there should be some runtime way to control zabbix daemon operations - either by sending signals or some other means.

obvious use cases involve :
1. runtime debuglevel switching (improved debugging at ZBXNEXT-136);
2. configuration cache forced re-read (ZBXNEXT-816);
3. configuration file reload - ZBXNEXT-3162
4. forced passive proxy configuration sync - ZBXNEXT-1580 (available for active proxies)
5. item check update (before scheduled time) (passive - ZBXNEXT-473,ZBXNEXT-653; active - ZBXNEXT-810)
6. initiate housekeeper (ZBXNEXT-207)