Thomas Mayfield bio photo

Thomas Mayfield

Polyglot programmer who loves the weird beautiful chaos of humans building software together. Fitness nerd. Southern kid living in Massachusetts.

Postgres connection errors after upgrading Ruby

After I recently upgraded Ruby 2.0.0 from p195 to p247, I started getting this error when starting some of my Rails projects for development:

/Users/tmayfield/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/connection_adapters/postgresql_adapter.rb:825:in `initialize': could not connect to server: No such file or directory (PG::Error)
Is the server running locally and accepting connections on Unix domain socket "/var/pgsql_socket/.s.PGSQL.5432"?

The solution, as it turned out, was pretty simple: the config/database.yml file in the affected project was missing an explict entry for the database hostname. Adding host: localhost to the test and development entries got things rolling again.

A shiny nickle to anyone who can tell me what changed between minor patchlevels of Ruby to cause this (or perhaps, why it worked before without an explict host setting).