MDC-like contexts

[prepor]

Hello.

How about support of MDC-like (https://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/MDC.html) log's contexts? It's especially useful with structural log-appenders (like Graylog or Logstash).

[ptaoussanis]

Hi Andrew, could you give me some idea of how you'd like to see this implemented (or the kind of API you'd like to see)?

Am juggling quite a few things right now, so the more info you can give me the more likely I'll be able to help out.

Cheers! :-)

[prepor]

So. I don't have any interesting ideas about context. Just naive with-context macro with binding inside. It sucks with async code, but in modern world we have core.async with bindings support (as i know).

[ptaoussanis]

Closing for now. Between the log-config support and the relative ease of using custom dynamic bindings without Timbre's assistance, I think we're probably okay here? Feel free to reopen if you disagree. Cheers! :-)

[eoliphan]

Given that it looks like some of log-config's features are now in timbre itself, would it make sense to have this in timbre now?

Where with-context (or some alternative) merges the map arg with the existing parent value?

[ptaoussanis]

@eoliphan Hi Erich, with-context was added back in 2015: https://github.com/ptaoussanis/timbre/releases/tag/v4.0.0 :-)

[eoliphan]

Hey yeah, that's what I was referring to :). As it stands, I guess with-context is more like an NDC? The current value is the innermost context. I was looking at more MDC like behavior where the current context is the sum/union of all parents. For example:

(log/with-context
  {:outer :context}
  (log/info "outer")
  (log/with-context
    {:inner :context}
    (log/info "inner")))
; outputs
{... "context":{"outer":"context"} ...}
{... "context":{"inner":"context"} ...}

You'd want the map with both the :inner and :outer keys in the second one.

So basically a variant where the binding statement sets *context* to (merge *context* ~new-context)

[ptaoussanis]

@eoliphan Hi Erich, in that case I think you're probably looking for #262.
There's been a couple requests for that now, so I'll re-open it.

[ptaoussanis]

Addressed with 858830a