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Is this a bug? Blank custom property alert behavior.

klc2009

I have node custom properties where the value determines the alert actions. However, this property is not valid on some nodes so the value is blank. If I set an alert so that it fires if CustomPropertyXYZ<>somevalue, the nodes where the property is blank do not fall into that category.

For instance, I have a custom property called Carrier. For some of the WAN routers, I have this set to CenturyLink. But on servers and such it is blank. A Node Down situation for WAN routers requires that we follow a certain process, so I have a special alert that looks for Carrier is equal to CenturyLink. The server Node Down situations follow different processes, so I had a separate alert set to look for Carrier<>CenturyLink. However, this alert does not work when Carrier is blank.

I have resolved this by changing the alert to look for Carrier is empty, but it seems to me that intuitively looking for <> a specific value should encompass blank values as well. Perhaps this is faulty thinking on my part, so I'm looking for feedback.

Thanks!

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tomas.mrkvicka

Hi,

this is probably related to SQL meaning of operator "not equal" and NULL. If some column has NULL value (blank) then comparison this column to any value is always defined as FALSE. Sometimes it can be weird for people outside database world.

If you set it to condition 'is empty' (what you have done) it is equal to compare to NULL. Usually best way how to do such conditions is to do combined condition for emptiness and also for difference from given value.

netlogix

I am pretty sure it is the SQL thing, adatole wrote something like it in this. he used "is empty":

Where ANY of the following are true  Where ALL of the following are true     ALERT_CPU is empty     CPU_LOAD is greater than 90  Where ALL of the following are true     ALERT_CPU is not empty     the field CPU_LOAD is greater than the field  ALERT_CPU

shuth

I just came across the same issue when trying to create a similar set of alerts. As with the OP, it seems intuitive to me that a "not equal to" would include blank fields.

We have an interface custom property that can have various strings (WAN, etc). The aim for the alerts is; if the property = WAN and interface goes down then perform action ABC with higher priority values, and for all other values perform actions DEF. There is also an additional check against a node custom property.

The first version of the alert wouldn't trigger for interfaces with a NULL value in the custom property. The alternate alert using "is equal to WAN" works using this format.

Where ALL of the following are true

Interface status is Down

InterfaceCustomProperty is not equal to WAN

Where ANY of the following are true

NodeCustomProperty = UVW

NodeCustomProperty = XYZ

This version, which includes a check for the NULL values, does:

Where ALL of the following are true

Interface status is Down

Where ANY of the following are true

InterfaceCustomProperty is not equal to WAN

InterfaceCustomProperty is empty

Where ANY of the following are true

NodeCustomProperty = UVW

NodeCustomProperty = XYZ

We thought about using an "IS_WAN" true/false custom property as we could use a true/false in the alert but this custom property already identifies the WAN interfaces and includes other strings - it seemed repetitive to also set a second property each time a WAN interface is configured. However, I'm always open to ideas for improving/streamlining the system.