Pushing kea-dhcp4 server logs to different files based on severity

Unable to isolate kea logs based on severity level.

 "Logging": {
    "loggers": [
      {
        "name": "kea-dhcp4",
        "output_options": [
          {
            "output": "/var/log/kea-dhcp4.log"
          }
        ],
        "severity": "WARN"
      },
      {
        "debuglevel": 99,
        "name": "kea-dhcp4",
        "output_options": [
          {
            "output": "/var/log/kea-debug.log"
          }
        ],
        "severity": "DEBUG"
      }
    ]
  }

Above is the portion of kea server config, all the logs are directed to "/var/log/kea-debug.log" irrespective of severity level. Expected: logs of severity "WARN" and higher to be logged to "/var/log/kea-dhcp4.log".

Solution

From a quick reading of Section 18 of https://jenkins.isc.org/job/Kea_doc/guide/kea-guide.html, I would:

Try to put the debug log section before the warn log section to see if only warnings get logged.
Check the keactrl configuration.

It would appear that you can only have one log per "name" and that if you want debug logging, you would have to use a different logger name, eg. "kea-ctrl-agent" instead of "kea-dhcp4" - but it's unclear if there's a hierarchy involved and if that will catch entries of parts below it.

It should be easy to fix for the developers if it is the case - you should update the bug report in the kea project, here: https://gitlab.isc.org/isc-projects/kea/issues/592

Some other things that you could do is to log everything to syslog, and send it to a remote log and use something like splunk or logzilla to sort them by severity.

Or you if it's just temporarily, you could create a cron job that does this every few minutes, or just run it on a tail:

tail /var/log/kea-debug.log|egrep '(WARN|ERR|FATAL)' /var/log/kea-debug.log|tee -a /var/log/kea-dhcp.log

Assuming those words are present in the debug log, when those severities pop up.