Automatic log file management with logrotate

Introduction

Logrotate is a popular log rotation utility that, according to its authors, "allows for the automatic rotation compression, removal and mailing of log files. Logrotate can be set to handle a log file daily, weekly, monthly or when the log file gets to a certain size.". It's available for most Linux distributions as a package, or you can build it from source here: https://github.com/logrotate/logrotate

Chances are, you already may have logrotate installed!

Configuring

Look in /etc/logrotate.d/

The above directory is the most common directory where logrotate looks for customized configurations for different software installed on your system.

Create a new file there, eg. guerrilla Then begin editing your configuration by changing the following to your preferences:

/home/gmail/*.log {
    daily
    size 200M
    rotate 3
    compress
    missingok
    notifempty
    create 0644 gmail gmail
    su gmail gmail
    postrotate
        kill -USR1 `cat /var/run/go-guerrilla.pid`
    endscript
}

Where:

• /home/gmail/*.log - is the location of the log files. * is a wildcard.
• daily rotate after a day
• size or, rotate after 200M or any size you choose.
• rotate 3 - leave 3 days of logs
• compress gzip old files
• missingok don't complain if log file is missing
• notifempty don't rotate if empty
• create create new files with mode, owner, group permissions
• su Use this user to perform all actions

The secret sauce above is the postrotate ... endscript section. This tells go-guerrilla to re-open the log files after they have been rotated. Make sure to change /var/run/go-guerrilla.pid to the file where go-guerrilla writes out the pid (process id).

Save and run it to see if it works:

$ logrotate /etc/logrotate.conf

It may barf at the beginning that it can't compress, but that should be OK.

check status like this:

$ cat /var/lib/logrotate/status 

RTFM ;-)

Check out the logrotate manual for a complete list of options and examples: http://linuxcommand.org/man_pages/logrotate8.html

Implementation details and limitations

Log file re-opening is triggered by listening to the USR1 [Unix signal] (https://en.wikipedia.org/wiki/Unix_signal) - therefore it will only work on systems following POSIX. Windows users may try using Cygwin which supports the kill command or the new Windows Subsystem for Linux

When using go-guerrilla as a package, it will not listen to any signal. It would be your choice on how to best capture an event and then deal with the event (call the log re-opening functions, etc). There's a handy helper function on AppConfig that can fire all the events for you:

func (c *AppConfig) EmitLogReopenEvents(app Guerrilla)