Traffic Monitor truncates log file when restarted

[rawlinp]

I'm submitting a ...

• bug report

Traffic Control components affected ...

• Traffic Monitor

Current behavior:

TM truncates its log file upon startup:

[root@foo log]# ll traffic_monitor.log
-rw-r--r-- 1 root root 3107262 Mar  4 09:11 traffic_monitor.log
[root@foo log]# systemctl stop traffic_monitor
[root@foo log]# ll traffic_monitor.log
-rw-r--r-- 1 root root 3107262 Mar  4 17:02 traffic_monitor.log
[root@foo log]# systemctl start traffic_monitor
[root@foo log]# ll traffic_monitor.log
-rw-r--r-- 1 root root 704 Mar  4 17:02 traffic_monitor.log

Observed on 5.0.0 with the following logging config in traffic_monitor.cfg:

        "log_location_event": "/opt/traffic_monitor/var/log/event.log",
        "log_location_error": "/opt/traffic_monitor/var/log/traffic_monitor.log",
        "log_location_warning": "/opt/traffic_monitor/var/log/traffic_monitor.log",
        "log_location_info": "null",
        "log_location_debug": "null",

Expected behavior:

Traffic Monitor should not truncate its config upon startup. Instead, it should append to the existing log file.

Minimal reproduction of the problem with instructions:

Restart Traffic Monitor with the above configuration.