support for SLF4J Markers

[dfa1]

Tentative implementation for:
quarkusio/quarkus#15193

The idea is to allowing passing SLF4J Marker as metadata in slf4j-jboss-logmanager:

 private void log(final Marker marker, final java.util.logging.Level level,  final String fqcn, final String message, final Throwable t, final Object[] params) {
        final ExtLogRecord rec = new ExtLogRecord(level, message, ExtLogRecord.FormatStyle.NO_FORMAT, fqcn);
        rec.setThrown(t);
        rec.setParameters(params);
        rec.setMetadata(marker); <--- todo
        logger.logRaw(rec);
    }

Then Slf4jLogger should be changed to fully implement the SLF4J logger interface (i.e. removing MarkerIgnoringBase).
The constraint is that metadata must be typed as java.lang.Object (to avoid strong and direct dependency to slf4j-api).

[dfa1]

Hi @jamezp!

any suggestion, idea or comment is welcome! :-)

[dfa1]

@jamezp I would like to provide the PR for slf4j-jboss-logmanager too (as mentioned in the initial comment). Do you see any problems with this approach?

NB: this method could be reused for log4j Marker too (https://logging.apache.org/log4j/2.x/log4j-api/apidocs/org/apache/logging/log4j/Marker.html)

[jamezp]

@dfa1 Sorry for the delay on this. AIUI markers are used more for log managers right? If so I'm not sure how the JBoss Log Manager will be able to use without it's own API.

That said Quarkus itself uses a fork of this log manager which is diverged at this point. The PR might be of more use there for you.

[dfa1]

no worries, you're already mentioned that you were busy... :-)

The idea is that the SLF4J binding should be able to create a ExtLogRecord without losing the marker instance provided by the client. Then, in the JsonProvider it could be used as:

@Singleton
public class MyJsonProvider implements JsonProvider {

    public void writeTo(JsonGenerator generator, ExtLogRecord event) throws IOException {
          if (event.getMetadata() instanceof Marker) { 
               // special logic here
          }
    }
}