keep $field [$field2 ...]
Only keeps certain fields in the message. All fields that are not specified in arguments are removed.
Example config:
from timer;
dump 'BEFORE> ';
keep $date $payload;
dump 'AFTER> '
Example output:
BEFORE> #7
BEFORE> $date=2020-02-20T17:25:55+03:00
BEFORE> $from=beholder://timer
BEFORE> $payload=A large hedgehog entered the building
BEFORE> $program=beholder
AFTER> #7
AFTER> $date=2020-02-20T17:25:55+03:00
AFTER> $payload=A large hedgehog entered the building