Pagerduty's fantastic Zookeeper bug

Ok, I don’t particularly like calling a bug fantastic, in this case, it is more of a fantastic troubleshooting of a bug. What I found interesting was the layers that were unpeeled one by one to reach the probable region of the root cause. (Yeah, the root cause is probably so esoteric and confined to a specific combination of version, that it is unlikely to be looked at by anybody).