caddyhttp: Support multiple logger names per host

[francislavoie]

Context: https://caddy.community/t/config-cleanup-for-logging-blocking-and-a-signalr-issue/22643

I realized that there's currently no good way to point a specific hostname to write to more than one logger at once, because logger_names is a simple map[string]string (so only one value per key).

To solve this, I'm deprecating logger_names and adding a new logger_mapping (which Caddyfile immediately uses) I'm changing logger_names to be a map[string]StringArray which is a type which accepts either a JSON string or array (where a string gets turned into a one-element string slice). Then, I reworked the logging code in the server to loop over the list of wrapped loggers.

I'm not 100% convinced about the logger_mapping name... I'd rather reuse logger_names, but obviously we can't do that, it would be a breaking change. Any better naming ideas? Resolved by doing custom JSON unmarshaling.

[mohammed90]

I'd rather reuse logger_names, but obviously we can't do that, it would be a breaking change. Any better naming ideas?

We can do custom unmarshaling by implementing the JSONUnmarshal (or is it better to use TextUnmarshal? 🤔) method. In it we'll check if it can be marshalled into a map[string][]string or map[string]string, reporting a warning when marshalling into a map[string]string.

[francislavoie]

I guess so. 🤔 Most of the time that approach feels wrong but in this case it can be transparent so it's probably fine.

[francislavoie]

Thanks for the idea @mohammed90! Much better I think.

[francislavoie]

The user tried it out and confirmed it resolves their usecase:

https://caddy.community/t/config-cleanup-for-logging-blocking-and-a-signalr-issue/22643/12

[mohammed90]

Thanks for the idea @mohammed90! Much better I think.

Great 😃 I have to update the nginx-adapter after this PR

[mholt]

This looks quite complicated to me 🙈 but if it works and is useful for real world use cases, I guess that's how it goes (my fault for the logging design). Thank you for the tricky patch!!