Plans to support trace-based exemplar filter?

[angelodipaolo]

Hello!

We've recently implemented metric and trace signals at eBay and are interested in using trace-based exemplar filters. Our Android partners are utilizing this filter but we noticed there is not yet support for this in opentelemetry-swift. Is there any plan to implement this in the near future?

We would love to help contribute to add support for this, but I'm not entirely sure how to approach the implementation. Based on Java's implementation, I see a filtering decision is made based on the context of the meter but ExemplarFilter does not have a context parameter. I'm wondering if it's just a matter of checking if the active span is sampled?

I also notice that StableMeterProviderBuilder does not allow for setting the filter, which seems like a simple change to make.

Any information or guidance you folks could provide would be much appreciated. We're willing to help add support but will need some direction.

Thanks!

[bryce-b]

It looks like the ExemplarFilters were partially implemented. I think it was unintentionally overlooked when the stable metrics were initially implemented. I'm reviewing it now and I'll layout what needs to get done to make it complete. If you're willing to help out, that would be greatly appreciated. Once I figure out what needs to get done maybe you can take a look and see if there are any tasks you can pick up?

[angelodipaolo]

Once I figure out what needs to get done maybe you can take a look and see if there are any tasks you can pick up?

Yes, I would be happy to pick up tasks to help out. Thanks!