9c55acd286
Instead of retrying HTTP requests only for 429 status code by default, prefer to use the generic retry policy enabling to also retry for status codes >= 500 but also on ConnectionError exceptions. Rename throttling_retry decorator to http_retry to reflect this change.
113 lines
3.7 KiB
Python
113 lines
3.7 KiB
Python
# Copyright (C) 2018-2022 the Software Heritage developers
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# License: GNU General Public License version 3, or any later version
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# See top-level LICENSE file for more information
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from typing import Callable, Iterator, Tuple
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from requests.exceptions import ConnectionError, HTTPError
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from requests.status_codes import codes
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from tenacity import retry as tenacity_retry
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from tenacity.stop import stop_after_attempt
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from tenacity.wait import wait_exponential
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def split_range(total_pages: int, nb_pages: int) -> Iterator[Tuple[int, int]]:
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"""Split `total_pages` into mostly `nb_pages` ranges. In some cases, the last range can
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have one more element.
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>>> list(split_range(19, 10))
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[(0, 9), (10, 19)]
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>>> list(split_range(20, 3))
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[(0, 2), (3, 5), (6, 8), (9, 11), (12, 14), (15, 17), (18, 20)]
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>>> list(split_range(21, 3))
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[(0, 2), (3, 5), (6, 8), (9, 11), (12, 14), (15, 17), (18, 21)]
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"""
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prev_index = None
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for index in range(0, total_pages, nb_pages):
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if index is not None and prev_index is not None:
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yield prev_index, index - 1
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prev_index = index
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if index != total_pages:
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yield index, total_pages
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def is_throttling_exception(e: Exception) -> bool:
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"""
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Checks if an exception is a requests.exception.HTTPError for
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a response with status code 429 (too many requests).
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"""
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return (
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isinstance(e, HTTPError) and e.response.status_code == codes.too_many_requests
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)
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def is_retryable_exception(e: Exception) -> bool:
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"""
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Checks if an exception is worth retrying (connection, throttling or a server error).
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"""
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is_connection_error = isinstance(e, ConnectionError)
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is_500_error = isinstance(e, HTTPError) and e.response.status_code >= 500
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return is_connection_error or is_throttling_exception(e) or is_500_error
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def retry_if_exception(retry_state, predicate: Callable[[Exception], bool]) -> bool:
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"""
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Custom tenacity retry predicate for handling exceptions with the given predicate.
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"""
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attempt = retry_state.outcome
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if attempt.failed:
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exception = attempt.exception()
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return predicate(exception)
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return False
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def retry_policy_generic(retry_state) -> bool:
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"""
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Custom tenacity retry predicate for handling failed requests:
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- ConnectionError
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- Server errors (status >= 500)
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- Throttling errors (status == 429)
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This does not handle 404, 403 or other status codes.
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"""
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return retry_if_exception(retry_state, is_retryable_exception)
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WAIT_EXP_BASE = 10
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MAX_NUMBER_ATTEMPTS = 5
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def http_retry(
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retry=retry_policy_generic,
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wait=wait_exponential(exp_base=WAIT_EXP_BASE),
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stop=stop_after_attempt(max_attempt_number=MAX_NUMBER_ATTEMPTS),
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**retry_args,
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):
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"""
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Decorator based on `tenacity` for retrying a function possibly raising
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requests.exception.HTTPError for status code 429 (too many requests).
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It provides a default configuration that should work properly in most
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cases but all `tenacity.retry` parameters can also be overridden in client
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code.
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When the mmaximum of attempts is reached, the HTTPError exception will then
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be reraised.
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Args:
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retry: function defining request retry condition (default to 429 status code)
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https://tenacity.readthedocs.io/en/latest/#whether-to-retry
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wait: function defining wait strategy before retrying (default to exponential
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backoff) https://tenacity.readthedocs.io/en/latest/#waiting-before-retrying
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stop: function defining when to stop retrying (default after 5 attempts)
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https://tenacity.readthedocs.io/en/latest/#stopping
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"""
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return tenacity_retry(retry=retry, wait=wait, stop=stop, reraise=True, **retry_args)
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