Currently flog (as do the other metrics) run even when the build fails. Given that flog is generally pretty slow to run (in my case 2-3 times slower than the build itself), it would seem this is not the optimal setup.

I would recommend NOT processing any of the metric post actions unless the build succeeds. Alternately, config parameters could be setup to specify whether the action runs only on success or not (in case there are some cases to always run them).