def _exponential_timeout_generator(initial, maximum, multiplier, deadline):
"""A generator that yields exponential timeout values.
Args:
initial (float): The initial timeout.
maximum (float): The maximum timeout.
multiplier (float): The multiplier applied to the timeout.
deadline (float): The overall deadline across all invocations.
Yields:
float: A timeout value.
"""
if deadline is not None:
deadline_datetime = (datetime_helpers.utcnow() +
datetime.timedelta(seconds=deadline))
else:
deadline_datetime = datetime.datetime.max
timeout = initial
while True:
now = datetime_helpers.utcnow()
yield min(
# The calculated timeout based on invocations.
timeout,
# The set maximum timeout.
maximum,
# The remaining time before the deadline is reached.
float((deadline_datetime - now).seconds))
timeout = timeout * multiplier
def retry_target(target, predicate, sleep_generator, deadline, on_error=None):
"""Call a function and retry if it fails.
This is the lowest-level retry helper. Generally, you'll use the
higher-level retry helper :class:`Retry`.
Args:
target(Callable): The function to call and retry. This must be a
nullary function - apply arguments with `functools.partial`.
predicate (Callable[Exception]): A callable used to determine if an
exception raised by the target should be considered retryable.
It should return True to retry or False otherwise.
sleep_generator (Iterator[float]): An infinite iterator that determines
how long to sleep between retries.
deadline (float): How long to keep retrying the target.
on_error (Callable): A function to call while processing a retryable
exception. Any error raised by this function will *not* be
caught.
Returns:
Any: the return value of the target function.
Raises:
google.api.core.RetryError: If the deadline is exceeded while retrying.
ValueError: If the sleep generator stops yielding values.
Exception: If the target raises a method that isn't retryable.
"""
if deadline is not None:
deadline_datetime = (datetime_helpers.utcnow() +
datetime.timedelta(seconds=deadline))
else:
deadline_datetime = None
last_exc = None
for sleep in sleep_generator:
try:
return target()
# pylint: disable=broad-except
# This function explicitly must deal with broad exceptions.
except Exception as exc:
if not predicate(exc):
raise
last_exc = exc
if on_error is not None:
on_error(exc)
now = datetime_helpers.utcnow()
if deadline_datetime is not None and deadline_datetime < now:
six.raise_from(
exceptions.RetryError(
'Deadline of {:.1f}s exceeded while calling {}'.format(
deadline, target), last_exc), last_exc)
_LOGGER.debug('Retrying due to {}, sleeping {:.1f}s ...'.format(
last_exc, sleep))
time.sleep(sleep)
raise ValueError('Sleep generator stopped yielding sleep values.')
def test_utcnow():
result = datetime_helpers.utcnow()
assert isinstance(result, datetime.datetime)