411 lines
15 KiB
Python
411 lines
15 KiB
Python
from __future__ import absolute_import
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import time
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import logging
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from collections import namedtuple
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from itertools import takewhile
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import email
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import re
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from ..exceptions import (
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ConnectTimeoutError,
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MaxRetryError,
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ProtocolError,
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ReadTimeoutError,
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ResponseError,
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InvalidHeader,
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)
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from ..packages import six
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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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RequestHistory = namedtuple('RequestHistory', ["method", "url", "error",
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"status", "redirect_location"])
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class Retry(object):
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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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retries = Retry(connect=5, read=2, redirect=5)
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http = PoolManager(retries=retries)
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response = http.request('GET', 'http://example.com/')
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Or per-request (which overrides the default for the pool)::
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response = http.request('GET', 'http://example.com/', retries=Retry(10))
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Retries can be disabled by passing ``False``::
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response = http.request('GET', 'http://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. It's a good idea to set this to some sensibly-high value to
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account for unexpected edge cases and avoid infinite retry loops.
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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 iterable method_whitelist:
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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_METHOD_WHITELIST`.
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Set to a ``False`` value to retry on any verb.
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:param iterable 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 ``method_whitelist``
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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 total retries} - 1))
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seconds. If the backoff_factor is 0.1, then :func:`.sleep` will sleep
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for [0.0s, 0.2s, 0.4s, ...] between retries. It will never be longer
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than :attr:`Retry.BACKOFF_MAX`.
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By default, backoff is disabled (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 iterable 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_METHOD_WHITELIST = frozenset([
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'HEAD', 'GET', 'PUT', 'DELETE', 'OPTIONS', 'TRACE'])
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RETRY_AFTER_STATUS_CODES = frozenset([413, 429, 503])
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DEFAULT_REDIRECT_HEADERS_BLACKLIST = frozenset(['Authorization'])
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#: Maximum backoff time.
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BACKOFF_MAX = 120
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def __init__(self, total=10, connect=None, read=None, redirect=None, status=None,
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method_whitelist=DEFAULT_METHOD_WHITELIST, status_forcelist=None,
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backoff_factor=0, raise_on_redirect=True, raise_on_status=True,
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history=None, respect_retry_after_header=True,
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remove_headers_on_redirect=DEFAULT_REDIRECT_HEADERS_BLACKLIST):
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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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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.method_whitelist = method_whitelist
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self.backoff_factor = backoff_factor
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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 tuple()
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self.respect_retry_after_header = respect_retry_after_header
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self.remove_headers_on_redirect = remove_headers_on_redirect
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def new(self, **kw):
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params = dict(
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total=self.total,
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connect=self.connect, read=self.read, redirect=self.redirect, status=self.status,
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method_whitelist=self.method_whitelist,
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status_forcelist=self.status_forcelist,
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backoff_factor=self.backoff_factor,
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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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)
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params.update(kw)
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return type(self)(**params)
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@classmethod
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def from_int(cls, retries, redirect=True, default=None):
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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):
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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(list(takewhile(lambda x: x.redirect_location is None,
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reversed(self.history))))
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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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return min(self.BACKOFF_MAX, backoff_value)
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def parse_retry_after(self, retry_after):
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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(retry_after)
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if retry_date_tuple is None:
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raise InvalidHeader("Invalid Retry-After header: %s" % retry_after)
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retry_date = time.mktime(retry_date_tuple)
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seconds = retry_date - time.time()
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if seconds < 0:
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seconds = 0
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return seconds
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def get_retry_after(self, response):
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""" Get the value of Retry-After in seconds. """
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retry_after = response.getheader("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=None):
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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):
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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=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 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):
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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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return isinstance(err, ConnectTimeoutError)
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def _is_read_error(self, err):
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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):
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""" Checks if a given HTTP method should be retried upon, depending if
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it is included on the method whitelist.
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"""
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if self.method_whitelist and method.upper() not in self.method_whitelist:
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return False
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return True
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def is_retry(self, method, status_code, has_retry_after=False):
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""" Is this method/status code retryable? (Based on whitelists 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 (self.total and self.respect_retry_after_header and
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has_retry_after and (status_code in self.RETRY_AFTER_STATUS_CODES))
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def is_exhausted(self):
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""" Are we out of retries? """
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retry_counts = (self.total, self.connect, self.read, self.redirect, self.status)
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retry_counts = list(filter(None, retry_counts))
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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(self, method=None, url=None, response=None, error=None,
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_pool=None, _stacktrace=None):
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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.HTTPResponse`
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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 six.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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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 six.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 not self._is_method_retryable(method):
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raise six.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 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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redirect_location = response.get_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 a the given method is in the whitelist
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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(
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status_code=response.status)
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status = response.status
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history = self.history + (RequestHistory(method, url, error, status, redirect_location),)
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new_retry = self.new(
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total=total,
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connect=connect, read=read, redirect=redirect, status=status_count,
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history=history)
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if new_retry.is_exhausted():
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raise MaxRetryError(_pool, url, error or ResponseError(cause))
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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):
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return ('{cls.__name__}(total={self.total}, connect={self.connect}, '
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'read={self.read}, redirect={self.redirect}, status={self.status})').format(
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cls=type(self), self=self)
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# For backwards compatibility (equivalent to pre-v1.9):
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Retry.DEFAULT = Retry(3)
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