"""Abstraction for waiting on API conditions to become true."""
import time
from typing import (
Callable,
Optional,
Union,
)
DEFAULT_POLLING_BACKOFF = 0
DEFAULT_POLLING_DELTA = 0.25
TIMEOUT_MESSAGE_TEMPLATE = "Timed out after {} seconds waiting on {}."
timeout_type = Union[int, float]
[docs]
def wait_on(
function: Callable,
desc: str,
timeout: timeout_type,
delta: timeout_type = DEFAULT_POLLING_DELTA,
polling_backoff: timeout_type = DEFAULT_POLLING_BACKOFF,
sleep_: Optional[Callable] = None,
):
"""Wait for function to return non-None value.
Grow the polling interval (initially ``delta`` defaulting to 0.25 seconds)
incrementally by the supplied ``polling_backoff`` (defaulting to 0).
Throw a TimeoutAssertionError if the supplied timeout is reached without
supplied function ever returning a non-None value.
"""
sleep = sleep_ or time.sleep
total_wait = 0.0
while True:
if total_wait > timeout:
raise TimeoutAssertionError(TIMEOUT_MESSAGE_TEMPLATE.format(total_wait, desc))
value = function()
if value is not None:
return value
total_wait += delta
sleep(delta)
delta += polling_backoff
[docs]
class TimeoutAssertionError(AssertionError):
"""Derivative of AssertionError indicating wait_on exceeded max time."""
[docs]
def __init__(self, message):
super().__init__(message)