Parametrize tracing formatter

[adizere]

Summary

For our use-case in the relayer-cli crate (informalsystems/hermes#500) we would like to enable JSON-formatted tracing output. At first glance, it's not clear if abscissa permits this kind of configuration. Thanks in advance for any advice!

Description

Abscissa core is setting the global subscriber for tracing as follows:

abscissa/core/src/trace/component.rs

Line 40 in cbecf5f

tracing::subscriber::set_global_default(subscriber)

If I understand correctly, all applications built on abscissa are forced to use this subscriber. It would be great to allow more flexibility here. Note that documentation in tracing seems to provide guidance specifically against libraries using set_global_default.

[tony-iqlusion]

Yes, this would definitely be good.

For reference, how zebrad is managing its tracing config:

https://github.com/ZcashFoundation/zebra/blob/main/zebrad/src/application.rs#L220-L238

[adizere]

Thanks!

Just to note that this issue it not a priority.

We decided to use a custom solution instead of globally enabling JSON output. In the future, we may switch to a more principled approach, similar to the suggested zebrad solution to make all tracing output in JSON (minimal working example here).