530 lines
18 KiB
Python
530 lines
18 KiB
Python
from __future__ import annotations
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import email
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import logging
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import random
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import re
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import time
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import typing
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from itertools import takewhile
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from types import TracebackType
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from ..exceptions import (
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ConnectTimeoutError,
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InvalidHeader,
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MaxRetryError,
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ProtocolError,
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ProxyError,
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ReadTimeoutError,
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ResponseError,
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)
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from .util import reraise
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if typing.TYPE_CHECKING:
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from ..connectionpool import ConnectionPool
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from ..response import BaseHTTPResponse
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log = logging.getLogger(__name__)
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# Data structure for representing the metadata of requests that result in a retry.
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class RequestHistory(typing.NamedTuple):
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method: str | None
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url: str | None
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error: Exception | None
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status: int | None
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redirect_location: str | None
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class Retry:
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"""Retry configuration.
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Each retry attempt will create a new Retry object with updated values, so
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they can be safely reused.
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Retries can be defined as a default for a pool:
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.. code-block:: python
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retries = Retry(connect=5, read=2, redirect=5)
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http = PoolManager(retries=retries)
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response = http.request("GET", "https://example.com/")
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Or per-request (which overrides the default for the pool):
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.. code-block:: python
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response = http.request("GET", "https://example.com/", retries=Retry(10))
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Retries can be disabled by passing ``False``:
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.. code-block:: python
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response = http.request("GET", "https://example.com/", retries=False)
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Errors will be wrapped in :class:`~urllib3.exceptions.MaxRetryError` unless
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retries are disabled, in which case the causing exception will be raised.
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:param int total:
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Total number of retries to allow. Takes precedence over other counts.
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Set to ``None`` to remove this constraint and fall back on other
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counts.
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Set to ``0`` to fail on the first retry.
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Set to ``False`` to disable and imply ``raise_on_redirect=False``.
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:param int connect:
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How many connection-related errors to retry on.
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These are errors raised before the request is sent to the remote server,
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which we assume has not triggered the server to process the request.
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Set to ``0`` to fail on the first retry of this type.
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:param int read:
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How many times to retry on read errors.
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These errors are raised after the request was sent to the server, so the
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request may have side-effects.
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Set to ``0`` to fail on the first retry of this type.
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:param int redirect:
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How many redirects to perform. Limit this to avoid infinite redirect
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loops.
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A redirect is a HTTP response with a status code 301, 302, 303, 307 or
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308.
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Set to ``0`` to fail on the first retry of this type.
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Set to ``False`` to disable and imply ``raise_on_redirect=False``.
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:param int status:
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How many times to retry on bad status codes.
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These are retries made on responses, where status code matches
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``status_forcelist``.
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Set to ``0`` to fail on the first retry of this type.
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:param int other:
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How many times to retry on other errors.
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Other errors are errors that are not connect, read, redirect or status errors.
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These errors might be raised after the request was sent to the server, so the
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request might have side-effects.
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Set to ``0`` to fail on the first retry of this type.
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If ``total`` is not set, it's a good idea to set this to 0 to account
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for unexpected edge cases and avoid infinite retry loops.
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:param Collection allowed_methods:
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Set of uppercased HTTP method verbs that we should retry on.
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By default, we only retry on methods which are considered to be
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idempotent (multiple requests with the same parameters end with the
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same state). See :attr:`Retry.DEFAULT_ALLOWED_METHODS`.
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Set to a ``None`` value to retry on any verb.
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:param Collection status_forcelist:
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A set of integer HTTP status codes that we should force a retry on.
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A retry is initiated if the request method is in ``allowed_methods``
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and the response status code is in ``status_forcelist``.
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By default, this is disabled with ``None``.
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:param float backoff_factor:
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A backoff factor to apply between attempts after the second try
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(most errors are resolved immediately by a second try without a
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delay). urllib3 will sleep for::
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{backoff factor} * (2 ** ({number of previous retries}))
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seconds. If `backoff_jitter` is non-zero, this sleep is extended by::
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random.uniform(0, {backoff jitter})
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seconds. For example, if the backoff_factor is 0.1, then :func:`Retry.sleep` will
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sleep for [0.0s, 0.2s, 0.4s, 0.8s, ...] between retries. No backoff will ever
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be longer than `backoff_max`.
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By default, backoff is disabled (factor set to 0).
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:param bool raise_on_redirect: Whether, if the number of redirects is
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exhausted, to raise a MaxRetryError, or to return a response with a
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response code in the 3xx range.
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:param bool raise_on_status: Similar meaning to ``raise_on_redirect``:
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whether we should raise an exception, or return a response,
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if status falls in ``status_forcelist`` range and retries have
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been exhausted.
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:param tuple history: The history of the request encountered during
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each call to :meth:`~Retry.increment`. The list is in the order
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the requests occurred. Each list item is of class :class:`RequestHistory`.
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:param bool respect_retry_after_header:
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Whether to respect Retry-After header on status codes defined as
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:attr:`Retry.RETRY_AFTER_STATUS_CODES` or not.
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:param Collection remove_headers_on_redirect:
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Sequence of headers to remove from the request when a response
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indicating a redirect is returned before firing off the redirected
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request.
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"""
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#: Default methods to be used for ``allowed_methods``
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DEFAULT_ALLOWED_METHODS = frozenset(
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["HEAD", "GET", "PUT", "DELETE", "OPTIONS", "TRACE"]
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)
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#: Default status codes to be used for ``status_forcelist``
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RETRY_AFTER_STATUS_CODES = frozenset([413, 429, 503])
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#: Default headers to be used for ``remove_headers_on_redirect``
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DEFAULT_REMOVE_HEADERS_ON_REDIRECT = frozenset(["Cookie", "Authorization"])
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#: Default maximum backoff time.
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DEFAULT_BACKOFF_MAX = 120
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# Backward compatibility; assigned outside of the class.
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DEFAULT: typing.ClassVar[Retry]
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def __init__(
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self,
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total: bool | int | None = 10,
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connect: int | None = None,
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read: int | None = None,
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redirect: bool | int | None = None,
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status: int | None = None,
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other: int | None = None,
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allowed_methods: typing.Collection[str] | None = DEFAULT_ALLOWED_METHODS,
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status_forcelist: typing.Collection[int] | None = None,
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backoff_factor: float = 0,
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backoff_max: float = DEFAULT_BACKOFF_MAX,
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raise_on_redirect: bool = True,
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raise_on_status: bool = True,
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history: tuple[RequestHistory, ...] | None = None,
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respect_retry_after_header: bool = True,
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remove_headers_on_redirect: typing.Collection[
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str
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] = DEFAULT_REMOVE_HEADERS_ON_REDIRECT,
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backoff_jitter: float = 0.0,
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) -> None:
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self.total = total
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self.connect = connect
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self.read = read
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self.status = status
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self.other = other
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if redirect is False or total is False:
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redirect = 0
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raise_on_redirect = False
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self.redirect = redirect
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self.status_forcelist = status_forcelist or set()
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self.allowed_methods = allowed_methods
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self.backoff_factor = backoff_factor
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self.backoff_max = backoff_max
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self.raise_on_redirect = raise_on_redirect
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self.raise_on_status = raise_on_status
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self.history = history or ()
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self.respect_retry_after_header = respect_retry_after_header
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self.remove_headers_on_redirect = frozenset(
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h.lower() for h in remove_headers_on_redirect
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)
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self.backoff_jitter = backoff_jitter
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def new(self, **kw: typing.Any) -> Retry:
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params = dict(
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total=self.total,
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connect=self.connect,
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read=self.read,
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redirect=self.redirect,
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status=self.status,
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other=self.other,
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allowed_methods=self.allowed_methods,
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status_forcelist=self.status_forcelist,
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backoff_factor=self.backoff_factor,
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backoff_max=self.backoff_max,
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raise_on_redirect=self.raise_on_redirect,
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raise_on_status=self.raise_on_status,
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history=self.history,
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remove_headers_on_redirect=self.remove_headers_on_redirect,
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respect_retry_after_header=self.respect_retry_after_header,
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backoff_jitter=self.backoff_jitter,
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)
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params.update(kw)
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return type(self)(**params) # type: ignore[arg-type]
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@classmethod
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def from_int(
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cls,
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retries: Retry | bool | int | None,
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redirect: bool | int | None = True,
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default: Retry | bool | int | None = None,
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) -> Retry:
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"""Backwards-compatibility for the old retries format."""
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if retries is None:
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retries = default if default is not None else cls.DEFAULT
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if isinstance(retries, Retry):
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return retries
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redirect = bool(redirect) and None
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new_retries = cls(retries, redirect=redirect)
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log.debug("Converted retries value: %r -> %r", retries, new_retries)
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return new_retries
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def get_backoff_time(self) -> float:
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"""Formula for computing the current backoff
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:rtype: float
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"""
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# We want to consider only the last consecutive errors sequence (Ignore redirects).
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consecutive_errors_len = len(
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list(
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takewhile(lambda x: x.redirect_location is None, reversed(self.history))
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)
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)
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if consecutive_errors_len <= 1:
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return 0
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backoff_value = self.backoff_factor * (2 ** (consecutive_errors_len - 1))
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if self.backoff_jitter != 0.0:
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backoff_value += random.random() * self.backoff_jitter
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return float(max(0, min(self.backoff_max, backoff_value)))
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def parse_retry_after(self, retry_after: str) -> float:
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seconds: float
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# Whitespace: https://tools.ietf.org/html/rfc7230#section-3.2.4
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if re.match(r"^\s*[0-9]+\s*$", retry_after):
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seconds = int(retry_after)
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else:
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retry_date_tuple = email.utils.parsedate_tz(retry_after)
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if retry_date_tuple is None:
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raise InvalidHeader(f"Invalid Retry-After header: {retry_after}")
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retry_date = email.utils.mktime_tz(retry_date_tuple)
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seconds = retry_date - time.time()
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seconds = max(seconds, 0)
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return seconds
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def get_retry_after(self, response: BaseHTTPResponse) -> float | None:
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"""Get the value of Retry-After in seconds."""
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retry_after = response.headers.get("Retry-After")
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if retry_after is None:
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return None
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return self.parse_retry_after(retry_after)
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def sleep_for_retry(self, response: BaseHTTPResponse) -> bool:
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retry_after = self.get_retry_after(response)
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if retry_after:
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time.sleep(retry_after)
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return True
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return False
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def _sleep_backoff(self) -> None:
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backoff = self.get_backoff_time()
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if backoff <= 0:
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return
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time.sleep(backoff)
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def sleep(self, response: BaseHTTPResponse | None = None) -> None:
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"""Sleep between retry attempts.
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This method will respect a server's ``Retry-After`` response header
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and sleep the duration of the time requested. If that is not present, it
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will use an exponential backoff. By default, the backoff factor is 0 and
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this method will return immediately.
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"""
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if self.respect_retry_after_header and response:
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slept = self.sleep_for_retry(response)
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if slept:
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return
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self._sleep_backoff()
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def _is_connection_error(self, err: Exception) -> bool:
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"""Errors when we're fairly sure that the server did not receive the
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request, so it should be safe to retry.
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"""
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if isinstance(err, ProxyError):
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err = err.original_error
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return isinstance(err, ConnectTimeoutError)
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def _is_read_error(self, err: Exception) -> bool:
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"""Errors that occur after the request has been started, so we should
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assume that the server began processing it.
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"""
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return isinstance(err, (ReadTimeoutError, ProtocolError))
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def _is_method_retryable(self, method: str) -> bool:
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"""Checks if a given HTTP method should be retried upon, depending if
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it is included in the allowed_methods
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"""
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if self.allowed_methods and method.upper() not in self.allowed_methods:
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return False
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return True
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def is_retry(
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self, method: str, status_code: int, has_retry_after: bool = False
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) -> bool:
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"""Is this method/status code retryable? (Based on allowlists and control
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variables such as the number of total retries to allow, whether to
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respect the Retry-After header, whether this header is present, and
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whether the returned status code is on the list of status codes to
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be retried upon on the presence of the aforementioned header)
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"""
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if not self._is_method_retryable(method):
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return False
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if self.status_forcelist and status_code in self.status_forcelist:
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return True
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return bool(
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self.total
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and self.respect_retry_after_header
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and has_retry_after
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and (status_code in self.RETRY_AFTER_STATUS_CODES)
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)
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def is_exhausted(self) -> bool:
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"""Are we out of retries?"""
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retry_counts = [
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x
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for x in (
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self.total,
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self.connect,
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self.read,
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self.redirect,
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self.status,
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self.other,
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)
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if x
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]
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if not retry_counts:
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return False
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return min(retry_counts) < 0
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def increment(
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self,
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method: str | None = None,
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url: str | None = None,
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response: BaseHTTPResponse | None = None,
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error: Exception | None = None,
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_pool: ConnectionPool | None = None,
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_stacktrace: TracebackType | None = None,
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) -> Retry:
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"""Return a new Retry object with incremented retry counters.
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:param response: A response object, or None, if the server did not
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return a response.
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:type response: :class:`~urllib3.response.BaseHTTPResponse`
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:param Exception error: An error encountered during the request, or
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None if the response was received successfully.
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:return: A new ``Retry`` object.
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"""
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if self.total is False and error:
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# Disabled, indicate to re-raise the error.
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raise reraise(type(error), error, _stacktrace)
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total = self.total
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if total is not None:
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total -= 1
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connect = self.connect
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read = self.read
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redirect = self.redirect
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status_count = self.status
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other = self.other
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cause = "unknown"
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status = None
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redirect_location = None
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if error and self._is_connection_error(error):
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# Connect retry?
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if connect is False:
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raise reraise(type(error), error, _stacktrace)
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elif connect is not None:
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connect -= 1
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elif error and self._is_read_error(error):
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# Read retry?
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if read is False or method is None or not self._is_method_retryable(method):
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raise reraise(type(error), error, _stacktrace)
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elif read is not None:
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read -= 1
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elif error:
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# Other retry?
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if other is not None:
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other -= 1
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elif response and response.get_redirect_location():
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# Redirect retry?
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if redirect is not None:
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redirect -= 1
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cause = "too many redirects"
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response_redirect_location = response.get_redirect_location()
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if response_redirect_location:
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redirect_location = response_redirect_location
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status = response.status
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else:
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# Incrementing because of a server error like a 500 in
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# status_forcelist and the given method is in the allowed_methods
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cause = ResponseError.GENERIC_ERROR
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if response and response.status:
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if status_count is not None:
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status_count -= 1
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cause = ResponseError.SPECIFIC_ERROR.format(status_code=response.status)
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status = response.status
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history = self.history + (
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RequestHistory(method, url, error, status, redirect_location),
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)
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new_retry = self.new(
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total=total,
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connect=connect,
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read=read,
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redirect=redirect,
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status=status_count,
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other=other,
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history=history,
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)
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if new_retry.is_exhausted():
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reason = error or ResponseError(cause)
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raise MaxRetryError(_pool, url, reason) from reason # type: ignore[arg-type]
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log.debug("Incremented Retry for (url='%s'): %r", url, new_retry)
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return new_retry
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def __repr__(self) -> str:
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return (
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f"{type(self).__name__}(total={self.total}, connect={self.connect}, "
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f"read={self.read}, redirect={self.redirect}, status={self.status})"
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)
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# For backwards compatibility (equivalent to pre-v1.9):
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Retry.DEFAULT = Retry(3)
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