Metrics reader supports configuring aggregation and temporality

[kaylareopelle]

The metrics Reader implementation should support configuring the default aggregation and the default temporality on the basis of instrument kind. There are two lines on the spec compliance matrix about this.

This may be the relevant spec: https://opentelemetry.io/docs/specs/otel/metrics/sdk/#metricreader

Our aggregation classes set the temporality and it can be configured using an environment variable, OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE

Our instruments have a default temporality and don't have a public-facing API to change their aggregation. We should look at the configuration options for aggregation and temporality and see if they are compliant. If they are not, update the SDK to make it compliant.

[github-actions]

👋 This issue has been marked as stale because it has been open with no activity. You can: comment on the issue or remove the stale label to hold stale off for a while, add the keep label to hold stale off permanently, or do nothing. If you do nothing this issue will be closed eventually by the stale bot.

[zvkemp]

I can look into this.

[kaylareopelle]

Thanks, @zvkemp! I've assigned this issue to you. I know @xuan-cao-swi, has been working on something similar, with issue #1742 implemented in PR #1769.

It might be that the functionality is there, but we need to confirm it is aligned with the specification. The section in the specs that describes this environment variable is here (with a few references to another config outside the scope of this issue).

Let us know if there's anything we can do to help!

[zvkemp]

Ok, it seems like #1769 has been marked as targeting this issue specifically. I'll hold off for now, assuming that one will eventually be merged.

[xuan-cao-swi]

Hi @zvkemp , please do share your thought and code in same or different PR. I opened it as draft as I don't have 100% confidence about the approach I have taken ;)