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timeout.py
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# The default socket timeout, used by httplib to indicate that no timeout was
# specified by the user
from socket import _GLOBAL_DEFAULT_TIMEOUT
import time
from ..exceptions import TimeoutStateError
# A sentinel value to indicate that no timeout was specified by the user in
# urllib3
_Default = object()
def current_time():
"""
Retrieve the current time. This function is mocked out in unit testing.
"""
return time.time()
class Timeout(object):
""" Timeout configuration.
Timeouts can be defined as a default for a pool::
timeout = Timeout(connect=2.0, read=7.0)
http = PoolManager(timeout=timeout)
response = http.request('GET', 'http://example.com/')
Or per-request (which overrides the default for the pool)::
response = http.request('GET', 'http://example.com/', timeout=Timeout(10))
Timeouts can be disabled by setting all the parameters to ``None``::
no_timeout = Timeout(connect=None, read=None)
response = http.request('GET', 'http://example.com/, timeout=no_timeout)
:param total:
This combines the connect and read timeouts into one; the read timeout
will be set to the time leftover from the connect attempt. In the
event that both a connect timeout and a total are specified, or a read
timeout and a total are specified, the shorter timeout will be applied.
Defaults to None.
:type total: integer, float, or None
:param connect:
The maximum amount of time to wait for a connection attempt to a server
to succeed. Omitting the parameter will default the connect timeout to
the system default, probably `the global default timeout in socket.py
<http://hg.python.org/cpython/file/603b4d593758/Lib/socket.py#l535>`_.
None will set an infinite timeout for connection attempts.
:type connect: integer, float, or None
:param read:
The maximum amount of time to wait between consecutive
read operations for a response from the server. Omitting
the parameter will default the read timeout to the system
default, probably `the global default timeout in socket.py
<http://hg.python.org/cpython/file/603b4d593758/Lib/socket.py#l535>`_.
None will set an infinite timeout.
:type read: integer, float, or None
.. note::
Many factors can affect the total amount of time for urllib3 to return
an HTTP response.
For example, Python's DNS resolver does not obey the timeout specified
on the socket. Other factors that can affect total request time include
high CPU load, high swap, the program running at a low priority level,
or other behaviors.
In addition, the read and total timeouts only measure the time between
read operations on the socket connecting the client and the server,
not the total amount of time for the request to return a complete
response. For most requests, the timeout is raised because the server
has not sent the first byte in the specified time. This is not always
the case; if a server streams one byte every fifteen seconds, a timeout
of 20 seconds will not trigger, even though the request will take
several minutes to complete.
If your goal is to cut off any request after a set amount of wall clock
time, consider having a second "watcher" thread to cut off a slow
request.
"""
#: A sentinel object representing the default timeout value
DEFAULT_TIMEOUT = _GLOBAL_DEFAULT_TIMEOUT
def __init__(self, total=None, connect=_Default, read=_Default):
self._connect = self._validate_timeout(connect, 'connect')
self._read = self._validate_timeout(read, 'read')
self.total = self._validate_timeout(total, 'total')
self._start_connect = None
def __str__(self):
return '%s(connect=%r, read=%r, total=%r)' % (
type(self).__name__, self._connect, self._read, self.total)
@classmethod
def _validate_timeout(cls, value, name):
""" Check that a timeout attribute is valid.
:param value: The timeout value to validate
:param name: The name of the timeout attribute to validate. This is
used to specify in error messages.
:return: The validated and casted version of the given value.
:raises ValueError: If the type is not an integer or a float, or if it
is a numeric value less than zero.
"""
if value is _Default:
return cls.DEFAULT_TIMEOUT
if value is None or value is cls.DEFAULT_TIMEOUT:
return value
try:
float(value)
except (TypeError, ValueError):
raise ValueError("Timeout value %s was %s, but it must be an "
"int or float." % (name, value))
try:
if value < 0:
raise ValueError("Attempted to set %s timeout to %s, but the "
"timeout cannot be set to a value less "
"than 0." % (name, value))
except TypeError: # Python 3
raise ValueError("Timeout value %s was %s, but it must be an "
"int or float." % (name, value))
return value
@classmethod
def from_float(cls, timeout):
""" Create a new Timeout from a legacy timeout value.
The timeout value used by httplib.py sets the same timeout on the
connect(), and recv() socket requests. This creates a :class:`Timeout`
object that sets the individual timeouts to the ``timeout`` value
passed to this function.
:param timeout: The legacy timeout value.
:type timeout: integer, float, sentinel default object, or None
:return: Timeout object
:rtype: :class:`Timeout`
"""
return Timeout(read=timeout, connect=timeout)
def clone(self):
""" Create a copy of the timeout object
Timeout properties are stored per-pool but each request needs a fresh
Timeout object to ensure each one has its own start/stop configured.
:return: a copy of the timeout object
:rtype: :class:`Timeout`
"""
# We can't use copy.deepcopy because that will also create a new object
# for _GLOBAL_DEFAULT_TIMEOUT, which socket.py uses as a sentinel to
# detect the user default.
return Timeout(connect=self._connect, read=self._read,
total=self.total)
def start_connect(self):
""" Start the timeout clock, used during a connect() attempt
:raises urllib3.exceptions.TimeoutStateError: if you attempt
to start a timer that has been started already.
"""
if self._start_connect is not None:
raise TimeoutStateError("Timeout timer has already been started.")
self._start_connect = current_time()
return self._start_connect
def get_connect_duration(self):
""" Gets the time elapsed since the call to :meth:`start_connect`.
:return: Elapsed time.
:rtype: float
:raises urllib3.exceptions.TimeoutStateError: if you attempt
to get duration for a timer that hasn't been started.
"""
if self._start_connect is None:
raise TimeoutStateError("Can't get connect duration for timer "
"that has not started.")
return current_time() - self._start_connect
@property
def connect_timeout(self):
""" Get the value to use when setting a connection timeout.
This will be a positive float or integer, the value None
(never timeout), or the default system timeout.
:return: Connect timeout.
:rtype: int, float, :attr:`Timeout.DEFAULT_TIMEOUT` or None
"""
if self.total is None:
return self._connect
if self._connect is None or self._connect is self.DEFAULT_TIMEOUT:
return self.total
return min(self._connect, self.total)
@property
def read_timeout(self):
""" Get the value for the read timeout.
This assumes some time has elapsed in the connection timeout and
computes the read timeout appropriately.
If self.total is set, the read timeout is dependent on the amount of
time taken by the connect timeout. If the connection time has not been
established, a :exc:`~urllib3.exceptions.TimeoutStateError` will be
raised.
:return: Value to use for the read timeout.
:rtype: int, float, :attr:`Timeout.DEFAULT_TIMEOUT` or None
:raises urllib3.exceptions.TimeoutStateError: If :meth:`start_connect`
has not yet been called on this object.
"""
if (self.total is not None and
self.total is not self.DEFAULT_TIMEOUT and
self._read is not None and
self._read is not self.DEFAULT_TIMEOUT):
# In case the connect timeout has not yet been established.
if self._start_connect is None:
return self._read
return max(0, min(self.total - self.get_connect_duration(),
self._read))
elif self.total is not None and self.total is not self.DEFAULT_TIMEOUT:
return max(0, self.total - self.get_connect_duration())
else:
return self._read

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