postgresql - Postgres just randomly stopped working (Rails, PGSQL.5432)

Question

I've been using the same Postgres database in this same app for a month with no problems, and I didn't change anything in the database before this error randomly came up today. However, today Postgres randomly started throwing this error when I try to "rails s" (I get the same type of error when running createdb or createuser):

Exiting /Users/Joe/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.2/lib/active_record/connection_adapters/postgresql_adapter.rb:1194: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 "/tmp/.s.PGSQL.5432"?

What's really weird is that my friend had the exact same errors yesterday (working on the same app), and it was fixed by him running the script from http://nextmarvel.net/blog/2011/09/brew-install-postgresql-on-os-x-lion/. After running the script, he uninstalled and reinstalled the PG gem to make everything work. However, he is running OS X Lion, and I am running Snow Leopard, so that script wouldn't work for me.

Any ideas of (1) why this would randomly start happening and (2) how to fix it?

Answer 1

I had a similar problem today, although in my case postgres (installed via homebrew on MacOS 10.8) wasn't running but I couldn't start or restart it. It appeared that due to a crash a zombie was blocking the socket, to resolve it i did the following

lsof -i :5432

this showed the PID of the process blocking, I simply killed it with

kill -9 PID

and postgres restarted fine.

HTH