Log4J Composite Configuration

[rkoshak]

When I upgraded to 2.5 M2 I noticed that I had a ton more logging statements in openhab.log from usual. I had some customization in org.pax.logging.cfg which thankfully didn't get overwritten and therefore I missed some additions to the file. What would be really nice is if I could maintain my own customization to the logging in /etc/openhab2/services or the like and the OH provided one imports it.

This got me to thinking and I did somewhat of a deep dive into OPS4J Pax Logging, Log4j2, and Karaf. I believe this is possible. I believe it's possible if we switch to an XML config (see https://svn.apache.org/repos/asf/karaf/site/production/manual/latest/log.html under Log4j v2 support) as we can then use XInclude to import the files. It is supposed to be possible using .properties files too (https://logging.apache.org/log4j/2.x/manual/configuration.html#CompositeConfiguration) but I could never get it to work and couldn't find any examples to help. I wonder if there is something in Pax that breaks the log4j.configurationFile property.

Before I spend any more time on this, if I cannot in the end figure out how to make this work using the current .properties files, would a PR that converts the config to XML be accepted? Obviously, if I can make it work with properties files I'll stick with that to have less disruption.

[mhilbush]

See #516. There's already an issue for this. And, there's even bounty on it! 😉

[rkoshak]

I swear I searched. I must have used the wrong words. Thanks! I'll move over to that issue.