drydock is a phabricator prototype application which is designed for allicating and caching resources like VMs, Working Copies, etc and then handing them to harbormaster for executing test jobs.

The upstream phabricator project has been actively developing drydock in recent weeks, for example see changelog/2015.41 and the linked tracking tasks.

Summary: Upstream is self-hosting phabricator builds in harbormaster and building working copies in drydock. It supports multiple trust-groups for isolation and you can assign VM instances to any arbitrary group, then assign tests to a group and they will be executed on the VM instances from the corresponding trust group. The upstream description is probably better than my summary so I encourage you to read more about it there.

This task is just here to remind & encourage us to evaluate these tools and apply them to our own CI needs as much as possible since that will lead to much more integrated infrastructure and hopefully reduced fragmentation of our tooling/expertise.