Log rotation

Logs produced by the API grow quickly and lead to very large files. Configure logrotate so a fresh log file is created every day and old ones are pruned automatically.

Docker users

If you run Kitsu through the official Docker image, logs go to the container's stdout and are handled by your Docker logging driver — you don't need any of the steps below. This guide is for bare-metal / systemd installs.

Store the PID of the zou processes

logrotate needs each Gunicorn process' PID so it can signal it to reopen its log files after a rotation. Have systemd create a runtime directory on boot and write the PIDs there.

Edit the zou unit file (/etc/systemd/system/zou.service) and add a RuntimeDirectory line before ExecStart:

RuntimeDirectory=zou

Then append -p /run/zou/zou.pid to the ExecStart line, for example:

ExecStart=/opt/zou/zouenv/bin/gunicorn -p /run/zou/zou.pid -c /etc/zou/gunicorn.py -b 127.0.0.1:5000 zou.app:app

Do the same in the zou-events unit file (/etc/systemd/system/zou-events.service), using a distinct PID file:

-p /run/zou/zou-events.pid

Reload systemd and restart the services so the changes take effect:

sudo systemctl daemon-reload
sudo systemctl restart zou zou-events

The PIDs are now written to /run/zou/zou.pid and /run/zou/zou-events.pid.

Configure logrotate

logrotate is a standard Unix tool that rotates logs for you based on a configuration file. Create /etc/logrotate.d/zou:

/opt/zou/logs/gunicorn_access.log /opt/zou/logs/gunicorn_error.log {
    daily
    missingok
    rotate 14
    notifempty
    nocompress
    size 100M
    create 644 zou zou
    sharedscripts
    postrotate
        kill -USR1 `cat /run/zou/zou.pid`
    endscript
}

/opt/zou/logs/gunicorn_events_access.log /opt/zou/logs/gunicorn_events_error.log {
    daily
    missingok
    rotate 14
    notifempty
    nocompress
    size 100M
    create 644 zou zou
    sharedscripts
    postrotate
        kill -USR1 `cat /run/zou/zou-events.pid`
    endscript
}

What the directives do:

Directive	Effect
daily	Rotate once a day
rotate 14	Keep the last 14 rotated files
size 100M	Also rotate as soon as a file exceeds 100 MB
missingok	Don't error if a log file is absent
notifempty	Skip rotation when the file is empty
nocompress	Keep rotated files uncompressed (set compress to gzip them)
create 644 zou zou	Recreate the log with these permissions and owner
sharedscripts	Run postrotate once for the whole block, not per file
postrotate … kill -USR1	Tell Gunicorn to reopen its log files

Save disk space

Replace nocompress with compress to gzip rotated logs. This trades a little CPU at rotation time for much smaller archives.

Verify

Dry-run the configuration to confirm it is picked up correctly:

logrotate /etc/logrotate.d/zou --debug

You're done with log rotation!