Mesos is a superset of Yarn and also a bit lower level. In fact, there is a project that allows you to run Yarn on top of mesos thereby getting the best of both worlds. Kind of by design, you couldn't really run mesos on top of Yarn.

http://www.apache-myriad.org

I use Mesos in production and it is great stuff. It also helps knowing 100% of the backend of Siri, 100% of Twitter, much of eBay, PayPal, Airbnb, Uber, etc all run entirely on mesos. It is simply battle tested.