Example of what Delayed::Plugins::YouthInAsiaPlugin might look like

djyiap.rb

# Automatically kill jobs' worker when it finishes
# if it used more memory than allotted.

# Ali-G:  Lets talk about doctors who is ending the life of people who is suffering.
# Ali-G   What’s it got to do with the youth in Asia I mean it aiint their fault these peoples is dying, they’s thousands of miles away.
# Doctor: Euthanasia means mercy killing, it literally means dying well. We're not talking about the youth in Asia, (or) the youth in Africa.
# Ali-G:  But why is you blaming that on the asian kids or whatever?
module Delayed
  module Plugins
    class YouthInAsiaPlugin < Delayed::Plugin

      # Add an additional pad factor to the memory sample. 
      MEMORY_THRESHOLD_FACTOR = 1.10

      callbacks do |lifecycle|
        lifecycle.after(:perform) do |worker, job|
          after_perform_sample = memory_sample

          # Heroku workers don’t have knowledge of their dyno size by default. We wrote a mixin to
          # extend a worker to have knowledge of its underlying dyno metadata. We fetch the metadata from the
          # Heroku API when the worker is started. If you arent using heroku you should be able to access
          # memory capacity via a shell command, or java vm argument.
          worker.stop if worker.exceeds_memory_ceiling?(after_perform_sample * MEMORY_THRESHOLD_FACTOR)
        end
      end
      
      private
      # Sample is environment dependent
      # JRuby would use something like:
      #    java.lang.Runtime.getRuntime.totalMemory / (1024 * 1024).to_f
      # Most unix systems will use some variant of the process status ‘ps’ command
      #    `ps -o rss #{$$}`.split("\n")[1].to_f / 1024.0
      # Heroku is using a linux container so we’ll fetch it from the proc status file
      def self.memory_sample
        if File.open("/proc/#{$$}/status", "r") {|f| f.read } =~ /RSS:\s*(\d+) kB/i
          return $1.to_f / 1024.0
        end
      end
    end
  end
end