PSA: On macOS, upgrade to Docker v17.04+

If you’re on macOS, you’ll need to upgrade to the latest version of Docker to continue using the builder image. We’ll be enabling a turbo mode—up to a 50% speedup!*—that depends on Docker v17.04+.

Turbo mode boosts I/O performance of filesystems shared between a macOS host and the builder by sacrificing some consistency guarantees. These guarantees are largely unnecessary when compiling source code, but please be on the lookout for any builder weirdness anyway after this change lands. No need to pay attention on Linux hosts, including TeamCity, where the builder will continue to use consistent filesystem mounts.

To find out what version of Docker you’re currently running:

docker version -f {{.Client.Version}}

See the PR for details:

https://github.com/cockroachdb/cockroach/pull/16933

*Not every builder operation will observe a 50% speedup.