Python Queue.asyncio ValueError:task_done()调用次数太多-编码错误或检测到错误?
我实现了一段代码,从一个队列中获取一个元素,并从队列列表中将相同的对象放入每个队列中。问题是,当我运行一个特定的测试时,我得到了一个Python Queue.asyncio ValueError:task_done()调用次数太多-编码错误或检测到错误?,python,pytest,python-asyncio,python-3.7,pytest-asyncio,Python,Pytest,Python Asyncio,Python 3.7,Pytest Asyncio,我实现了一段代码,从一个队列中获取一个元素,并从队列列表中将相同的对象放入每个队列中。问题是,当我运行一个特定的测试时,我得到了一个ValueError:task_done()调用次数过多的异常。此错误发生在测试代码中,而不是正在测试的代码中 我正在使用asyncio.Queue并使用协同程序进行编程。 我匹配了每个队列。用一个队列获得。任务完成调用。 我正在用pytest测试代码 我正在使用以下LIB: Python 3.7 pytest==3.10.0 pytest asyncio==0.
ValueError:task_done()调用次数过多的异常。此错误发生在测试代码中,而不是正在测试的代码中
我正在使用asyncio.Queue
并使用协同程序进行编程。
我匹配了每个队列。用一个队列获得。任务完成调用。
我正在用pytest测试代码
我正在使用以下LIB:
- Python 3.7
- pytest==3.10.0
- pytest asyncio==0.9.0
我有两个文件:middleware.py
包含我的类实现和test\u middleware.py
实现pytest测试
文件middlware.py
:
import asyncio
class DistributorMiddleware:
def __init__(self, in_queue, out_list_queue):
self._in = in_queue
self._out = out_list_queue
async def distribute(self):
while True:
ele = await self._in.get()
count=0
for queue in self._out:
await queue.put(ele)
count+=1
print(f'inserted ele in {count}')
queue.task_done()
if ele == None:
break
for queue in self._out:
await queue.join()
import pytest
import asyncio
from asyncio import Queue
from middleware import DistributorMiddleware
import random
import os
@pytest.mark.asyncio
async def test_distribution(request, event_loop):
q_list = [ Queue() for _ in range(10) ]
_in = Queue()
distrib = DistributorMiddleware(_in, q_list)
event_loop.create_task(distrib.distribute())
num_ele = random.randint(1, 10)
ele_set = set()
for _ in range(num_ele):
ele = os.urandom(4)
ele_set.add(ele)
await _in.put(ele)
await _in.put(None)
await asyncio.sleep(1)
for i,q in enumerate(q_list):
assert q.qsize() == num_ele + 1
c_set = ele_set.copy()
count= 0
while True:
e = await q.get()
count+=1
print(f'Queue {i}: element: "{e}" number {count} extracted of {q.qsize()}!')
q.task_done()
if e == None:
break
assert e in c_set
c_set.remove(e)
文件test\u middleware.py
:
import asyncio
class DistributorMiddleware:
def __init__(self, in_queue, out_list_queue):
self._in = in_queue
self._out = out_list_queue
async def distribute(self):
while True:
ele = await self._in.get()
count=0
for queue in self._out:
await queue.put(ele)
count+=1
print(f'inserted ele in {count}')
queue.task_done()
if ele == None:
break
for queue in self._out:
await queue.join()
import pytest
import asyncio
from asyncio import Queue
from middleware import DistributorMiddleware
import random
import os
@pytest.mark.asyncio
async def test_distribution(request, event_loop):
q_list = [ Queue() for _ in range(10) ]
_in = Queue()
distrib = DistributorMiddleware(_in, q_list)
event_loop.create_task(distrib.distribute())
num_ele = random.randint(1, 10)
ele_set = set()
for _ in range(num_ele):
ele = os.urandom(4)
ele_set.add(ele)
await _in.put(ele)
await _in.put(None)
await asyncio.sleep(1)
for i,q in enumerate(q_list):
assert q.qsize() == num_ele + 1
c_set = ele_set.copy()
count= 0
while True:
e = await q.get()
count+=1
print(f'Queue {i}: element: "{e}" number {count} extracted of {q.qsize()}!')
q.task_done()
if e == None:
break
assert e in c_set
c_set.remove(e)
在测试中,中间件应该从输入队列中获取元素,并将它们从列表中放入10个队列中。它正确地完成了工作
测试代码从10个队列中的每个队列中获取所有元素,并检查它们是否存在于原始队列中。对于前9个队列,一切正常,没有错误,但是当测试尝试从第十个列表中获取第一个元素时,会引发ValueError
:
request = <FixtureRequest for <Function 'test_distribution'>>, event_loop = <_UnixSelectorEventLoop running=False closed=False debug=False>
@pytest.mark.asyncio
async def test_distribution(request, event_loop):
q_list = [ Queue() for _ in range(10) ]
_in = Queue()
distrib = DistributorMiddleware(_in, q_list)
event_loop.create_task(distrib.distribute())
num_ele = random.randint(1, 10)
ele_set = set()
for _ in range(num_ele):
ele = os.urandom(4)
ele_set.add(ele)
await _in.put(ele)
await _in.put(None)
await asyncio.sleep(1)
for i,q in enumerate(q_list):
assert q.qsize() == num_ele + 1
c_set = ele_set.copy()
count= 0
while True:
e = await q.get()
count+=1
print(f'Queue {i}: element: "{e}" number {count} extracted of {q.qsize()}!')
> q.task_done()
test_middlewares.py:34:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = <Queue at 0x7f7af5b9d828 maxsize=0 _queue=[b'\x15\xad\t\xaf', b'\x8b\xa2M=', None]>
def task_done(self):
"""Indicate that a formerly enqueued task is complete.
Used by queue consumers. For each get() used to fetch a task,
a subsequent call to task_done() tells the queue that the processing
on the task is complete.
If a join() is currently blocking, it will resume when all items have
been processed (meaning that a task_done() call was received for every
item that had been put() into the queue).
Raises ValueError if called more times than there were items placed in
the queue.
"""
if self._unfinished_tasks <= 0:
> raise ValueError('task_done() called too many times')
E ValueError: task_done() called too many times
/usr/lib/python3.7/asyncio/queues.py:202: ValueError
这样做,我可以看到,即使有许多ValueError
被抛出,元素仍会不断从队列中检索。测试成功:
platform linux -- Python 3.7.1, pytest-3.10.0, py-1.7.0, pluggy-0.8.0
rootdir: /tmp/stack, inifile:
plugins: asyncio-0.9.0
collected 1 item
test_middlewares.py . [100%]
============================================================================================ 1 passed in 1.04 seconds =============================================================================================
为了确保测试正在使用所有列表中的所有元素,我在测试结束时添加了一个错误断言:
assert e in c_set
c_set.remove(e)
+ assert False == True
+
结果输出显示从所有列表检索所有元素,但在最后一个队列上完成的每个任务都会生成一个ValueError
Queue 7: element: "b'\x9b\xf8m\x02'" number 1 extracted of 3!
Queue 7: element: "b'\x15\xad\t\xaf'" number 2 extracted of 2!
Queue 7: element: "b'\x8b\xa2M='" number 3 extracted of 1!
Queue 7: element: "None" number 4 extracted of 0!
Queue 8: element: "b'\x9b\xf8m\x02'" number 1 extracted of 3!
Queue 8: element: "b'\x15\xad\t\xaf'" number 2 extracted of 2!
Queue 8: element: "b'\x8b\xa2M='" number 3 extracted of 1!
Queue 8: element: "None" number 4 extracted of 0!
Queue 9: element: "b'\x9b\xf8m\x02'" number 1 extracted of 3!
============================================================================================ 1 failed in 1.06 seconds ==
问题是,我是否遗漏了什么,代码中有错误,或者我发现了一个bug?您的代码中有错误。实际上,queue.task_done()
但是您的中间件类正在它刚刚使用的队列上调用它。.put()
,用于self.\u out
列表中的最后一个队列;从DistributorMiddleware.distribute()中删除队列.task_done()
调用:
当删除该行时,测试通过
您在测试中看到引发异常的原因是,只有到那时队列才知道task\u done()
调用得太频繁。DistributorMiddleware.distribute()
中的queue.task_done()
调用将未完成的任务计数器递减1,但只有当该计数器降至零以下时,才能检测到异常。只有在test_distribution()
中将最后一个任务从队列中取出时,才能到达该点,此时未完成的任务计数器至少提前一步到达0
也许这是为了调用self.\u in.task\u done()
?您只是在循环中从该队列中获取了一个元素:
async def distribute(self):
while True:
ele = await self._in.get()
# getting an element from self._in
count=0
for queue in self._out:
await queue.put(ele)
count+=1
print(f'inserted ele in {count}')
self._in.task_done()
# done with ele, so decrement the self._in unfinished tasks counter
旁注:不要使用==None
,它是一个单例,因此测试它的python方法是使用是None
。这正是问题所在。当我想在
中使用self.\u时,我使用了queue
。非常感谢。