Function rwlock

dvc/rwlock.py:188–221

Create non-thread-safe RWLock for file paths. Args: tmp_dir (str): existing directory where to create the rwlock file. fs (FileSystem): fs instance that tmp_dir belongs to. cmd (str): command that will be working on these file path. read ([str]): file paths that

(tmp_dir, fs, cmd, read, write, hardlink)

@contextmanager
def rwlock(tmp_dir, fs, cmd, read, write, hardlink):
    """Create non-thread-safe RWLock for file paths.

    Args:
        tmp_dir (str): existing directory where to create the rwlock file.
        fs (FileSystem): fs instance that tmp_dir belongs to.
        cmd (str): command that will be working on these file path.
        read ([str]): file paths that are going to be read.
        write ([str]): file paths that are going to be written.
        hardlink (bool): use hardlink lock to guard rwlock file when on edit.

    Raises:
        LockError: raised if file paths we want to read is being written to by
            another command or if file paths we want to write is being written
            to or read from by another command.
        RWLockFileCorruptedError: raised if rwlock file is not a valid JSON.
        RWLockFileFormatError: raised if rwlock file is a valid JSON, but
            has internal format that doesn't pass our schema validation.
    """
    info = {"pid": os.getpid(), "cmd": cmd}

    with _edit_rwlock(tmp_dir, fs, hardlink) as lock:
        _check_blockers(tmp_dir, lock, info, mode="write", waiters=read + write)
        _check_blockers(tmp_dir, lock, info, mode="read", waiters=write)

        rchanges = _acquire_read(lock, info, read)
        wchanges = _acquire_write(lock, info, write)

    try:
        yield
    finally:
        with _edit_rwlock(tmp_dir, fs, hardlink) as lock:
            _release_write(lock, info, wchanges)
            _release_read(lock, info, rchanges)