thread_pool_with_sized_queue

🔧 Implement a Bounded Thread Pool with SizedQueue

To avoid unbounded thread growth under load and to propagate errors gracefully, combine SizedQueue with a fixed worker set. Producers push jobs into the queue, workers pull and execute them, and you can signal shutdown by pushing special sentinel values.

require 'thread'

class ThreadPool
  def initialize(size, queue_size)
    @jobs      = SizedQueue.new(queue_size)
    @workers   = Array.new(size) do |i|
      Thread.new do
        loop do
          job = @jobs.pop
          break if job == :shutdown
          begin
            job.call
          rescue => e
            warn "Worker \\##{i} failed: #{e.message}"
          end
        end
      end
    end
  end

  def schedule(&block)
    @jobs.push(block)
  end

  def shutdown
    @workers.size.times { @jobs.push(:shutdown) }
    @workers.each(&:join)
  end
end

# Usage
pool = ThreadPool.new(5, 50)
100.times { |i| pool.schedule { puts "Job #{i}" } }
pool.shutdown

This setup enforces back-pressure (via SizedQueue), catches per-job exceptions, and cleanly joins all threads on shutdown.