Code for the "A simple and pragmatic approach to fixing a memory leak" talk at RailsConf 2023

client_middleware.rb

# This middleware dynamically switch a job queue based on its class name. 

module TroubleshootMemoryMiddleware
  module Client
    class CustomQueueName
      QUARANTINE_QUEUE = "quarantine"

      def call(worker_class, job, queue, redis_pool)
        # Jobs enqueued without ActiveJob are not wrapped.
        job_class_name = if job["wrapped"].present?
          job["wrapped"].name
        else
          job["class"]
        end

        quarantined_jobs = parse_quarantined_jobs

        if quarantined_jobs.include?(job_class_name)
          job["queue"] = QUARANTINE_QUEUE
        end

        yield
      end

      private

      def parse_quarantined_jobs
        if ENV["QUARANTINED_JOBS"].present?
          ENV["QUARANTINED_JOBS"].split(";")
        else
          []
        end
      end
    end
  end
end

jobs_list.rb

# Scrip to get the jobs enqueued in the `default` queue. 
# put this in your Rails repo and
# run it: rails runner jobs_list.rb

# jobs_list.rb
filepaths = Dir.glob("app/jobs/**/*.rb")

ActiveSupport::Inflector.inflections(:en) do |inflect|
  inflect.acronym "EHawk"
end

jobs_queued_as_defaults = []

filepaths.each do |filepath|
  _, job_path = filepath.split("app/jobs/")

  class_name = job_path
    .gsub(".rb", "")
    .split("/")
    .map { |s| ActiveSupport::Inflector.camelize(s, true) }
    .join("::")

  job_class = ActiveSupport::Inflector.constantize(class_name)
  
  # Some jobs do not inherit from `ApplicationJob` like Periodic jobs, and do not respond to `queue_name`. 
  # Their queue is default
  if !job_class.respond_to?(:queue_name) || (job_class.respond_to?(:queue_name) && job_class.queue_name == "default")
    jobs_queued_as_defaults << job_class
  end
end

puts jobs_queued_as_defaults

sidekiq.rb

# config/initializers/sidekiq.rb

Sidekiq.configure_client do |config|
  config.client_middleware do |chain|
    chain.add TroubleshootMemoryMiddleware::Client::CustomQueueName
  end
end