The personal blog of Paul Krohn, writing in San Francisco.
My sweet wife has procured for me for my birthday — today for you ungrateful laggards — a set of Klipsch speakers. They sound dynamite (to my untrained ear) and have an iPod dock built in. I’ve elected to set them up in the kitchen, so we can listen to music while we cook. Which is great because to me that is the most romantic part of dinner.
A bit ahead of myself with the cacti post, the first job was to properly enable SNMP on all my computers, including the Macs.
You would think it was as simple as setting SNMPSERVER=-YES- in /etc/hostconfig and add a read user, and you would be partly right. That would make snmpd run and answer on port 161. However, there are some important limitations in the snmpd shipped with OS X.
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I’ve been struggling over the past couple weeks to get cacti to behave. It’s a pretty fully-featured monitoring system that can peek at SNMP or other data and graph it.
Anyway this is for those who already know what cacti is. I managed to do somehting I thought (maybe is?) pretty basic: graph the usage of something. The wrinkle was that in this case (swap usage) the SNMP MIB reports swap defined and swap available; what I wanted was swap used, particularly since on some systems (ie Mac OS X) swap space is assigned dynamically, and it would not be clear on a long graph how much swap was in use if the display is only of defined (allocated) and available.
It seemed pretty easy at the start but I got my brain tie in knots around data and graph templates. The easy part was just making a graph of the data presented. The trick was to make cacti display the syntax it was using — and errors it was generating — to make graphs based on the RRDTool databases. Use the ‘Turn on Graph Debug Mode’ button! It is very helpful.
Just at the moment I’ve opened every application on my Mac to try to consume all the available memory and make it allocate some swap space, to no avail … so I am starting to wonder if my graph actually does what I think it does?
Anyway give it a whirl and let me know if you get good results.
yah, got the first post on my own blog! way to go! I have alpha transforms and everything.