Issue with calculated items missing

[nycnewman]

Seeing an issue with Zabbix 4.2. This was also an issue with 3.2 before upgrade. I monitor a printer via SNMP to get toner levels. Every day or so a calculated item in a template stops being calculated correctly and goes blank (no value shown in a graph of values). This triggers a failure which eventually auto-resolves when values returns to being calculated. The underlying SNMP values show correctly in a graph over the same period so it appears to be inly the calculated items that go missing.

What options are there to debug this? Is there a way to enable higher levels of debugging for calculation process to see whether this is a timeout, acahce value, file handle, etc type of issue.

This causes a lot of unnecessary noise and alerts which I would like to stop receiving. I have searched this forum and done many Google searches but not yet see a solution to this.

Thanks

[zux]

First check the item when it's not working, it should be unsupported. If it's unsupported, it should have a red icon in the configuration page
By clicking on the red icon, you should be able to see an error.
Also., try grepping the log for this item.

[nycnewman]

I see the following in the logs. Wasn't able to edit post before so couldn't add. Looks like the value goes unsupported for a while and then gets correct values. Clearly calculated item cannot get calculated and thus loses value. Not clear where the -2 value is coming from and don't see this a graph of the values for that item.

Edward

31081:20190812:201212.873 item "printer-nyc-xerox-c8030:ink.cyan.max" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31081:20190812:201212.873 item "printer-nyc-xerox-c8030:ink.black.max" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31081:20190812:201212.874 item "printer-nyc-xerox-c8030:ink.magenta.now" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31081:20190812:201212.874 item "printer-nyc-xerox-c8030:ink.cyan.now" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31081:20190812:201212.874 item "printer-nyc-xerox-c8030:ink.yellow.max" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31081:20190812:201212.874 item "printer-nyc-xerox-c8030:ink.yellow.now" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31081:20190812:201212.874 item "printer-nyc-xerox-c8030:ink.magenta.max" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31081:20190812:201212.874 item "printer-nyc-xerox-c8030:ink.black.now" became not supported: Value "-2" of type "string" is not suitable for value type "Numeric (unsigned)"

31080:20190812:201214.876 item "printer-nyc-xerox-c8030:yellow.cartridge.toner" became not supported: Cannot evaluate expression: "Cannot evaluate function "last()": item "printer-nyc-xerox-c8030:ink.yellow.max" not supported.".

31083:20190812:201226.892 item "printer-nyc-xerox-c8030:black.cartridge.toner" became not supported: Cannot evaluate expression: "Cannot evaluate function "last()": item "printer-nyc-xerox-c8030:ink.black.max" not supported.".

31081:20190812:201227.895 item "printer-nyc-xerox-c8030:cyan.cartridge.toner" became not supported: Cannot evaluate expression: "Cannot evaluate function "last()": item "printer-nyc-xerox-c8030:ink.cyan.max" not supported.".

31081:20190812:201238.917 item "printer-nyc-xerox-c8030:magenta.cartridge.toner" became not supported: Cannot evaluate expression: "Cannot evaluate function "last()": item "printer-nyc-xerox-c8030:ink.magenta.max" not supported.".

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.cyan.now" became supported

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.yellow.max" became supported

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.black.max" became supported

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.yellow.now" became supported

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.cyan.max" became supported

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.black.now" became supported

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.magenta.now" became supported

31080:20190812:201242.922 item "printer-nyc-xerox-c8030:ink.magenta.max" became supported

[nycnewman]

Further investigation suggests that occasionally SNMP may be returning -2 from device. This doesn't fit unsigned numeric causing item to go unsupported. This then has knock on effect for calculated values causing alarms to be generated.

Is there a best practice for how to handle this situation? Any thoughts on why a printer would return -2? Is this a know error condition?

[DaneTorson]

That you should check with printer manufacturer's documentation.
Here i found some ideas what to do if you receive negative values:
https://kb.paessler.com/en/topic/661...egative-values
Could be a result of integer overflow on the device for this SNMP value.
Another solution would be to check if this particular printer has firmware upgrade available.

[zux]

on version 4.2 you can use preprocessing step "in range"

[nycnewman]

Thanks. Will try that