implement a way to filter fields by name on log json formatter

[bnjjj]

This is a WIP PR to have your feedback

Motivation

I recently needed to filter fields from json logs, especially because sometimes for some logics in our own exporters we put some specific fields on spans and logs. But these fields are only useful for logic stuffs, they doesn't add any useful information for the users. So I looked over your documentation but was only able to find a way to filer the entire event based on fields and not filter fields from an event (log).

Solution

Implement the method filter_fields_by_name method for json formatter.

Example:

let subscriber = subscriber()
            .flatten_event(false)
            .with_current_span(true)
            .with_span_list(true)
            .filter_fields_by_name(|field_name| field_name != "answer" && field_name != "test");

[davidbarsky]

hi! i'm sorry for the delay in reviewing this. here's some general feedback:

1. in general, please point PRs at the master branch instead of v0.1.0! We'll handle backports.
2. I don't really want to add behavior to just the JSON formatter (in this this, filter_fields_by_name) that doesn't apply to other formatters. We already have a lot of divergence between formatters, and I don't want to add something as big as this.
3. Instead of this approach, I wrapping Json and JsonFields in another FormatFields or Visitor that is capable of filtering out fields you're not interested in. This has the nice side-effect of being generalizable to other formatters (if you're interested, we'd accept this change!)

[hawkw]

You may want to look at issue #73, which proposes a more general solution like what @davidbarsky's describing in #2353 (comment).

[bnjjj]

Thanks ! I will take a look and update the code :)

[bnjjj]

Ok @hawkw and @davidbarsky thanks for your feedback. I already wrote a small FieldFilter visitor. If you have time to take a look at this implementation that would be great. I will continue my work on this by implementing helper methods on Format to be able to use it directly on Format. Tell me if I'm wrong :)

[bnjjj]

Regarding my message on discord here do you have an idea on how I could properly implement it for json format @davidbarsky and @hawkw ? THanks a lot

[synek317]

The link to the discord discussion is no longer working. Is there still interest in implementing this feature? Could I try to help with that?