Module io.jstach.rainbowgum.slf4j

module io.jstach.rainbowgum.slf4j
SLF4J 2.0 implementation.

Rainbow Gum SLF4J implementation supports:

There is no built-in Marker support (it is not stored on the event or used for routing/filtering by default), but a decorator can observe markers and act on them, e.g. surface one as a key value or filter on it.

Rainbow Gum supports key value pairs in LoggingEventBuilder by overlaying on top of the current MDC at the time the event is constructed and put into the events key values. The value parameter in LoggingEventBuilder.addKeyValue(String,Object) are converted to String immediately as only String values are supported at this time.

Rainbow Gum SLF4J implementation is unique in that it has two special implementation of loggers:

  • Level Logger - logger based on level threshold and can never change!
  • Changing Logger - level and other configuration can change.
Other logging implementations like Logback by default use something analogous to changing loggers which require a constant check if the level threshold has changed. Level loggers do not need to do that check. Unless changing loggers is turned on by default Level Loggers are used which are close to zero cost for discarding events.

The SLF4J API does not document nullability for MDCAdapter or LoggingEventBuilder.addArgument(Object) (see slf4j#493). Rainbow Gum accepts null more widely than SLF4J's own signatures require - e.g. MDC values, and logged arguments - for compatibility with existing SLF4J usage and other implementations, but this is not a recommendation: prefer not passing null where SLF4J itself gives no guarantee it is supported.

Like SLF4J's own reference LoggingEventBuilder implementation, Rainbow Gum's is mutable: each fluent call mutates and returns the same instance rather than a new one.

See Also: