In it's simplest realization, one can implement NGINX log rotation as following:

mv access.log access.log.0
kill -USR1 `cat master.nginx.pid`

My question. Do we have a concurrency issue here? I mean, if NGINX writes a log entry between two actions (1) file was renamed and (2) it got a command to reload, could some of log entries be just lost?

  • if it helps to you, please mark the answer as complete – Anatoly Jul 13 '15 at 17:28
  • 1
    @mikhailov Sure. Tnx for helping out! – user1065145 Jul 14 '15 at 6:34

Before send USR1 signal wait for 15 seconds and you will see that *access.log.0" is still being used. It happens because log is open for write access based on inode, not the file name. So it is concurrent-safe to use this technique: mv + USR1

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