Calculated Item sum for lifetime

[hectorsaratoga]

Hello

I'm trying to create an item that stores the total number of hours the computers are on.

I have created a calculated item

key= total.hours
Fomula = last("total.hours")+diff("system.uptime")



But if it's the first time or it has no total value.hours gives an error.

"Cannot evaluate expression: "Cannot evaluate function "last()": item "pd2008:total.hours" not supported."



How can I store and add up all the hours that the item is active?

The idea is to add them to the inventory as too.


Thanks

[Hamardaban]

Your expression does not work because there is no initial value for this item.
And if it is not, then the last() function will not work and item will not work again.

Change the formula for example to 0+0, wait for the expression to trigger and write the value to the database, and then change the formula to your own.

Try searching the forum - this topic has already been discussed.

[Hamardaban]

Probably it would be more correct to use change()

[hectorsaratoga]

Thanks to all of you

Isn't there an option to set an initial value that can be automatic? With a macro you could?

modifying the formula manually every time a new host enters does not seem feasible to me.

I've been looking through the forum, but I didn't find anything that was automatic.

Thank you.

[Hamardaban]

Use preprocessing to write the initial value when an item error occurs

[hectorsaratoga]

I think I'm doing it wrong, I'm still failing. :-(

[hectorsaratoga]

I'm really going crazy, I've tried a thousand things and I don't get it

I don't understand what I have to do :-(




Expression

[Semiadmin]

Let that regex return whatever there is, but set "Custom on fail". That will set value to something you like, if there is no value at all and calculation fails...

It's a clever trick, but "Custom on fail" won't work. But maybe a new option "Check for not supported value" in version 5.2 will help.

[Hamardaban]

That's what I was talking about.

[cyber]

Yep, I should not write things, while on vacation.. Of course it won't help, if there is no value present...

[hectorsaratoga]

Thanks .

I'm in 5.0 :-(

So there's no way to do a sum a = a +b without failing the first time, no?

[hectorsaratoga]

Thank you all but it doesn't work for me either.


I don't know, after Christmas I'll come back to give it a thought but I think I'll have to do it with a local script. :-(

[cyber]

And diff() just tells you that there is a difference, not how big it is...

diff
Checking if last and previous values differ.		Supported value types: float, int, str, text, log Returns: 1 - last and previous values differ 0 - otherwise

[cyber]

Let that regex return whatever there is, but set "Custom on fail". That will set value to something you like, if there is no value at all and calculation fails...

[Semiadmin]

It works in 5.2.6 via "Check for not supported value" preprocessing.
But be careful: in early 5.2 minors, this trick leads to zabbix server restart.