Network partitions happen, your distributed system needs to be designed to handle them. One of the reasons they're often not tested is the difficulty in setting up failure scenarios.

I'd like to show jupsen (https://github.com/mattyw/jupsen). Jupsen is a juju plugin that allows you to model network partitions in a simple way, so you can easily test how your app handles them.

I will start by giving a brief tour of the commands available. I will then show an app writing to a mongodb replica set during a network partition. I will create a partition that causes lost writes, and demonstrate how you can guard against them.