Apply mathematical operations to |query...| ?

[Frances]

I'm displaying a piece of data that's being gathered in an SNMP walk as part of a data query as "input" (ungraphed) data. I'm attaching it to a graph template as a 'COMMENT' using a '|query|', but the appropriate method for applying mathematical operations to the figure is eluding me. In this case, I'm pulling a numerical value from the query and I'd like to divide that value by ten. It seems I'm either missing something embarassingly simple, or it just can't be done in 'COMMENT' statements (or) can only be done with "output" data. Help..? ;b

[pfarmer]

Hi Frances,

I'm trying to do something similar - I want to graph my traffic in/out for my router interfaces (which isn't a problem) and I've created a comment that tells the link speed (which also isn't a problem.)

However, the graphs I'm creating I want to use bytes, not bits, so I want to convert the ifSpeed value to bytes instead of bits .......

So I get a COMMENT of "Link speed: 32KB/s"

[JVandermark]

Just use the CDEF Function: /cacti/CDEF.php. You can add them and apply...

"out of the box" Cacti comes with "Turn Bytes into Bits" In your case you can just reverse this

[pfarmer]

Thanks JVandermark - I understand this and I've made a CDEF to convert bits to kilobytes (using the same method as the bytes to bits) but I can make it actually change the ifSpeed value.....

[Frances]

Hmm... If I recall correctly, I tried to use a CDEF for this, but wasn't able to get a CDEF to apply to "input" data. The trick is, the OID for this piece of data is found via a query, but the data is not expected to change once found, so I'm grabbing it as "input" rather than "output" data in the query. I could grab it as "output" data, but I don't have need to graph it, I just want it displayed.

[TheWitness]

I am contemplating a patch to support the parsing of |query_...| in both COMMENTS and HRULE/VRULE before I return to work on July 18th. I will be out of town until July the 9th however.

TheWitness

[interweave]

I was having the same problem, wanting to change the ifSpeed to Mbps.

I was getting "ERROR: rpn expressions without DEF or CDEF variables are not supported" if I did:

cdef=|query_ifSpeed|,1000000,/

Here's the CDEF I came up with:

cdef=CURRENT_DATA_SOURCE,CURRENT_DATA_SOURCE,-,|query_ifSpeed|,+,1000000,/


I take the current data and subract it from itself and add the result (which is 0) to the value returned by the query.

Works quite well.

Scott

[gandalf]

cdef=CURRENT_DATA_SOURCE,CURRENT_DATA_SOURCE,-,|query_ifSpeed|,+,1000000,/

Yep, ok. Reason for this is, that each CDEF must reference some DEF. Another approach may be

Code: Select all

cdef=CURRENT_DATA_SOURCE,POP,|query_ifSpeed|,+,1000000,/

Reinhard

[interweave]

Thanks Reinhard! I like your version better!

Scott