CYAN
GREEN
MAGENTA
RED
WHITE
YELLOW

### Attributes

logger[W]

### Public Class Methods

flush_all!() click to toggle source

Flush all ::log_subscribers' logger.

    # File lib/active_support/log_subscriber.rb, line 69
    def flush_all!
      logger.flush if logger.respond_to?(:flush)
    end

log_subscribers() click to toggle source

    # File lib/active_support/log_subscriber.rb, line 64
    def log_subscribers
      subscribers
    end

logger() click to toggle source

    # File lib/active_support/log_subscriber.rb, line 56
    def logger
      @logger ||= if defined?(Rails) && Rails.respond_to?(:logger)
        Rails.logger
      end
    end

### Public Instance Methods

finish(name, id, payload) click to toggle source
Calls superclass method

    # File lib/active_support/log_subscriber.rb, line 82
    def finish(name, id, payload)
      super if logger
    rescue Exception => e
      logger.error "Could not log #{name.inspect} event. #{e.class}: #{e.message} #{e.backtrace}"
    end

logger() click to toggle source

    # File lib/active_support/log_subscriber.rb, line 74
    def logger
      LogSubscriber.logger
    end

start(name, id, payload) click to toggle source
Calls superclass method

    # File lib/active_support/log_subscriber.rb, line 78
    def start(name, id, payload)
      super if logger
    end

### Protected Instance Methods

color(text, color, bold=false) click to toggle source

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.

    # File lib/active_support/log_subscriber.rb, line 102
    def color(text, color, bold=false)
      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