Source code for webtraversallibrary.processtools
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# to you under the Apache License, Version 2.0 (the
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"""
Module collecting helper functions for common processing tasks, such as muting stdout within a context.
"""
import logging
import os
import signal
from threading import Thread
from time import sleep
from webtraversallibrary.driver_check import OS, get_current_os
logger = logging.getLogger("wtl")
_ON_WINDOWS = get_current_os() == OS.WINDOWS
[docs]class cached_property:
"""
Decorator that caches a property return value and will return it on later calls.
Adapted from The Python Cookbok, 2nd edition.
.. note::
If you want to map different arguments to values, use `functools.lru_cache`!
"""
def __init__(self, method):
self.method = method
self.name = method.__name__
self.__doc__ = method.__doc__
def __get__(self, inst, cls):
if inst is None:
return self
result = self.method(inst)
object.__setattr__(inst, self.name, result)
return result
[docs]class Alarm(Thread):
"""Helper class to run a timeout thread on Windows"""
def __init__(self, timeout):
Thread.__init__(self)
self.timeout = timeout
self._stop_gracefully = False
self.daemon = True
def stop(self):
self._stop_gracefully = True
[docs] def run(self):
sleep(self.timeout)
if not self._stop_gracefully:
os._exit(1) # pylint: disable=protected-access
[docs]class TimeoutContext:
"""
Uses :mod:`signal` to raise TimeoutError within the block, if execution went over a specified timeout.
"""
def __init__(self, n_seconds, error_class=TimeoutError):
self.n_seconds = n_seconds
self.error_cls = error_class
self.alarm = None
def __enter__(self):
# pylint: disable=no-member
if self.n_seconds > 0:
if _ON_WINDOWS:
self.alarm = Alarm(self.n_seconds)
self.alarm.start()
else:
signal.signal(signal.SIGALRM, self.raise_error)
signal.alarm(self.n_seconds)
logger.debug(f"TimeoutContext: Operation timeout is set to {self.n_seconds} sec.")
def __exit__(self, *args, **kwargs):
# pylint: disable=no-member
# Cancel the alarm
if self.n_seconds > 0:
if _ON_WINDOWS:
self.alarm.stop()
else:
signal.signal(signal.SIGALRM, signal.SIG_DFL)
time_left = signal.alarm(0)
if time_left <= 0:
logger.debug("TimeoutContext: Operation was interrupted by the timeout")
[docs] def raise_error(self, signal_num, _):
"""
Raises error on timeout.
"""
# pylint: disable=no-member
assert signal_num == signal.SIGALRM
raise self.error_cls(f"Operation timed out after {self.n_seconds} sec.")