Socket File "/var/pgsql_socket/.s.PGSQL.5432" Missing In Mountain Lion (OS X Server)

I just upgraded my MacMini Server from Lion Server to Mountain Lion using OS X Server. I am having the same problem with PostgreSQL that I did last year when I first installed Lion Server.

When I try to do any kind of PostgreSQL terminal command I get the following notorious error message that many have gotten over the years:

psql: 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"?

I was attempting to change the password for _postgres when I got the error. I tried several commands but got the same error. I just rebooted my server but no luck. I logged in as root to look at /var/pgsql_socket and the folder is empty. Folder /var/pgsql_socket_alt is also empty.

I have checked online about this. However just about all of the solutions I have read, including on Stack Overflow, suggest a removal and reinstall of PostgreSQL. I do not know but this does not seem like a plausible option because several options on the Server App use PostgreSQL. I contacted Apple Enterprise Support (no agreement) and I was told that my issue would have to be solved by the developers which would cost $695.

I have a website that is down right now because I cannot rebuild it. I don't know where to turn for help with this at this point. I will continue looking online to see if I can find something. However I hope that someone can give me an answer quick so I can rebuild my database.

Update: 12/13/2012 15:33 GMT-6

Here is my output for ps auwx|grep postg:

_postgres      28123   0.0  0.1  2479696   7724   ??  Ss    3:01PM   0:00.04 /Applications/Server.app/Contents/ServerRoot/usr/bin/postgres_real -D /Library/Server/PostgreSQL For Server Services/Data -c listen_addresses= -c log_connections=on -c log_directory=/Library/Logs/PostgreSQL -c log_filename=PostgreSQL_Server_Services.log -c log_line_prefix=%t  -c log_lock_waits=on -c log_statement=ddl -c logging_collector=on -c unix_socket_directory=/Library/Server/PostgreSQL For Server Services/Socket -c unix_socket_group=_postgres -c unix_socket_permissions=0770
server1        28216   0.0  0.0  2432768    620 s000  R+    3:02PM   0:00.00 grep postg
_postgres      28138   0.0  0.0  2439388    752   ??  Ss    3:01PM   0:00.01 postgres: stats collector process                           
_postgres      28137   0.0  0.0  2479828   1968   ??  Ss    3:01PM   0:00.00 postgres: autovacuum launcher process                           
_postgres      28136   0.0  0.0  2479696    544   ??  Ss    3:01PM   0:00.00 postgres: wal writer process                           
_postgres      28135   0.0  0.0  2479696    732   ??  Ss    3:01PM   0:00.01 postgres: writer process                           
_postgres      28134   0.0  0.0  2479696    592   ??  Ss    3:01PM   0:00.00 postgres: checkpointer process                           
_postgres      28131   0.0  0.0  2439388    368   ??  Ss    3:01PM   0:00.00 postgres: logger process 

Update: 12/13/2012 18:10 GMT-6

After intense web searching this video was found. I was able to get PostgreSQL working and remove the error. I am able to connect using pgadmin and phppgadmin. I was about to go back to Lion Server because of sheer frustration. Now I will not have to.

http://www.youtube.com/watch?v=y1c7WFMMkZ4

I was able to add the following to my .bash_profile to prevent the error:

export PGHOST=localhost

This works because:

If you omit the host name, psql will connect via a Unix-domain socket to a server on the local host, or via TCP/IP to localhost on machines that don't have Unix-domain sockets.

Your OS supports Unix domain sockets, but PostgreSQL's Unix socket that psql needs either doesn't exist or is in a different location than it expects.

Specifying a hostname explicitly as localhost forces psql to use TCP/IP. Setting an environment variable PGHOST is one of the ways to achieve that. It's documented in psql's manual.

Try paste in console this:

$ mkdir /var/pgsql_socket/ 

$ ln -s /private/tmp/.s.PGSQL.5432 /var/pgsql_socket/

I was able to solve by simply filling in 127.0.0.1 for the PostgreSQL host address rather than leaving it blank. (Django Example)

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'database_name',
        'USER': 'database_user',
        'PASSWORD': 'pass',
        'HOST': '127.0.0.1',
        'PORT': '',
        }
}

Open 'postgresql.conf' in you favourite editor. Look for the variable 'unix_socket_directories', it will most likely look like this:

unix_socket_directories = '/private/tmp/'

Change the line to this:

unix_socket_directories = '/var/pgsql_socket/'

Note if you want the socket files in more than one directory comma separate them.

A much more simple solution (thanks to http://daniel.fone.net.nz/blog/2014/12/01/fixing-connection-errors-after-upgrading-postgres/) . I had upgraded to postgres 9.4. In my case, all I needed to do (after a day of googling and not succeeding)

gem uninstall pg
gem uninstall activerecord-postgresql-adapter
bundle install

Restart webrick, and done!