Configure Java Util Logging bridge

[rjernst]

Elasticsearch uses log4j as its logger. java.util.logging may be used by some dependencies (eg Lucene now uses it in some places). Currently these log messages are captured by our stdout/stderr -> log4j because java.util.logging has a default implementation which writes to stdout/stderr.

log4j includes a bridge jar that configures java.util.logging to go directly to log4j logging. Using that bridge is superior to capturing the same log messages on stdout/stderr because it provides better control over muting classes or packages log messages. We should consider adding the java.util.logging bridge.

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[rjernst]

Note that one downside to this is it requires adding the JUL bridge jar to server. That would be a new jar which all plugins have access to. There are possibly ways to avoid that being exposed to plugins (classloader filtering).

[uschindler]

The jul bridge does not bring in any additional public apis. It is just glue code between log4j and jul. Actually it does not add anything useable to plugins. It could be hidden by class loader filtering, but who cares. The code is executed on a higher level.

[pgomulka]

I think it should be safe adding log4j-jul dependency, its api is very simple and is a subset of what log4j2 offers. https://github.com/apache/logging-log4j2/tree/2.x/log4j-jul

once we decide to migrate to ES logging API we could consider implementing a trivial bridge from JUL to es-logging-api, but for the time being log4j-jul is probably enough