使用 boto3 将本地文件夹同步到 s3 存储桶

Question

我注意到 boto3 中没有可通过命令行执行的“同步”操作的 API。

所以，

如何使用 boto3 将本地文件夹同步到给定的存储桶？

Answer 1

我刚刚为这个问题实现了一个简单的类。我把它贴在这里希望它可以帮助任何有同样问题的人。

您可以修改 S3Sync.sync 以将文件大小考虑在内。

class S3Sync:
    """
    Class that holds the operations needed for synchronize local dirs to a given bucket.
    """

    def __init__(self):
        self._s3 = boto3.client('s3')

    def sync(self, source: str, dest: str) -> [str]:
        """
        Sync source to dest, this means that all elements existing in
        source that not exists in dest will be copied to dest.

        No element will be deleted.

        :param source: Source folder.
        :param dest: Destination folder.

        :return: None
        """

        paths = self.list_source_objects(source_folder=source)
        objects = self.list_bucket_objects(dest)

        # Getting the keys and ordering to perform binary search
        # each time we want to check if any paths is already there.
        object_keys = [obj['Key'] for obj in objects]
        object_keys.sort()
        object_keys_length = len(object_keys)
        
        for path in paths:
            # Binary search.
            index = bisect_left(object_keys, path)
            if index == object_keys_length:
                # If path not found in object_keys, it has to be sync-ed.
                self._s3.upload_file(str(Path(source).joinpath(path)),  Bucket=dest, Key=path)

    def list_bucket_objects(self, bucket: str) -> [dict]:
        """
        List all objects for the given bucket.

        :param bucket: Bucket name.
        :return: A [dict] containing the elements in the bucket.

        Example of a single object.

        {
            'Key': 'example/example.txt',
            'LastModified': datetime.datetime(2019, 7, 4, 13, 50, 34, 893000, tzinfo=tzutc()),
            'ETag': '"b11564415be7f58435013b414a59ae5c"',
            'Size': 115280,
            'StorageClass': 'STANDARD',
            'Owner': {
                'DisplayName': 'webfile',
                'ID': '75aa57f09aa0c8caeab4f8c24e99d10f8e7faeebf76c078efc7c6caea54ba06a'
            }
        }

        """
        try:
            contents = self._s3.list_objects(Bucket=bucket)['Contents']
        except KeyError:
            # No Contents Key, empty bucket.
            return []
        else:
            return contents

    @staticmethod
    def list_source_objects(source_folder: str) -> [str]:
        """
        :param source_folder:  Root folder for resources you want to list.
        :return: A [str] containing relative names of the files.

        Example:

            /tmp
                - example
                    - file_1.txt
                    - some_folder
                        - file_2.txt

            >>> sync.list_source_objects("/tmp/example")
            ['file_1.txt', 'some_folder/file_2.txt']

        """

        path = Path(source_folder)

        paths = []

        for file_path in path.rglob("*"):
            if file_path.is_dir():
                continue
            str_file_path = str(file_path)
            str_file_path = str_file_path.replace(f'{str(path)}/', "")
            paths.append(str_file_path)

        return paths


if __name__ == '__main__':
    sync = S3Sync()
    sync.sync("/temp/some_folder", "some_bucket_name")

更新：

@Z.Wei 评论：

深入研究一下以处理奇怪的 bisect 函数。我们可以使用 if path not in object_keys:?

我认为这是一个有趣的问题，值得更新答案，不要迷失在评论中。

回答：

不，if path not in object_keys将执行线性搜索O(n)。bisect_* 执行二进制搜索（列表必须排序），其为 O(log(n))。

大多数情况下，您将处理足够多的对象来进行排序和二进制搜索，这通常比仅使用 in 关键字更快。

考虑到您必须使用in O(m * n)检查源中的每条路径与目标中的每条路径，其中 m 是源中的对象数，而 n 是目标中的对象数。使用 bisect 整个事情是O( n * log(n) )

但 ...

如果我考虑一下，您可以使用集合使算法更快（并且简单，因此更具有 Python 风格）：

def sync(self, source: str, dest: str) -> [str]:

    # Local paths
    paths = set(self.list_source_objects(source_folder=source))

    # Getting the keys (remote s3 paths).
    objects = self.list_bucket_objects(dest)
    object_keys = set([obj['Key'] for obj in objects])

    # Compute the set difference: What we have in paths that does
    # not exists in object_keys.
    to_sync = paths - object_keys

    sournce_path = Path(source)
    for path in to_sync:
        self._s3.upload_file(str(sournce_path / path),
                                Bucket=dest, Key=path)

搜索在sets为O（1），因此，使用一套整个事情将是O（n）的方式更快，以前的O（M *的log（n）） 。

进一步改进

代码可以改进更多的方法list_bucket_objects并list_source_objects返回集合而不是列表。