open_with_lock

open_with_lock(filename: str, mode: str = 'r', *args: Any, **kwargs: Any) → Iterator[TextIOWrapper][source]

Open a file with an exclusive lock.

This context manager attempts to acquire an exclusive lock on the file upon opening. Other processes using open_with_lock will wait until the lock is automatically released when exiting the context.

Parameters:

  • filename -- Path to the file to open and lock.

  • mode -- File open mode (e.g., 'rt', 'wt', 'a', 'rb').

  • *args -- Additional positional arguments to the built-in open() function.

  • **kwargs -- Additional keyword arguments to the built-in open() function.

Yields:

The opened file object with an exclusive lock acquired (if supported by the filesystem).

Notes

All file open calls with open_with_lock will block other open_with_lock usages (even from different processes/Lustre clients) from read/write until the lock is released. However, this locking/blocking mechanism does not prevent file access (which could potentially cause IO errors) from other file openers (e.g., the built-in open() function).

Filesystem Support: The Python fcntl API's behavior depends on the underlying OS/storage implementation: https://docs.python.org/3/library/fcntl.html. Not all OS/file systems fully support file locking. - Lustre: Requires mount option -o flock. Check with: mount -l | grep lustre

e.g. : 192.168.1.30@o2ib:/aoclst03 on /.lustre/aoc type lustre (rw,flock,user_xattr,lazystatfs)

  • NFS: Support varies by configuration (see PIPE-2051 for details)

  • Local filesystems: Generally well-supported on Unix-like systems

Testing Lock Behavior: To verify exclusive locking works on your system, run this from multiple processes:

```python import fcntl with open(filename, 'w') as fd:

fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB) # Should block/fail on second process

```