SlowRequest logging disabled if SolrCore logger set to ERROR

If someone sets ROOT logger to ERROR, then SolrCore class will also be set to ERROR, and even if SolrCore.SlowRequest level is set to INFO, no logs will be written to solr_slow_requests.log.

Some debugging revealed that changing log level of SolrCore to WARN fixes it. This suggests that since SlowRequest is not a real class but just a logger name, it is still subject to the log level of SolrCore.

I suppose that the same will be true for SolrCore.Request logging.

One solution could be to create a real class for SlowRequest logging. Another solution could be to explicitly set SolrCore level in log4j2.xml so that it does not follow the ROOT level.