context support

[prepor]

Just suggestion for #42

[ptaoussanis]

Hi Andrew, thanks for this!

I may be misunderstanding the intention a little - what would we gain from making this a Timbre feature over, say, just doing this on the application-side?

Remember that appenders are just fns, so you could write an appender that checks+uses the state of a dynamic variable (like *context* here). Since appenders see raw arguments, it'd also be possible to provide context via logging arguments themselves: (timbre/infof "User logged in: %s" user-name {:user-id user-id}).

In that last example, the appender could be written to check appender args for a map with a :user-id key. (Or :context or whatever). You can see an example of this technique here: https://github.com/ptaoussanis/timbre/blob/master/src/taoensso/timbre.clj#L193 where some appenders will look for a map with a :timbre/hash key to decide whether two log entries should be considered "the same".

Let me know what you think, cheers! :-)

[prepor]

Anything can be done on application side :) In Timbre it can be "specification" for appenders. And appenders can handle this in their way as doing so in log4j-world with MDC and NDC. Contexts can be used in standard redis appender, and in future standard graylog and splunk appenders.

[ptaoussanis]

Hi Andrew, okay - I'd like a little time to think about this & possible alternatives. Your PR definitely helped clarify your objective, so thanks for that!

Will get back to you.

Cheers :-)

[prepor]

Thank you!

[hugoduncan]

FWIW, we ended up implementing something very similar, using middleware to add the value of a *context* var onto a :context key. https://github.com/palletops/log-config/blob/develop/src/com/palletops/log_config/timbre.clj#L49

[ptaoussanis]

Hi Hugo, looks good! Thanks for pinging about this.

Your library looks interesting too! Shall I perhaps link to it from the Timbre README, or is it something you're just using internally?

[hugoduncan]

I'ld be honoured if you linked it. At the moment we're just using this internally, but other users (and contributors) are definitely welcome. Also more than happy should any of the functionality end up in Timbre itself.

[ptaoussanis]

Okay great, just added a link :-) Haven't had a chance yet to look at it in detail, but would certainly be open to PRs that you think might be useful or better-integrated upstream.

Have a great weekend, cheers!