After the upgrade to version 2.2.9 zabbix stopped working. It helped erase the history tables of values. After about a week the functioning of the problem recurs. In the log is no relevant information:

3835:20150323:104719.354 server #729 started discoverer #18
3834:20150323:104719.358 server #728 started discoverer #17
2276:20150323:104719.711 Got signal [signal:15(SIGTERM),sender_pid:3917,sender_uid:0,reason:0]. Exiting ...
2276:20150323:104721.714 syncing history data...
2276:20150323:104721.717 syncing history data done
2276:20150323:104721.717 syncing trends data...
2276:20150323:104721.815 syncing trends data done
2276:20150323:104721.815 Zabbix Server stopped. Zabbix 2.2.9 (revision 52686).
4383:20150323:105022.796 Starting Zabbix Server. Zabbix 2.2.9 (revision 52686).