多处理导致 Python 崩溃，并在调用 fork() 时给出一个错误可能已经在另一个线程中进行 [英] Multiprocessing causes Python to crash and gives an error may have been in progress in another thread when fork() was called

问题描述

我对 Python 比较陌生，正在尝试为我的 for 循环实现一个多处理模块.

I am relatively new to Python and trying to implement a Multiprocessing module for my for loop.

我在 img_urls 中存储了一组图像 url，我需要下载并应用一些 Google 视觉.

I have an array of Image url's stored in img_urls which I need to download and apply some Google vision.

if __name__ == '__main__':

    img_urls = [ALL_MY_Image_URLS]
    runAll(img_urls)
    print("--- %s seconds ---" % (time.time() - start_time)) 

这是我的 runAll() 方法

This is my runAll() method

def runAll(img_urls):
    num_cores = multiprocessing.cpu_count()

    print("Image URLS  {}",len(img_urls))
    if len(img_urls) > 2:
        numberOfImages = 0
    else:
        numberOfImages = 1

    start_timeProcess = time.time()

    pool = multiprocessing.Pool()
    pool.map(annotate,img_urls)
    end_timeProcess = time.time()
    print('
 Time to complete ', end_timeProcess-start_timeProcess)

    print(full_matching_pages)


def annotate(img_path):
    file =  requests.get(img_path).content
    print("file is",file)
    """Returns web annotations given the path to an image."""
    print('Process Working under ',os.getpid())
    image = types.Image(content=file)
    web_detection = vision_client.web_detection(image=image).web_detection
    report(web_detection)

当我运行它并且python崩溃时，我收到了这个警告

I am getting this as the warning when I run it and python crashes

objc[67570]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[67570]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[67567]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[67567]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[67568]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[67568]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[67569]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[67569]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[67571]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[67571]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.
objc[67572]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called.
objc[67572]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug.

推荐答案

出现此错误是因为在 macOS High Sierra 和更高版本的 macOS 中增加了限制多线程的安全性.我知道这个答案有点晚了，但我使用以下方法解决了问题:

This error occurs because of added security to restrict multithreading in macOS High Sierra and later versions of macOS. I know this answer is a bit late, but I solved the problem using the following method:

设置环境变量 .bash_profile(或 .zshrc 对于最近的 macOS)以允许多线程应用程序或脚本在新的 macOS High Sierra 安全规则下.

Set an environment variable .bash_profile (or .zshrc for recent macOS) to allow multithreading applications or scripts under the new macOS High Sierra security rules.

打开终端:

$ nano .bash_profile

将以下行添加到文件末尾:

Add the following line to the end of the file:

OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

保存、退出、关闭终端并重新打开终端.检查环境变量现在是否已设置:

Save, exit, close terminal and re-open the terminal. Check to see that the environment variable is now set:

$ env

您将看到类似于以下内容的输出:

You will see output similar to:

TERM_PROGRAM=Apple_Terminal
SHELL=/bin/bash
TERM=xterm-256color
TMPDIR=/var/folders/pn/vasdlj3ojO#OOas4dasdffJq/T/
Apple_PubSub_Socket_Render=/private/tmp/com.apple.launchd.E7qLFJDSo/Render
TERM_PROGRAM_VERSION=404
TERM_SESSION_ID=NONE
OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

您现在应该可以使用多线程运行 Python 脚本了.

You should now be able to run your Python script with multithreading.

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