Proper way to rotate Nginx logs

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While the world is divided on whether the humble named pipe is friend or foe, it is probably the simplest solution to your problem. It does have a few drawbacks (in that you need to create the pipes ahead of time), but it eliminates the need for a cron and allows you to used the logging pipe-filter of your choice.

Here’s an example using cronolog on access.log:

  1. Pick a path for our named pipe. I intend to keep my logs in /var/log/nginx, so I’ll put my pipes there as well. The name is up to you; I append .fifo, and it’s access.log, so mine will be at /var/log/nginx/access.log.fifo.
  2. Delete the file if it exists.

  3. Make a named pipe for the logfile:

    mkfifo /var/log/nginx/access.log.fifo

  4. Configure nginx.conf to point the log at the pipe you just made:

    access_log /var/log/nginx/access.log.fifo;

  5. Modify your init.d script to start the log rotator listening to the pipe before we start the server:

    LOGS="/var/log/nginx"
pkill -f "/usr/sbin/cronolog --symlink $LOGS/access.log"
( cat $LOGS/access.log.fifo | /usr/sbin/cronolog --symlink $LOGS/access.log "$LOGS/%Y/%m/%d/access.log" ) &

    A similar commandline would be used for rotatelogs should you prefer it to cronolog — see their docs for the syntax.

    If your distrobution has a start-stop-daemon, you should be using that instead, as it theoretically has whatever special knoweldge about your platform there is, and taking care of pkill for you. Simply wrap the command in a script, and pass it as --exec to start-stop-daemon in your init.d/nginx.

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