I would like to be able to wait for, or execute, an item collect according to a pre-set rule on a "Master Item".

Examples:

1. ICMP Ping: no data can be collected when no connectivity is available, i.e uptime;
2. Ethernet Interface: no data can flow (if*Octects == 0) when the ifOperStatus is down;
3. FiberHome's ONU: `authOnuLastDown' and `authOnuLastDown' does not need to be updated if `GEPON-OLT-COMMON-MIB::onuStatus` is unchanged, but must be collected when `change(//onuStatus)<>0';
4. Huawei's ONU: `hwGponOntOpticalDdmRxPower', in dBm, is '2147483647' when the device is offline, but is correct when `hwGponDeviceOntControlRunStatus=1(up)';
5. Some SFP/SFP+/QSFP interfaces report a default value (0 dBm) when down, what affects the `avg()' signal calculations.

The preprocessing rules for the "Master Item" would be:

1. on change only: collect;
2. on value, on interval only: collect.

This rules can save resources, reduce queue size, also keeping data updated only when needed.

"Throttling is the exact thing that will allow you to drop repetitive values on a Pre-processing level and collect only changing values."

https://blog.zabbix.com/why-zabbix-throttling-preprocessing-is-a-key-point-for-high-frequency-monitoring/12364/