MongoDB log file growth

You can use logrotate to do this job for you.

Put this in /etc/logrotate.d/mongod (assuming you use Linux and have logrotate installed):

/var/log/mongo/*.log {
    daily
    rotate 30
    compress
    dateext
    missingok
    notifempty
    sharedscripts
    copytruncate
    postrotate
        /bin/kill -SIGUSR1 `cat /var/lib/mongo/mongod.lock 2> /dev/null` 2> /dev/null || true
    endscript
}