[MovingWindow] Add a trigger that fires after having received a fixed number of samples

[matthias-wende-frequenz]

What's needed?

Currently there is no clean way to wait until the MovingWindow got updated with a certain number of samples.
This feature has been requested in the past and there has been an initial implemented attempt #387.

This feature has been requested again now by @cwasicki.

Proposed solution

Introduce an asynchronous wait_for_samples method that returns once the requested number of new samples has been stored in the MovingWindow.

Use cases

• replace a while loop in the Forecast actor (Add method to MovingWindow that waits for a number of samples #387 (comment))

Alternatives and workarounds

No response

Additional context

No response

[cwasicki]

It would be great if this could be part of v1.0 since we are still working around this with sleep calls. What was the issue with the implementation in the PR that was mentioned above?

FYI @phillip-wenig-frequenz

[llucax]

It think it should not be hard to implement using a condition. Just add a wait method that calls cond.wait() and then each time a sample is received increment an internal counter and call cond.notify_all() once the desired number was reached. Probably even an event could be enough.

There was an attempt using a channel to communicate when the samples were received, but I'm not sure that complexity is needed, if we need a receiver, we can use (an expose) an Event receiver instead.

[matthias-wende-frequenz]

Actually Channels could be seen as a convenience wrapper on top of condition objects.

[matthias-wende-frequenz]

It would be great if this could be part of v1.0 since we are still working around this with sleep calls. What was the issue with the implementation in the PR that was mentioned above?

AFAIR there is no issue. Someone has to pick it up.