Description
Using the format context manager in a threaded environment introduces a race condition where the global formatter and global plural flag can be reset by one context manager after another context manager has set it, and before it has formatted a string within that context.
A solution to this is bitmath should either make sure that the context manager is threadsafe, or warn in the documentation that the context manager isn't threadsafe and that a user should use the Bitmath object's format function directly instead.
How to REPRODUCE the issue:
This test case can reproduce the issue. The test is only checking format_string but a similar method could be used to test format_plural
#! /usr/bin/env python
from __future__ import print_function
import random
import queue
import threading
import time
import unittest
import bitmath
default_format = bitmath.format_string
bitmath.format_string = "{not_in_context_manager}"
THREAD_COUNT = 8
def format_string(event, err_queue):
size = bitmath.KiB(0)
try:
with bitmath.format(fmt_str=default_format):
event.wait()
time.sleep(random.random() * 2)
str(size)
except Exception as e:
err_queue.put(e)
class TestThreading(unittest.TestCase):
def test_context_manager(self):
event = threading.Event()
err_queue = queue.Queue()
threads = []
for i in xrange(THREAD_COUNT):
threads.append(threading.Thread(target=format_string, args=(event, err_queue)))
for thread in threads:
thread.start()
time.sleep(1)
event.set()
for thread in threads:
thread.join()
error = err_queue.get()
if error:
raise error
if __name__ == '__main__':
unittest.main()And will produce the following error
======================================================================
ERROR: test_context_manager (__main__.TestThreading)
----------------------------------------------------------------------
Traceback (most recent call last):
File "./test_threading.py", line 47, in test_context_manager
raise error
KeyError: 'not_in_context_manager'
How REPRODUCIBLE (every time? intermittently? only in certain environments?):
In general the the error would only happen in threaded environments where there is a requirement to override the default formatter using the context manager. In our case it was happening intermittently when testing a threaded part of our application which was logging the size of bitmath objects
What you EXPECTED to happen:
For strings to be successfully formatted with the provided formatter to the context
What ACTUALLY happened:
Some sizes where formatted with the formatter of another context.
VERSION of bitmath effected:
- Version: 1.3.1.1
- Install Source: PyPi
Your OPERATING SYSTEM and the affected PYTHON VERSION:
unbuntu16.04 and python 2.7.14