MongoDB log file growth

Question

Currently my log file sits at 32 meg. Did I miss an option that would split the log file as it grows?

Answer 1

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
}

Answer 2

If you think that 32 megs is too large for a log file, you may also want to look inside to what it contains.

If the logs seem mostly harmless ("open connection", "close connection"), then you may want to start mongod with the --quiet switch. This will reduce some of the more verbose logging.

Answer 3

Using logrotate is a good option. while, it will generate 2 log files that fmchan commented, and you will have to follow Brett's suggestion to "add a line to your postrotate script to delete all mongod style rotated logs".

Also copytruncate is not the best option. There is always a window between copy and truncate. Some mongod logs may get lost. Could check logrotate man page or refer to this copytruncate discussion.

Just provide one more option. You could write a script that sends the rotate signal to mongod and remove the old log files. mongologrotate.sh is a simple reference script that I have written. You could write a simple cron job or script to call it periodically like every 30 minutes.