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- Clear release notes - Add test for `reset()` while a timer is being waited on - Fix reseting the timer while it is being waited on - Update the release notes - Fix typo in comment Fixes #242.
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# Frequenz Channels Release Notes | ||
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## Summary | ||
## Bug Fixes | ||
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The minimum Python supported version was bumped to 3.11 and the `Select` class replaced by the new `select()` function. | ||
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## Upgrading | ||
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* The minimum supported Python version was bumped to 3.11, downstream projects will need to upgrade too to use this version. | ||
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* The `Select` class was replaced by a new `select()` function, with the following improvements: | ||
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* Type-safe: proper type hinting by using the new helper type guard `selected_from()`. | ||
* Fixes potential starvation issues. | ||
* Simplifies the interface by providing values one-by-one. | ||
* Guarantees there are no dangling tasks left behind when used as an async context manager. | ||
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This new function is an [async iterator](https://docs.python.org/3.11/library/collections.abc.html#collections.abc.AsyncIterator), and makes sure no dangling tasks are left behind after a select loop is done. | ||
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Example: | ||
```python | ||
timer1 = Timer.periodic(datetime.timedelta(seconds=1)) | ||
timer2 = Timer.timeout(datetime.timedelta(seconds=0.5)) | ||
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async for selected in select(timer1, timer2): | ||
if selected_from(selected, timer1): | ||
# Beware: `selected.value` might raise an exception, you can always | ||
# check for exceptions with `selected.exception` first or use | ||
# a try-except block. You can also quickly check if the receiver was | ||
# stopped and let any other unexpected exceptions bubble up. | ||
if selected.was_stopped(): | ||
print("timer1 was stopped") | ||
continue | ||
print(f"timer1: now={datetime.datetime.now()} drift={selected.value}") | ||
timer2.stop() | ||
elif selected_from(selected, timer2): | ||
# Explicitly handling of exceptions | ||
match selected.exception: | ||
case ReceiverStoppedError(): | ||
print("timer2 was stopped") | ||
case Exception() as exception: | ||
print(f"timer2: exception={exception}") | ||
case None: | ||
# All good, no exception, we can use `selected.value` safely | ||
print( | ||
f"timer2: now={datetime.datetime.now()} " | ||
f"drift={selected.value}" | ||
) | ||
case _ as unhanded: | ||
assert_never(unhanded) | ||
else: | ||
# This is not necessary, as select() will check for exhaustiveness, but | ||
# it is good practice to have it in case you forgot to handle a new | ||
# receiver added to `select()` at a later point in time. | ||
assert False | ||
``` | ||
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## New Features | ||
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* A new `select()` function was added, please look at the *Upgrading* section for details. | ||
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* A new `Event` utility receiver was added. | ||
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This receiver can be made ready manually. It is mainly useful for testing but can also become handy in scenarios where a simple, on-off signal needs to be sent to a select loop for example. | ||
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Example: | ||
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```python | ||
import asyncio | ||
from frequenz.channels import Receiver | ||
from frequenz.channels.util import Event, select, selected_from | ||
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other_receiver: Receiver[int] = ... | ||
exit_event = Event() | ||
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async def exit_after_10_seconds() -> None: | ||
asyncio.sleep(10) | ||
exit_event.set() | ||
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asyncio.ensure_future(exit_after_10_seconds()) | ||
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async for selected in select(exit_event, other_receiver): | ||
if selected_from(selected, exit_event): | ||
break | ||
if selected_from(selected, other_receiver): | ||
print(selected.value) | ||
else: | ||
assert False, "Unknow receiver selected" | ||
``` | ||
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* The `Timer` class now has more descriptive `__str__` and `__repr__` methods. | ||
* `Timer`: Fix bug that was causing calls to `reset()` to not reset the timer, if the timer was already being awaited. |
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# License: MIT | ||
# Copyright © 2023 Frequenz Energy-as-a-Service GmbH | ||
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"""Integration tests for the timer.""" | ||
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import asyncio | ||
from datetime import timedelta | ||
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import async_solipsism | ||
import pytest | ||
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from frequenz.channels.util import Timer | ||
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@pytest.mark.integration | ||
async def test_timer_timeout_reset( | ||
event_loop: async_solipsism.EventLoop, # pylint: disable=redefined-outer-name | ||
) -> None: | ||
"""Test that the receiving is properly adjusted after a reset.""" | ||
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async def timer_wait(timer: Timer) -> None: | ||
await timer.receive() | ||
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async with asyncio.timeout(2.0): | ||
async with asyncio.TaskGroup() as task_group: | ||
timer = Timer.timeout(timedelta(seconds=1.0)) | ||
start_time = event_loop.time() | ||
task_group.create_task(timer_wait(timer)) | ||
await asyncio.sleep(0.5) | ||
timer.reset() | ||
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run_time = event_loop.time() - start_time | ||
assert run_time >= 1.5 |