The Zabbix Sender is meant to be periodically run, for example every few
minutes, and pushes all Zabbix items which have been accumulated in one ore
more spool files to the Zabbix server using the zabbix_send(1) command.
This was it is very easy to cope with multiple values, even from different sources, and not lose items when the system is offline or other errors occur: the Zabbix Sender retries sending out items until it succeeds.