Configuration checks breaks freeform keys

[pieterlexis-tomtom]

Describe the bug
The Scalyr logger has 2 configuration settings (sessioninfo and attrs) that can contain arbitrary key-value pairs. This is extra information sent alongside the data. This is configured as follows:

    loggers:
    -   name: scalyr
        scalyrclient:
            apikey: XXXXX
            attrs:
                service: dnstap
                type: queries
            flush-interval: 10
            mode: flat-json
            sessioninfo:
                cloud_provider: Azure
                cloud_region: westeurope

When starting go-dnscollector, it errors (key name might differ, based on parsing order):

config error: unknown YAML key `cloud_region` in configuration

To Reproduce
Configure the scalyr logger as shown above, start go-dnscollector.

Expected behavior
go-dnscollector starts fine.

Additional context

• Version 0.43.0 and commit 0267e3b

These fields in the config are a map[string]string and a map[string]interface{}.

https://github.com/dmachard/go-dnscollector/blob/0267e3b47aa374b51df84ceacb61238258d3fdea/pkgconfig/loggers.go#L239-L240

Perhaps these field types should be ignored when converting the config to a map before checking it?

[pieterlexis-tomtom]

I had a look at the code and am not convinced this will be an easy fix, seem as how the keys are actually checked. It looks like the whole config checker might need a re-design :(

[dmachard]

I agree with you, the complexity of the config checker is too high, a complete redesign is needed. Any helps are welcome :)
In the meantime, I will push a quick and dirty fix :(

[dmachard]

FYI I have started a redesign of the config checker

[pieterlexis-tomtom]

Cool! Can you explain the design? Perhaps I can chime in with ideas or code :).