[DPL] Feature request - timer callbacks in Data Processor

[knopers8]

A use case:

I have a Quality Control task, that collects all input data into a histogram and publishes the histogram at the end of each cycle. The cycle duration is specified by user. So I need to trigger a process callback whenever new inputs arrive and also perform some additional publishing after a timer expires.
It would useful for me to be able to declare some TimerCallback which is invoked each x seconds.

(noting down our conversation with @ktf, so it is not forgotten)

[ktf]

I think #1319 should allow you to achieve this with an input with "Lifetime::Timer". You can configure the timer by adding (explicitly, for the moment) a ConfigParamSpec with name period-<data-origin>-<data-description> where <data-origin> and <data-description> are the two descriptors you provide in the InputSpec. Period is in milliseconds.

[knopers8]

Thanks, I will try it out on Monday. What do I do, if I want to use '-' in origin or description?
Do you already have in mind a final way of configuring this?

[ktf]

i think it works fine, as what matters is the final option name, not its parts. to be discussed. I would configure them via ConfigParamSpec so that once we integrate it with Configuration they can be controlled from there (as opposed to controlled in the code).

[ktf]

#1354 should cover all the use cases which are not covered already by Lifetime::Timer.

[knopers8]

I am not sure how does that cover my case. It is not possible to access ProcessingContext inside these callbacks, so I see no way of publishing something in there. I could hack it by 'stealing' the DataAllocator reference in the main callback, but still I wouldn't be able to flush it afterwards.

[ktf]

Ah, you are sending the histogram with the usual make() function? Then yes, I need to expose to you the ability to create new timeframes.

[ktf]

(I thought you were using the RawDeviceService, in which case you can of course grab it when you create the callback).

[knopers8]

snapshot(), to be exact. But yes, the next processing step (checkers) was supposed to be inside DPL as well.

[ktf]

Ok, I will expose to you the ability to create new timeframes as well.

[knopers8]

Thanks!

[ktf]

Can we consider this done?

[knopers8]

As far as I remember, there was one issue left - some incomplete data would be dropped when booking a timeslot for the timer. You mentioned you could tackle it by creating a separate cache for timer timeslices or by making the cache a list instead of a round-robin vector.