This package provides support for enhanced context based waiting. This module will greatly enhance the information presented when a wait timeout occurs. Wait contexts are particularly useful for distributed automation. Distributed automation scenarios required lots of wait loops in order wait for the effects of an effect to distributed throughout the distributed system.
The waiting code patterns used are designed to present the best results in test stacktraces presented when a wait fails. This makes the mojo.waiting module perfect for use with test frameworks such as pytest and testplus that show code context in the error report stack traces.
Another important aspect of the mojo.waiting module is that it uses datetime timestamps and timespan for lengths of time so timeouts in error reporting are easier to interpret.
Traceback (most recent call last):
File "/home/myron/repos/mojo.waiting/source/tests/test_wait_for_it.py", line 97, in test_basic_wait_for_it_timeout
future.result()
File "/usr/lib/python3.10/concurrent/futures/_base.py", line 451, in result
return self.__get_result()
File "/usr/lib/python3.10/concurrent/futures/_base.py", line 403, in __get_result
raise self._exception
File "/usr/lib/python3.10/concurrent/futures/thread.py", line 58, in run
result = self.fn(*self.args, **self.kwargs)
File "/home/myron/repos/mojo.waiting/source/tests/test_wait_for_it.py", line 88, in wait_task
ctxwait.wait_for_it(wait_helper, interval=.5, timeout=2)
File "/home/myron/repos/mojo.waiting/source/packages/ctxwait/waiting.py", line 103, in wait_for_it
raise toerr
TimeoutError: Timeout waiting for 'wait_helper':
timeout=2 start_time=2023-03-13 14:57:29.860302, end_time=2023-03-13 14:57:31.860302 now_time=2023-03-13 14:57:31.863681 time_diff=0:00:02.003379
The following is an example of how the mojo.waiting module is used.
from ctxwait import WaitContext, wait_for_it
def some_wait_helper(wctx: WaitContext):
finished = False
// TODO: Check if something is finished, the code and variables used
// here will show up in any tracebacks from pytest or testplus
// because the timeout is being raised in the appropriate scope.
if not finished and wctx.final_attempt:
whatfor = "Test timeout"
toerr = wctx.create_timeout(whatfor)
raise toerr
return finished
wait_for_it(some_wait_helper)The wait_for_it method has many different parameters that can be used to override the behavior of the wait loop.
def wait_for_it(looper: WaitCallback, *largs, what_for: Optional[str]=None, delay: float=DEFAULT_WAIT_DELAY,
interval: float=DEFAULT_WAIT_INTERVAL, timeout: float=DEFAULT_WAIT_TIMEOUT,
lkwargs: Dict[Any, Any]={}, wctx: Optional[WaitContext]=None):
"""
Provides for convenient mechanism to wait for criteria to be met before proceeding.
:param looper: A callback method that is repeatedly called while it returns `False` up-to
the end of a timeout period, and that will return `True` if a waited on
condition is met prior to a timeout condition being met.
:param largs: Arguements to pass to the looper callback function.
:param what_for: A breif description of what is being waited for.
:param delay: An initial time delay to consume before beginning the waiting process.
:param interval: A period of time to delay between rechecks of the wait conditon
:param timeout: The maximum period of time in seconds that should be waited before timing out.
:param lkwargs: Additional keyword arguments to pass to the looper function
:raises TimeoutError: A timeout error with details around the wait condition.
..note: The 'delay', 'interval' and 'timeout' parameters will be ignored if the 'wctx' parameter
is passed as the wctx (WaitContext) parameter includes these values with it.
"""
...The wait_for_it function must be passed a method that follows the WaitCallback protocol. The function can have variable arguments and keyword arguements but the first parameter to the WaitCallback method must be a WaitContext object.