On Jul 27, 2006, at 5:56 PM, Matt Stevens wrote:
I'm writing a custom probe that's fetching some values from a
machine running NET-SNMP. NET-SNMP is returning the values as
strings, even though they're integers.
I'd like to graph the values (ie. PER-SECOND), but the only way I
can get them to show in my probe is to use the DEFAULT type. Which
then displays the values, but doesn't make them chartable.
Is there an easy way to get Intermapper to treat these values as
numbers - or convert them? Doing it in NET-SNMP requires me to do
quite a bit more work than the current method.
I sense there are two questions here. Your first question is how to
get InterMapper to treat values as numbers so you can chart them. By
default, string values are not chartable, and floating point numbers
(with a decimal point) have only the integer value charted. However,
in calculations, the context of the value determines how it is used...
To treat strings as numbers or chart floating point values with more
precision, you need to use the "chartable" macro in your <snmp-device-
display> section instead of the variable name:
${chartable: $str }
If you want to retain precision after the decimal point, you need to
tell InterMapper the decimal format using an optional argument:
${chartable: #.## : $str }
The value part of the chartable macro is a full-blown expression, so
you can pick apart a string using substr or unpack. e.g.
${chartable: substr( $str, 2) }
Your second question (possibly) is that you want to chart the deltas
of the values, rather than the values themselves. To do this with
string values, you need to add an extra step. You have to simulate
the calculation that PER-SECOND automatically does for you.
You'll need to add some CALCULATION variables, one to store the
delta, and the second to store the value of the previous/current
counter and timestamp. You'll most likely get $time from sysUpTime,
which is in hundreths of a second.
val_persec, ($val - $prev_val)/(($time - $prev_time) / 100),
CALCULATION, "intermediate calculation"
prev_val, $val, CALCULATION, "previous value"
prev_time, $time, CALCULATION, "previous time"
This works because all calculation expressions are evaluated top to
bottom in order, and InterMapper retains the results of all variables
between polls.
Regards,
Bill Fisher
Dartware,
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