Example of unfair scheduling using queue.Queue in CPython

unfair_queue.py

from threading import Thread, get_ident
import time
from queue import Queue

THREAD_COUNT = 10
POOL_GET_TIMEOUT = 10.0
POOL_SIZE = 2

pool = Queue()
for i in range(POOL_SIZE):
    pool.put(i)


def work():
    """ Grabs an item from the pool (e.g. a connection pool) and does some
    blocking work with it """
    pool_item = pool.get(timeout=POOL_GET_TIMEOUT)
    print("Doing work", get_ident())
    time.sleep(0.05) # Simulate some blocking work
    pool.put(pool_item)


def thread_start(work_items):
    """ Example thread daemon that takes and proccesses a list of work items """
    for work_item in work_items:
        work_item()


threads = [
    Thread(target=thread_start, args=([work for _ in range(1000)], ))
    for tid in range(THREAD_COUNT)
]
for thread in threads:
    thread.start()
for thread in threads:
    thread.join()