Add urllib3 1.22

lib/urllib3/util/retry.py

@@ -0,0 +1,401 @@
+from __future__ import absolute_import
+import time
+import logging
+from collections import namedtuple
+from itertools import takewhile
+import email
+import re
+
+from ..exceptions import (
+    ConnectTimeoutError,
+    MaxRetryError,
+    ProtocolError,
+    ReadTimeoutError,
+    ResponseError,
+    InvalidHeader,
+)
+from ..packages import six
+
+
+log = logging.getLogger(__name__)
+
+# Data structure for representing the metadata of requests that result in a retry.
+RequestHistory = namedtuple('RequestHistory', ["method", "url", "error",
+                                               "status", "redirect_location"])
+
+
+class Retry(object):
+    """ Retry configuration.
+
+    Each retry attempt will create a new Retry object with updated values, so
+    they can be safely reused.
+
+    Retries can be defined as a default for a pool::
+
+        retries = Retry(connect=5, read=2, redirect=5)
+        http = PoolManager(retries=retries)
+        response = http.request('GET', 'http://example.com/')
+
+    Or per-request (which overrides the default for the pool)::
+
+        response = http.request('GET', 'http://example.com/', retries=Retry(10))
+
+    Retries can be disabled by passing ``False``::
+
+        response = http.request('GET', 'http://example.com/', retries=False)
+
+    Errors will be wrapped in :class:`~urllib3.exceptions.MaxRetryError` unless
+    retries are disabled, in which case the causing exception will be raised.
+
+    :param int total:
+        Total number of retries to allow. Takes precedence over other counts.
+
+        Set to ``None`` to remove this constraint and fall back on other
+        counts. It's a good idea to set this to some sensibly-high value to
+        account for unexpected edge cases and avoid infinite retry loops.
+
+        Set to ``0`` to fail on the first retry.
+
+        Set to ``False`` to disable and imply ``raise_on_redirect=False``.
+
+    :param int connect:
+        How many connection-related errors to retry on.
+
+        These are errors raised before the request is sent to the remote server,
+        which we assume has not triggered the server to process the request.
+
+        Set to ``0`` to fail on the first retry of this type.
+
+    :param int read:
+        How many times to retry on read errors.
+
+        These errors are raised after the request was sent to the server, so the
+        request may have side-effects.
+
+        Set to ``0`` to fail on the first retry of this type.
+
+    :param int redirect:
+        How many redirects to perform. Limit this to avoid infinite redirect
+        loops.
+
+        A redirect is a HTTP response with a status code 301, 302, 303, 307 or
+        308.
+
+        Set to ``0`` to fail on the first retry of this type.
+
+        Set to ``False`` to disable and imply ``raise_on_redirect=False``.
+
+    :param int status:
+        How many times to retry on bad status codes.
+
+        These are retries made on responses, where status code matches
+        ``status_forcelist``.
+
+        Set to ``0`` to fail on the first retry of this type.
+
+    :param iterable method_whitelist:
+        Set of uppercased HTTP method verbs that we should retry on.
+
+        By default, we only retry on methods which are considered to be
+        idempotent (multiple requests with the same parameters end with the
+        same state). See :attr:`Retry.DEFAULT_METHOD_WHITELIST`.
+
+        Set to a ``False`` value to retry on any verb.
+
+    :param iterable status_forcelist:
+        A set of integer HTTP status codes that we should force a retry on.
+        A retry is initiated if the request method is in ``method_whitelist``
+        and the response status code is in ``status_forcelist``.
+
+        By default, this is disabled with ``None``.
+
+    :param float backoff_factor:
+        A backoff factor to apply between attempts after the second try
+        (most errors are resolved immediately by a second try without a
+        delay). urllib3 will sleep for::
+
+            {backoff factor} * (2 ^ ({number of total retries} - 1))
+
+        seconds. If the backoff_factor is 0.1, then :func:`.sleep` will sleep
+        for [0.0s, 0.2s, 0.4s, ...] between retries. It will never be longer
+        than :attr:`Retry.BACKOFF_MAX`.
+
+        By default, backoff is disabled (set to 0).
+
+    :param bool raise_on_redirect: Whether, if the number of redirects is
+        exhausted, to raise a MaxRetryError, or to return a response with a
+        response code in the 3xx range.
+
+    :param bool raise_on_status: Similar meaning to ``raise_on_redirect``:
+        whether we should raise an exception, or return a response,
+        if status falls in ``status_forcelist`` range and retries have
+        been exhausted.
+
+    :param tuple history: The history of the request encountered during
+        each call to :meth:`~Retry.increment`. The list is in the order
+        the requests occurred. Each list item is of class :class:`RequestHistory`.
+
+    :param bool respect_retry_after_header:
+        Whether to respect Retry-After header on status codes defined as
+        :attr:`Retry.RETRY_AFTER_STATUS_CODES` or not.
+
+    """
+
+    DEFAULT_METHOD_WHITELIST = frozenset([
+        'HEAD', 'GET', 'PUT', 'DELETE', 'OPTIONS', 'TRACE'])
+
+    RETRY_AFTER_STATUS_CODES = frozenset([413, 429, 503])
+
+    #: Maximum backoff time.
+    BACKOFF_MAX = 120
+
+    def __init__(self, total=10, connect=None, read=None, redirect=None, status=None,
+                 method_whitelist=DEFAULT_METHOD_WHITELIST, status_forcelist=None,
+                 backoff_factor=0, raise_on_redirect=True, raise_on_status=True,
+                 history=None, respect_retry_after_header=True):
+
+        self.total = total
+        self.connect = connect
+        self.read = read
+        self.status = status
+
+        if redirect is False or total is False:
+            redirect = 0
+            raise_on_redirect = False
+
+        self.redirect = redirect
+        self.status_forcelist = status_forcelist or set()
+        self.method_whitelist = method_whitelist
+        self.backoff_factor = backoff_factor
+        self.raise_on_redirect = raise_on_redirect
+        self.raise_on_status = raise_on_status
+        self.history = history or tuple()
+        self.respect_retry_after_header = respect_retry_after_header
+
+    def new(self, **kw):
+        params = dict(
+            total=self.total,
+            connect=self.connect, read=self.read, redirect=self.redirect, status=self.status,
+            method_whitelist=self.method_whitelist,
+            status_forcelist=self.status_forcelist,
+            backoff_factor=self.backoff_factor,
+            raise_on_redirect=self.raise_on_redirect,
+            raise_on_status=self.raise_on_status,
+            history=self.history,
+        )
+        params.update(kw)
+        return type(self)(**params)
+
+    @classmethod
+    def from_int(cls, retries, redirect=True, default=None):
+        """ Backwards-compatibility for the old retries format."""
+        if retries is None:
+            retries = default if default is not None else cls.DEFAULT
+
+        if isinstance(retries, Retry):
+            return retries
+
+        redirect = bool(redirect) and None
+        new_retries = cls(retries, redirect=redirect)
+        log.debug("Converted retries value: %r -> %r", retries, new_retries)
+        return new_retries
+
+    def get_backoff_time(self):
+        """ Formula for computing the current backoff
+
+        :rtype: float
+        """
+        # We want to consider only the last consecutive errors sequence (Ignore redirects).
+        consecutive_errors_len = len(list(takewhile(lambda x: x.redirect_location is None,
+                                                    reversed(self.history))))
+        if consecutive_errors_len <= 1:
+            return 0
+
+        backoff_value = self.backoff_factor * (2 ** (consecutive_errors_len - 1))
+        return min(self.BACKOFF_MAX, backoff_value)
+
+    def parse_retry_after(self, retry_after):
+        # Whitespace: https://tools.ietf.org/html/rfc7230#section-3.2.4
+        if re.match(r"^\s*[0-9]+\s*$", retry_after):
+            seconds = int(retry_after)
+        else:
+            retry_date_tuple = email.utils.parsedate(retry_after)
+            if retry_date_tuple is None:
+                raise InvalidHeader("Invalid Retry-After header: %s" % retry_after)
+            retry_date = time.mktime(retry_date_tuple)
+            seconds = retry_date - time.time()
+
+        if seconds < 0:
+            seconds = 0
+
+        return seconds
+
+    def get_retry_after(self, response):
+        """ Get the value of Retry-After in seconds. """
+
+        retry_after = response.getheader("Retry-After")
+
+        if retry_after is None:
+            return None
+
+        return self.parse_retry_after(retry_after)
+
+    def sleep_for_retry(self, response=None):
+        retry_after = self.get_retry_after(response)
+        if retry_after:
+            time.sleep(retry_after)
+            return True
+
+        return False
+
+    def _sleep_backoff(self):
+        backoff = self.get_backoff_time()
+        if backoff <= 0:
+            return
+        time.sleep(backoff)
+
+    def sleep(self, response=None):
+        """ Sleep between retry attempts.
+
+        This method will respect a server's ``Retry-After`` response header
+        and sleep the duration of the time requested. If that is not present, it
+        will use an exponential backoff. By default, the backoff factor is 0 and
+        this method will return immediately.
+        """
+
+        if response:
+            slept = self.sleep_for_retry(response)
+            if slept:
+                return
+
+        self._sleep_backoff()
+
+    def _is_connection_error(self, err):
+        """ Errors when we're fairly sure that the server did not receive the
+        request, so it should be safe to retry.
+        """
+        return isinstance(err, ConnectTimeoutError)
+
+    def _is_read_error(self, err):
+        """ Errors that occur after the request has been started, so we should
+        assume that the server began processing it.
+        """
+        return isinstance(err, (ReadTimeoutError, ProtocolError))
+
+    def _is_method_retryable(self, method):
+        """ Checks if a given HTTP method should be retried upon, depending if
+        it is included on the method whitelist.
+        """
+        if self.method_whitelist and method.upper() not in self.method_whitelist:
+            return False
+
+        return True
+
+    def is_retry(self, method, status_code, has_retry_after=False):
+        """ Is this method/status code retryable? (Based on whitelists and control
+        variables such as the number of total retries to allow, whether to
+        respect the Retry-After header, whether this header is present, and
+        whether the returned status code is on the list of status codes to
+        be retried upon on the presence of the aforementioned header)
+        """
+        if not self._is_method_retryable(method):
+            return False
+
+        if self.status_forcelist and status_code in self.status_forcelist:
+            return True
+
+        return (self.total and self.respect_retry_after_header and
+                has_retry_after and (status_code in self.RETRY_AFTER_STATUS_CODES))
+
+    def is_exhausted(self):
+        """ Are we out of retries? """
+        retry_counts = (self.total, self.connect, self.read, self.redirect, self.status)
+        retry_counts = list(filter(None, retry_counts))
+        if not retry_counts:
+            return False
+
+        return min(retry_counts) < 0
+
+    def increment(self, method=None, url=None, response=None, error=None,
+                  _pool=None, _stacktrace=None):
+        """ Return a new Retry object with incremented retry counters.
+
+        :param response: A response object, or None, if the server did not
+            return a response.
+        :type response: :class:`~urllib3.response.HTTPResponse`
+        :param Exception error: An error encountered during the request, or
+            None if the response was received successfully.
+
+        :return: A new ``Retry`` object.
+        """
+        if self.total is False and error:
+            # Disabled, indicate to re-raise the error.
+            raise six.reraise(type(error), error, _stacktrace)
+
+        total = self.total
+        if total is not None:
+            total -= 1
+
+        connect = self.connect
+        read = self.read
+        redirect = self.redirect
+        status_count = self.status
+        cause = 'unknown'
+        status = None
+        redirect_location = None
+
+        if error and self._is_connection_error(error):
+            # Connect retry?
+            if connect is False:
+                raise six.reraise(type(error), error, _stacktrace)
+            elif connect is not None:
+                connect -= 1
+
+        elif error and self._is_read_error(error):
+            # Read retry?
+            if read is False or not self._is_method_retryable(method):
+                raise six.reraise(type(error), error, _stacktrace)
+            elif read is not None:
+                read -= 1
+
+        elif response and response.get_redirect_location():
+            # Redirect retry?
+            if redirect is not None:
+                redirect -= 1
+            cause = 'too many redirects'
+            redirect_location = response.get_redirect_location()
+            status = response.status
+
+        else:
+            # Incrementing because of a server error like a 500 in
+            # status_forcelist and a the given method is in the whitelist
+            cause = ResponseError.GENERIC_ERROR
+            if response and response.status:
+                if status_count is not None:
+                    status_count -= 1
+                cause = ResponseError.SPECIFIC_ERROR.format(
+                    status_code=response.status)
+                status = response.status
+
+        history = self.history + (RequestHistory(method, url, error, status, redirect_location),)
+
+        new_retry = self.new(
+            total=total,
+            connect=connect, read=read, redirect=redirect, status=status_count,
+            history=history)
+
+        if new_retry.is_exhausted():
+            raise MaxRetryError(_pool, url, error or ResponseError(cause))
+
+        log.debug("Incremented Retry for (url='%s'): %r", url, new_retry)
+
+        return new_retry
+
+    def __repr__(self):
+        return ('{cls.__name__}(total={self.total}, connect={self.connect}, '
+                'read={self.read}, redirect={self.redirect}, status={self.status})').format(
+                    cls=type(self), self=self)
+
+
+# For backwards compatibility (equivalent to pre-v1.9):
+Retry.DEFAULT = Retry(3)