Debugging Races

Triggering races

Someone pointed me to the stress test script on this wiki. While it was immeasurably helpful, I have found a few more things that help me reproduce and instrument races. The previous link also includes an updated script which adds a counter and timing to the output. I find it useful to know how long it took to trigger a race, or how long it was stressed without triggering.

I also install stress to create contention on cpus, ram, io, etc.
E.g. stress --cpu 8 --io 4 --vm 2 -d 2 --timeout 60m. I imagine this would be nice to randomize in the script(s) linked in the first paragraph.

AWS

I find that running on a small or medium instance on AWS helps to trigger races more quickly than my local hardware. Particularly useful are instances that shares CPU time -- t.n instances currently. If you locally build the test to stress you may still need to rsync over the build environment as some tests look for files in the build tree. You'll also need to install mongo.

TODO: more details on stressing on AWS.

• sudo apt-get install juju-mongodb