It could be useful to have some events that are fired at certain points in the OpenNMS lifecycle, like:

• OpenNMS starts to start

• OpenNMS has finished starting

• OpenNMS has started to shutdown

• OpenNMS is almost done shutting down

Some of these may be useful for notifications (especially the starting up one), as that can help you know about unexpected restarts (for example, if OpenNMS crashes, but is restarted by Systemd).