If you're sending logs out to the host's syslog, then the log creator is your syslog daemon.

Also, processes in containers exist as processes on the host (they have different PIDs inside and outside of the container due to PID namespacing); so logrotate should be able to send signals to containerized processes.

hey thanks for that comment - could you talk about it in a slight more detail.

I have rsyslog on the host and I'm sending logs to host syslog through bind mounting of /dev/log . Is this what you meant by sending out logs to host ? I'm having a lot of trouble figuring out how to do it any other way.

Could you also confirm that rsyslog on host will be able to send appropriate signals to the container's syslog ... which forwards it to the containerized process ? I'm unable to find documentation in rsyslog (or syslog-ng) that talks about this behavior so I'm not sure.

No signaling needed other than rsyslog itself.

Sighup is needed when processes (such as Postgres) write directly to log files. These files are open, and when you want to rotate the file, you have to tell the process to close the files so that it will start writing to a new file.

If you tell Postgres to log to rsyslog (or any other syslog daemon), the log data will be sent to rsyslog via UDP, TCP or a Unix socket. Postgres itself will not have any files open, so there is no need to sighup it.

You will have to sighup rsyslog in the host system, though.

If you bind mount /dev/log of the host into your container, you only run rsyslogd on the host. There's no need to send any SIGHUP to anything in the container.