如何在Linux中的python进程之间锁定目录? [英] How to lock a directory between python processes in linux?

问题描述

我有两个(或多个)正在运行的python进程，并希望创建类似于排除互斥锁获取共享资源.在这种情况下，共享资源"是一个目录.我如何最容易/标准/等地实现互斥锁?每个进程都同意检查的隐藏.lock文件，如果存在，则将其PID添加为新行，然后在他们有权访问该文件时弹出其PID?

I have two (or more) python processes running and want to create a concept similar to an exclusion mutex for a shared resource. The 'shared resource' in this case is a directory. How might I most easily/standardly/etc implement a mutex? A hidden .lock file that each process agrees to check and, if exists, appends their PID as a new row and then pops their PID when they have access to the file?

我基本上只想清除目录，并确保在清除目录时没有其他进程尝试读取或写入该目录.

I basically just want to clear a directory and make sure no other process tries to read or write to it while I'm clearing it.

是否有标准的linux方式来做到这一点?也许我可以用python的shell行执行某些事情?

Is there a standard linux way of doing this? Maybe something I can just execute with a shell line from python?

推荐答案

Linux

Linux中有两种标准的锁定类型:强制锁定(特定于Linux).

There are two standard types of locking in Linux: advisory locking (specified in POSIX) and mandatory locking (Linux-specific).

但是，它们两者都只能应用于文件，而不能应用于目录.所以是的，您需要一个锁定文件.它假定所有用户在访问目录之前都应该了解该锁文件并获取该锁.因此，强制锁定在这里无济于事，您需要咨询性锁定.

However, both of them may be applied only on files, but not directories. So yes, you need a lock-file. It assumes that all users should know about the lock-file and acquire the lock before accessing directory. Hence, mandatory locking will not help here, and you need advisory locking.

Linux中有三种咨询文件锁:

There are three kinds of advisory file locks in Linux:

• flock(2) (在POSIX中指定)；
• POSIX记录锁定，请参见 fcntl(2) 以及 lockf(3) 包装器(均在POSIX中指定)；
• 打开文件描述锁，请参见 fcntl(2) (特定于Linux，在最近的内核中可用).

Python

在Python中，可以通过flock()，lockf()和fcntl()函数. > fcntl 模块.还有 flock 模块，它为fcntl.flock函数添加了上下文管理器支持.

In Python, flock(), lockf() and fcntl() functions are available through fcntl module. There is also flock module that adds context-manager support to fcntl.flock function.

这里是一个例子:

import flock

with open('/my/dir/lockfile', 'w') as fp:
    with flock.Flock(fp, flock.LOCK_EX) as lock:
        pass # exclusive lock is acquired here

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PS.

使用这种方法，如果它不知道您的锁定文件，则不能阻止随机进程访问您的目录.可能可以使用 FUSE 实现文件系统，该系统将支持强制性目录锁定，但是我我不知道这样的实现.

With this approach, you can not prevent a random process from accessing your directory, if it don't know about your lock-file. It is probably possible to implement a filesystem using FUSE that will support mandatory directory locks, but I'm not aware of such implementations.

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