Spans are not propagated to the log4j backend

[lukasz-golebiewski]

A reproducer is available here: https://github.com/lukasz-golebiewski/zio-logging-example

[lukasz-golebiewski]

Looks like the solution was to concat LogFormat.spans with the default SLF4J log format.

SLF4J.slf4j(LogFormat.spans + SLF4J.logFormatDefault)

Is there a reason why spans are not being logged in the default format?

[justcoon]

Hi @lukasz-golebiewski
I think reason for that is that LogFormat of core zio loggers
https://github.com/zio/zio-logging/blob/master/core/shared/src/main/scala/zio/logging/LogFormat.scala#L917-L922
also do not contains spans, so they were not added also to slf4j default format

[lukasz-golebiewski]

This is interesting, because an app extending ZIOAppDefault without overridden bootstrap, so using the default zio logger, does log spans out of the box