I’ve been pulling my hair out for the last couple days over this one.
It turns out that the Ruby client library throws a segfault (using Ruby 2.2.3 & 2.3.1) when port 8093 is not available. I’m running couchbase in a Docker container, and only exposed the secure port (18093).
I can’t log a bug report on your JIRA because you need an account and users can’t sign up freely. This is IMHO terrible for open-source because developers can’t quickly & easily submit bug reports without an admin’s blessing.