我正在使用 Celery 执行异步后台任务，Redis 作为后端。我对芹菜工人在以下情况下的行为感兴趣：
我正在使用 celeryd 将 worker 作为守护程序运行。已为此工作人员分配了两个队列，可通过 -Q 选项使用：
celeryd -E -Q queue1,queue2
工作人员如何决定从何处获取下一个要使用的任务？它是随机消耗来自queue1或queue2的任务吗？它会优先考虑从queue1中获取，因为它在传递给-Q的参数列表中排在第一位？
根据我的测试，它以循环方式处理多个队列。
如果我使用此测试代码：
from celery import task
import time
@task
def my_task(item_id):
time.sleep(0.5)
print('Processing item "%s"...' % item_id)
def add_items_to_queue(queue_name, items_count):
for i in xrange(0, items_count):
my_task.apply_async(('%s-%d' % (queue_name, i),), queue=queue_name)
add_items_to_queue('queue1', 10)
add_items_to_queue('queue2', 10)
add_items_to_queue('queue3', 5)
并用（使用 django-celery）开始队列：
`manage.py celery worker -Q queue1,queue2,queue3`
它输出：
Processing item "queue1-0"...
Processing item "queue3-0"...
Processing item "queue2-0"...
Processing item "queue1-1"...
Processing item "queue3-1"...
Processing item "queue2-1"...
Processing item "queue1-2"...
Processing item "queue3-2"...
Processing item "queue2-2"...
Processing item "queue1-3"...
Processing item "queue3-3"...
Processing item "queue2-3"...
Processing item "queue1-4"...
Processing item "queue3-4"...
Processing item "queue2-4"...
Processing item "queue1-5"...
Processing item "queue2-5"...
Processing item "queue1-6"...
Processing item "queue2-6"...
Processing item "queue1-7"...
Processing item "queue2-7"...
Processing item "queue1-8"...
Processing item "queue2-8"...
Processing item "queue1-9"...
Processing item "queue2-9"...
从每个队列中提取一个项目，即使所有 queue1 任务都是在 queue2 和 3 任务之前发布的。
注意：正如@WarLord指出的那样，仅当CELERYD_PREFETCH_MULTIPLIER设置为 1 时，此确切行为才有效。 如果它大于 1，则意味着将从队列中批量获取项目。 因此，如果您有 4 个进程，PREFETCH_MULTIPLIER设置为 4，这意味着将立即从队列中提取 16 个项目，因此您不会得到上述确切的输出，但它仍然大致遵循循环。
注意：此答案已弃用：最新版本的 Celery 的工作方式与 2013 年大不相同......
使用多个队列的工作线程消耗任务，FIFO 顺序也在多个队列中维护。
例：
队列 1 ： （t1， t2， t5， t7） 队列 2 ： （t0，t3，t4，t6）
假设 0-7 表示已发布任务的顺序
消耗顺序为 t0， t1， t2， t3， t4， t5， t6， t7
使用 pyamqp 代理库指向 rabbitmq 服务器，任务以循环方式处理。请参阅下面的证明。
似乎处理任务的顺序是由代理库决定的，而不是实际的后端（rabbitmq 与 redis 不是问题）。
软件版本：
$ pip freeze | egrep "celery|kombu|amqp"
amqp==2.5.2
celery==4.4.2
kombu==4.6.8
from time import sleep
@app.task
def sleepy(name):
print(f"Processing: {name}")
sleep(0.5)
然后在另一个 shell 中，将任务排队：
from time import sleep
def queue_them():
for x in range(50):
sleepy.apply_async(args=(f"Q1-T{x}",), queue="Q1")
sleep(0.1)
for x in range(20):
sleepy.apply_async(args=(f"Q2-T{x}",), queue="Q2")
sleep(0.1)
sleepy.apply_async(args=("Q3-T0",), queue="Q3")
for x in range(30):
sleepy.apply_async(args=(f"Q2MOAR-T{x}",), queue="Q2")
# setup - get celery to setup the queues and exchanges
sleepy.apply_async(args=("nothing",), queue="Q1")
sleepy.apply_async(args=("nothing",), queue="Q2")
sleepy.apply_async(args=("nothing",), queue="Q3")
# run the test
queue_them()
在另一个壳中，运行芹菜：
$ celery worker -A myapp.celery --pool=prefork --concurrency=2 -Ofair --queues=Q1,Q3,Q2
[2020-05-05 21:59:11,547] WARNING [celery.redirected:235] Processing: Q1-T1
[2020-05-05 21:59:11,547] WARNING [celery.redirected:235] Processing: Q1-T0
[2020-05-05 21:59:12,052] WARNING [celery.redirected:235] Processing: Q1-T2
[2020-05-05 21:59:12,053] WARNING [celery.redirected:235] Processing: Q1-T3
[2020-05-05 21:59:12,556] WARNING [celery.redirected:235] Processing: Q1-T5
[2020-05-05 21:59:12,556] WARNING [celery.redirected:235] Processing: Q1-T4
[2020-05-05 21:59:13,062] WARNING [celery.redirected:235] Processing: Q1-T6
[2020-05-05 21:59:13,063] WARNING [celery.redirected:235] Processing: Q1-T7
[2020-05-05 21:59:13,565] WARNING [celery.redirected:235] Processing: Q1-T9
[2020-05-05 21:59:13,565] WARNING [celery.redirected:235] Processing: Q1-T8
[2020-05-05 21:59:14,069] WARNING [celery.redirected:235] Processing: Q1-T10
[2020-05-05 21:59:14,069] WARNING [celery.redirected:235] Processing: Q3-T0
[2020-05-05 21:59:14,571] WARNING [celery.redirected:235] Processing: Q2-T0
[2020-05-05 21:59:14,572] WARNING [celery.redirected:235] Processing: Q2-T1
[2020-05-05 21:59:15,078] WARNING [celery.redirected:235] Processing: Q1-T11
[2020-05-05 21:59:15,078] WARNING [celery.redirected:235] Processing: Q2-T2
[2020-05-05 21:59:15,581] WARNING [celery.redirected:235] Processing: Q2-T3
[2020-05-05 21:59:15,581] WARNING [celery.redirected:235] Processing: Q1-T12
[2020-05-05 21:59:16,084] WARNING [celery.redirected:235] Processing: Q1-T13
[2020-05-05 21:59:16,084] WARNING [celery.redirected:235] Processing: Q2-T4
[2020-05-05 21:59:16,586] WARNING [celery.redirected:235] Processing: Q1-T14
[2020-05-05 21:59:16,586] WARNING [celery.redirected:235] Processing: Q2-T5
[2020-05-05 21:59:17,089] WARNING [celery.redirected:235] Processing: Q1-T15
[2020-05-05 21:59:17,089] WARNING [celery.redirected:235] Processing: Q2-T6
[2020-05-05 21:59:17,591] WARNING [celery.redirected:235] Processing: Q1-T16
[2020-05-05 21:59:17,592] WARNING [celery.redirected:235] Processing: Q2-T7
[2020-05-05 21:59:18,094] WARNING [celery.redirected:235] Processing: Q1-T17
[2020-05-05 21:59:18,094] WARNING [celery.redirected:235] Processing: Q2-T8
[2020-05-05 21:59:18,597] WARNING [celery.redirected:235] Processing: Q1-T18
[2020-05-05 21:59:18,597] WARNING [celery.redirected:235] Processing: Q2-T9
[2020-05-05 21:59:19,102] WARNING [celery.redirected:235] Processing: Q1-T19
[2020-05-05 21:59:19,102] WARNING [celery.redirected:235] Processing: Q1-T20
[2020-05-05 21:59:19,607] WARNING [celery.redirected:235] Processing: Q1-T21
[2020-05-05 21:59:19,607] WARNING [celery.redirected:235] Processing: Q1-T22
[2020-05-05 21:59:20,110] WARNING [celery.redirected:235] Processing: Q1-T23
[2020-05-05 21:59:20,110] WARNING [celery.redirected:235] Processing: Q2-T10
[2020-05-05 21:59:20,614] WARNING [celery.redirected:235] Processing: Q1-T24
[2020-05-05 21:59:20,614] WARNING [celery.redirected:235] Processing: Q2-T11
[2020-05-05 21:59:21,118] WARNING [celery.redirected:235] Processing: Q1-T25
[2020-05-05 21:59:21,118] WARNING [celery.redirected:235] Processing: Q1-T26
[2020-05-05 21:59:21,622] WARNING [celery.redirected:235] Processing: Q2-T12
[2020-05-05 21:59:21,622] WARNING [celery.redirected:235] Processing: Q1-T27
[2020-05-05 21:59:22,124] WARNING [celery.redirected:235] Processing: Q1-T28
[2020-05-05 21:59:22,124] WARNING [celery.redirected:235] Processing: Q2-T13
[2020-05-05 21:59:22,627] WARNING [celery.redirected:235] Processing: Q2-T14
[2020-05-05 21:59:22,627] WARNING [celery.redirected:235] Processing: Q1-T29
[2020-05-05 21:59:23,129] WARNING [celery.redirected:235] Processing: Q1-T31
[2020-05-05 21:59:23,129] WARNING [celery.redirected:235] Processing: Q1-T30
[2020-05-05 21:59:23,631] WARNING [celery.redirected:235] Processing: Q2-T15
[2020-05-05 21:59:23,632] WARNING [celery.redirected:235] Processing: Q1-T32
[2020-05-05 21:59:24,134] WARNING [celery.redirected:235] Processing: Q1-T33
[2020-05-05 21:59:24,134] WARNING [celery.redirected:235] Processing: Q2-T16
[2020-05-05 21:59:24,636] WARNING [celery.redirected:235] Processing: Q2-T17
[2020-05-05 21:59:24,636] WARNING [celery.redirected:235] Processing: Q2-T18
[2020-05-05 21:59:25,138] WARNING [celery.redirected:235] Processing: Q2-T19
[2020-05-05 21:59:25,139] WARNING [celery.redirected:235] Processing: Q1-T34
[2020-05-05 21:59:25,641] WARNING [celery.redirected:235] Processing: Q1-T35
[2020-05-05 21:59:25,642] WARNING [celery.redirected:235] Processing: Q2MOAR-T0
[2020-05-05 21:59:26,144] WARNING [celery.redirected:235] Processing: Q1-T36
[2020-05-05 21:59:26,144] WARNING [celery.redirected:235] Processing: Q1-T37
[2020-05-05 21:59:26,649] WARNING [celery.redirected:235] Processing: Q2MOAR-T1
[2020-05-05 21:59:26,649] WARNING [celery.redirected:235] Processing: Q1-T38
[2020-05-05 21:59:27,153] WARNING [celery.redirected:235] Processing: Q2MOAR-T2
[2020-05-05 21:59:27,154] WARNING [celery.redirected:235] Processing: Q1-T39
[2020-05-05 21:59:27,656] WARNING [celery.redirected:235] Processing: Q2MOAR-T3
[2020-05-05 21:59:27,656] WARNING [celery.redirected:235] Processing: Q2MOAR-T4
[2020-05-05 21:59:28,159] WARNING [celery.redirected:235] Processing: Q2MOAR-T5
[2020-05-05 21:59:28,160] WARNING [celery.redirected:235] Processing: Q1-T40
[2020-05-05 21:59:28,664] WARNING [celery.redirected:235] Processing: Q2MOAR-T6
[2020-05-05 21:59:28,664] WARNING [celery.redirected:235] Processing: Q1-T41
[2020-05-05 21:59:29,167] WARNING [celery.redirected:235] Processing: Q2MOAR-T7
[2020-05-05 21:59:29,167] WARNING [celery.redirected:235] Processing: Q1-T42
当芹菜以 1 的并发性运行时，也有类似的结果：
[2020-05-05 22:01:33,879] WARNING [celery.redirected:235] Processing: Q1-T0
[2020-05-05 22:01:34,385] WARNING [celery.redirected:235] Processing: Q1-T1
[2020-05-05 22:01:34,888] WARNING [celery.redirected:235] Processing: Q1-T2
[2020-05-05 22:01:35,391] WARNING [celery.redirected:235] Processing: Q1-T3
[2020-05-05 22:01:35,894] WARNING [celery.redirected:235] Processing: Q1-T4
[2020-05-05 22:01:36,397] WARNING [celery.redirected:235] Processing: Q1-T5
[2020-05-05 22:01:36,899] WARNING [celery.redirected:235] Processing: Q3-T0
[2020-05-05 22:01:37,404] WARNING [celery.redirected:235] Processing: Q2-T0
[2020-05-05 22:01:37,907] WARNING [celery.redirected:235] Processing: Q2-T1
[2020-05-05 22:01:38,411] WARNING [celery.redirected:235] Processing: Q1-T6
[2020-05-05 22:01:38,913] WARNING [celery.redirected:235] Processing: Q2-T2
[2020-05-05 22:01:39,417] WARNING [celery.redirected:235] Processing: Q2-T3
[2020-05-05 22:01:39,919] WARNING [celery.redirected:235] Processing: Q2-T4
[2020-05-05 22:01:40,422] WARNING [celery.redirected:235] Processing: Q1-T7
[2020-05-05 22:01:40,925] WARNING [celery.redirected:235] Processing: Q2-T5
[2020-05-05 22:01:41,429] WARNING [celery.redirected:235] Processing: Q1-T8