Intro
I began to implement the autmoation of speedtest checks. I was running the jobs every 10 minutes, but we noticed something flaky in the results. On the hour and on the half hour the tests seemed to be garbage. What’s going on?
Our findings
Well, if you use a scheduler to run a speedtest every 10 minutes, it will start exactly on the hour and exactly on the half-hour, amongst other start times. We were running it eight times to test eight different paths. Only the last two were returning reliable results. The early ones were throwing errors. So I introduced an offset to run the jobs at 2,12,22,32,42,52 minutes. And with this offset, the results became much more reliable.
The inevitable conclusion is that too many other people are running tests exactly on the hour and half hour. A single run takes roughly 30 seconds to complete. And it must be that the servers which speedtest rely on are simply overwhelmed and refuse to do more tests.
References and related
There is a linux script written in python that implements the full speedtest. https://pypi.org/project/speedtest-cli/ It really works, which is cool.
But as well there is a RPM package you can get from the speedtest site itself.
nperf.com looks like a better test than speedtest. I’m going to see if it can be scripted.