Finding the way to log using Logback on error level using two different appenders. First one is the plain file, second one can be anything else. The purpose was to log using New Relic API. Existing appender can be extended and do whatwever you want. Proper filtering achieved using Groovy expressions.
jillukowicz/logback-newrelic-playground
Customised logback logger using different appenders (newrelic) on the same level
Shell