Question

I am new to Ruby/Rails and PostgreSQL. Is it possible to have to multiple rails apps access a psql local database at the same, if not how do you switch between applications?
Currently RailsApp1 is interacting with my psql db as expected, however RailsApp2 cannot connect and rake commands abort.

Running on: OSX Mountain Lion, ruby 1.9.3p194, rails 3.2.8, psql 9.2.1.

~/RailsApp2 #: rake db:migrate
rake aborted!
could not connect to server: No such file or directory
    Is the server running locally and accepting
    connections on Unix domain socket "/var/pgsql_socket/.s.PGSQL.5432"?

Tasks: TOP => db:migrate
(See full trace by running task with --trace)

Thank you in advance for the help.

Answer 1

PostgreSQL uses a client-server model, so the fact is you just connect to the server and multiple applications can make it work. Your specific problem sounds like the server isn’t running or isn’t accepting connections. Steps to try in order:

1. ps -A | grep post looking for postgres or postmaster processes. If not found start the server using the pg_ctl program.
2. Assuming it is running try setting the PGHOST environment variable to “localhost” so that it forces rake, psql, etc. to connect over TCP/IP. This would help if the UNIX socket is missing or just not where the client apps expect it to be.
3. If those two fail, find your postgresql logs (sometimes called serverlog, and sometimes in a pg_log directory) and post error messages.