How can I set a field to null in kapacitor?

#1

Is it possible to set a field value to null, that will be written back to Influx as a null field value in the database?
Basically I have some logic that I want to work like this:

lambda: if (“x”==0, ‘null’, float(num/x))

I’ve tried various things but the closest I can get results in errors like this:
error calling “if”: Different return types are not supported - second argument is string and third argument is float64

Any suggestions?

#2

No, this is not possible. Currently lambda expressions do not support any kind of null type. What is the larger use case?

#3

I’m creating a new summary metric in a streaming task that is the result of dividing two other metrics, and then writing it back to a new measurement. If the divisor is 0 I want to write null there. Maybe I can find a way to simply exclude that metric in that case, which will probably have the equivalent result.

#4

I got a very similar issue where i use the percentage example to calculate rate of events. Sometimes there is no result for my queries because there were no results and therefore my division fails. Is there a way to handle such empty query results in the evaluation?