<custom_id:1,custom_value:123> <custom_id:1,custom_value:123>
<custom_id:1,custom_value:456> -> unique by ${custom_id}->
<custom_id:2,custom_value:789> <custom_id:2,custom_value:789>
nifi queued distinct/unique by 'custom key'
mvn package
nifi.nar.library.directory=./lib
nifi.nar.library.directory.custom=./lib_custom
nifi.nar.library.autoload.directory=./extensions
nifi.nar.working.directory=./work/nar/
cp nifi-unique-nar/target/nifi-unique-nar-0.1.nar nifi/lib_custom/
nifi/bin/nifi.sh restart