The frr.log file is empty after rotating log

[secretdeveloperisme]

Description

I have set up the FRR to ensure that all daemon processes, such as zebra, ospfd, bgpd, etc., log their output to the /var/log/frr.log file. However, I've observed that whenever logrotate performs its rotation on frr.log, the newly created file is empty.

Version

The issue is present in version 8.3.1 and may also occur in newer versions.

How to reproduce

1. Configure the daemons such as zebra, bgpd, osfpd... log into the /var/log/frr/frr.log file
2. Waiting for the rotation log
3. Check content of the frr.log file

Expected behavior

After rotation, the newly created file is no longer empty.

Actual behavior

the frr.log is empty

Additional context

Upon examining the /etc/logrotate.d/frr file, I found the following configuration:

/var/log/frr/frr.log {
    notifempty
    missingok
    postrotate
        /bin/kill -HUP `cat /var/run/*syslog*.pid 2> /dev/null` 2> /dev/null || true
    endscript
}

Currently, the postrotate script only sends the HUP signal to syslog. Should we be sending the USR1 signal instead to inform the daemons that are utilizing frr.log?

Checklist

• I have searched the open issues for this bug.
• I have not included sensitive information in this report.

[eqvinox]

Currently, the postrotate script only sends the HUP signal to syslog. Should we be sending the USR1 signal instead to inform the daemons that are utilizing frr.log?

Yes, that's exactly what would cause this, without USR1 to the daemons they keep logging to the previous file so the new one will remain empty.

The logrotate config shipped with FRR is intended for the "default" log syslog config, it needs the exact change you're describing to work with log file.

P.S.: 8.3 is really old at this point; we fixed at least one other issue where old logs were being kept open that might still be a problem in 8.3. If you see the old files being held open and/or still being logged to, you'll need to either update or manually backport fixes (as 8.3 is way out of community support…)

[secretdeveloperisme]

I think the issue may occur in lasted version because the file redhat/frr.logrotate is very similar with 8.3.
Should we update the file in source code or provide document to help user update it manually?