https://community.cloudera.com/t5/Support-Questions/Drill-in-Nifi-DBCPConnectionPool-1-5-0-error-failed-to/m-p/222841#M184707 <P>I don't have much experience with Apache Drill, but looking at the source code, it looks like it fails at instantiating the class specified with 'hadoop.security.group.mapping' parameter. The parameter is usually defined at a Hadoop configuration file, 'core-default.xml'.</P><P>Are you aware of any configuration file specifying 'hadoop.security.group.mapping' parameter potentially being null?</P> Wed, 20 Jun 2018 19:01:52 GMT kkawamura 2018-06-20T19:01:52Z