148 lines
5.1 KiB
Python
148 lines
5.1 KiB
Python
# Copyright 2017 Google Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Common utilities for Google Media Downloads and Resumable Uploads.
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Includes custom exception types, useful constants and shared helpers.
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"""
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_SLEEP_RETRY_ERROR_MSG = (
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u"At most one of `max_cumulative_retry` and `max_retries` " u"can be specified."
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)
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UPLOAD_CHUNK_SIZE = 262144 # 256 * 1024
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"""int: Chunks in a resumable upload must come in multiples of 256 KB."""
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PERMANENT_REDIRECT = 308
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"""int: Permanent redirect status code.
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It is used by Google services to indicate some (but not all) of
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a resumable upload has been completed.
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``http.client.PERMANENT_REDIRECT`` was added in Python 3.5, so
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can't be used in a "general" code base.
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For more information, see `RFC 7238`_.
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.. _RFC 7238: https://tools.ietf.org/html/rfc7238
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"""
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TOO_MANY_REQUESTS = 429
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"""int: Status code indicating rate-limiting.
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``http.client.TOO_MANY_REQUESTS`` was added in Python 3.3, so
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can't be used in a "general" code base.
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For more information, see `RFC 6585`_.
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.. _RFC 6585: https://tools.ietf.org/html/rfc6585#section-4
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"""
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MAX_SLEEP = 64.0
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"""float: Maximum amount of time allowed between requests.
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Used during the retry process for sleep after a failed request.
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Chosen since it is the power of two nearest to one minute.
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"""
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MAX_CUMULATIVE_RETRY = 600.0
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"""float: Maximum total sleep time allowed during retry process.
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This is provided (10 minutes) as a default. When the cumulative sleep
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exceeds this limit, no more retries will occur.
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"""
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class InvalidResponse(Exception):
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"""Error class for responses which are not in the correct state.
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Args:
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response (object): The HTTP response which caused the failure.
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args (tuple): The positional arguments typically passed to an
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exception class.
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"""
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def __init__(self, response, *args):
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super(InvalidResponse, self).__init__(*args)
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self.response = response
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"""object: The HTTP response object that caused the failure."""
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class DataCorruption(Exception):
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"""Error class for corrupt media transfers.
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Args:
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response (object): The HTTP response which caused the failure.
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args (tuple): The positional arguments typically passed to an
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exception class.
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"""
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def __init__(self, response, *args):
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super(DataCorruption, self).__init__(*args)
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self.response = response
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"""object: The HTTP response object that caused the failure."""
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class RetryStrategy(object):
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"""Configuration class for retrying failed requests.
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At most one of ``max_cumulative_retry`` and ``max_retries`` can be
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specified (they are both caps on the total number of retries). If
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neither are specified, then ``max_cumulative_retry`` is set as
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:data:`MAX_CUMULATIVE_RETRY`.
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Args:
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max_sleep (Optional[float]): The maximum amount of time to sleep after
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a failed request. Default is :attr:`MAX_SLEEP`.
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max_cumulative_retry (Optional[float]): The maximum **total** amount of
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time to sleep during retry process.
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max_retries (Optional[int]): The number of retries to attempt.
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Attributes:
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max_sleep (float): Maximum amount of time allowed between requests.
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max_cumulative_retry (Optional[float]): Maximum total sleep time
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allowed during retry process.
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max_retries (Optional[int]): The number retries to attempt.
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Raises:
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ValueError: If both of ``max_cumulative_retry`` and ``max_retries``
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are passed.
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"""
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def __init__(
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self, max_sleep=MAX_SLEEP, max_cumulative_retry=None, max_retries=None
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):
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if max_cumulative_retry is not None and max_retries is not None:
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raise ValueError(_SLEEP_RETRY_ERROR_MSG)
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if max_cumulative_retry is None and max_retries is None:
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max_cumulative_retry = MAX_CUMULATIVE_RETRY
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self.max_sleep = max_sleep
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self.max_cumulative_retry = max_cumulative_retry
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self.max_retries = max_retries
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def retry_allowed(self, total_sleep, num_retries):
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"""Check if another retry is allowed.
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Args:
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total_sleep (float): The amount of sleep accumulated by the caller.
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num_retries (int): The number of retries already attempted by
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the caller.
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Returns:
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bool: Indicating if another retry is allowed (depending on either
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the cumulative sleep allowed or the maximum number of retries
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allowed.
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"""
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if self.max_cumulative_retry is None:
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return num_retries <= self.max_retries
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else:
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return total_sleep <= self.max_cumulative_retry
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