Noticed this while investigating T181995: Port nutcracker statistics to Prometheus, silver syslog is full of upstart restarting nova-novncproxy:
Jan 5 09:56:21 silver kernel: [17078092.289489] init: nova-novncproxy main process (9854) terminated with status 1 Jan 5 09:56:21 silver kernel: [17078092.289508] init: nova-novncproxy main process ended, respawning Jan 5 09:56:21 silver kernel: [17078092.916135] init: nova-novncproxy main process (9871) terminated with status 1 Jan 5 09:56:21 silver kernel: [17078092.916152] init: nova-novncproxy main process ended, respawning