MongoDB Server Log to file and rsyslog
I found a solution where i configure rsyslog to pick up that file and forward it to my target server.

# RSyslog Configuration for MongoDB /etc/rsyslog.d/mongod.conf
$ModLoad imfile
$InputFileName /var/log/mongodb/mongod.log
$InputFileTag mongodb
$InputFileStateFile mongodb-state
$InputFileFacility local3
$InputRunFileMonitor
local3.* action(type="omfwd" target="target" port="514" protocol="udp" action.resumeRetryCount="100" queue.type="linkedList" queue.size="10000")


Based on:
https://www.rsyslog.com/sending-messages-to-a-remote-syslog-server/
and
https://serverfault.com/questions/396136/how-to-forward-specific-log-file-outside-of-var-log-with-rsyslog-to-remote-serv