[ActiveRecord] Add Attributes for Async Queries

[arielvalentin]

ActiveRecord 7.1 introduced async query methods¹, which leverages concurrency primitives via Promise API to defer executing queries.

We would like to enrich ActiveRecord related spans to know whether or not they were executed from the async context.

Additional Notes

The sql.active_record notification payload includes a async attribute:
https://github.com/rails/rails/blob/616d3a7675c18ae2d38d3116de47e2e7308cfbd8/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb#L1135

We may be able to enrich the ActiveRecord span and amend it as a Shared DB attribute for the driver itself however we do not currently use notifications in this instrumentation.

Worst case scenario, we monkey patch existing async methods, concurrency primitives.

Footnotes

1. https://github.com/rails/rails/pull/44446 ↩

[bensheldon]

Thank you for opening this! 🙇🏻

It would also be great if we could include the lock_wait attribute too, which represents how much time is spent in the foreground waiting for the query to complete (in a true async query, it would be 0.0ms):

https://github.com/rails/rails/blob/df9912116b29423b5bde3771b9829447a07d3f6c/activerecord/lib/active_record/log_subscriber.rb#L23-L24