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glinks

Linux Kernel Stats in Go

This tool basically parses and presents all useful data I can find under /proc on Linux.

Fun with math

This originally started with gathering this sort of data via Sensu for Graphite. The Sensu plugins for checking CPU statistics are seriously flawed (eg. sensu-plugins-cpu-checks).

Basically they screw up sampling royally by polling the values, sleeping a second, polling again, and calculating over the 1 second interval. It's a completely accurate measure over that second, but you really want to sample the entire time from the last run.

Whawhat???

OK, so imagine you set the check interval at 10 seconds. Basically you're measuring only the first second out of every ten. Worst case you could have a workload that beats every ten seconds. The check is going to either show the highest workload if the check coincides with the work, or lowest workload if they're out of phase. The further apart the checks are, the less representative your 1 second sample is.

But it's not just this weird workload, any workload that fluctuates will be inaccurately measured and graphed even worse. The fact that it's being graphed assumes that the check needs to cover the duration since the last, not just the next second.

So why not fix their stuff?

So it goes back to the awesome sysstat package. I really just wanted to use the venerable sar and co. But their use is really intended to be interactive. I don't want to push the data from every host, I want to pull it and be able to change intervals on the fly.

So I could rewrite the Sensu plugin and do all this work in Ruby or something. But that just seems so single purpose. Plus I don't want to fire up an interpreter for something that I may need to run at a pretty high frequency.

I'm selfish

I also was just looking for a good excuse to use Go. I'd written toys, but this seemed like a good task for it.

• I want it to be compiled so I don't have interpreter/JVM overhead
• I don't want to have to worry about the version of Ruby or Python on the host or that ships with Sensu or whatnot
• Statically linked is a real plus for easy distribution, no library hell across distros and versions.
• I don't want to introduce a lot of memory issues with the strings coming from these text files

TODO

• Support running as a daemon with an REST GET-only interface
• Should I parse /proc/zoneinfo or anything else?