Unless I'm misunderstanding, it sounds like your use case fits RabbitMQ perfectly. Pseudocode:

    while True:
      message = queue.consume()
      process(message)
      message.ack()

RabbitMQ will automatically put the message back on the queue when the consumer that pulled it disconnects w/o acknowledging it first. Alternatively, you could explicitly reject messages:

    while True:
      message = queue.consume()
      try:
        process(message)
      except Exception:
        message.reject()
        raise

If you're using Python you might want to check out Dramatiq[1]

[1]: https://dramatiq.io