Postgresql adapter (pg): could not connect to server

Question

I get this error every this I run my Rails app (It cannot connect to my local Postgresql)

/Users/leonardo/.rvm/gems/ruby-1.9.3-p362/gems/activerecord-3.2.11/lib/
active_record/connection_adapters/postgresql_adapter.rb:1208: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"?

I'm using Postgres.app that it's correctly running.

If I run

$ psql

I can login properly to Postgresql console.

$ which psql
 /Applications/Postgres.app/Contents/MacOS/bin/psql

Gemfile

source 'https://rubygems.org'
ruby "1.9.3"

gem 'rails', '3.2.11'
gem "pg"

database.yml

development:
  adapter: postgresql
  encoding: unicode
  username: leonardo
  password: 
  database: zapping
  port: 5432  

Postgresql (Console)

$ psql
leonardo=# \l

Solution 1

Try adding host: localhost to your database.yml. (Based on: https://stackoverflow.com/a/10793186/919641)

Solution 2

Your Pg gem was compiled against the PostgreSQL libpq pre-installed in Mac OS X and you're using the psql that you installed in a newer version, or vice versa.

This can be worked around by specifying a TCP/IP connection, by adding localhost to database.yml, but it's better to compile the Pg gem against the libpq for the server you're actually running. To do that, you should be able to set the PATH environment variable to the folder with the correct pg_config in it before compiling. In your case that'll be somewhere within Postgres.app.

Solution 3

If it does not work even after adding host: localhost, remove the postmaster.pid

rm /usr/local/var/postgres/postmaster.pid

Solution 4

you should add host: localhost to your db config...

Solution 5

Since This was the first post that appeared in my search result, I have decided to post the updated fix for this. Since none of the above suggestion worked for me.

brew postgresql-upgrade-database

It upgraded postgresql data and moved my old version. I was on 9.6 instead of 10.4

Found the solution here

View more solutions

Comments

[Rizon]

Craig, can you please elaborate this one? Where and which env. variable should I set exactly?

[wik]

re-installation of the pg gem were also required

[haslo]

Thanks, this answer helped me fix it. The steps I took were simple: 1) gem uninstall pg, 2) bundle install, done.

[rwheadon]

This solution, ultimately in my case, would have fixed my issue with Rails not being able to start. I went a little different approach on the way to realizing this. I actually created a symlink as described in This Post

[BvuRVKyUVlViVIc7]

Im not sure why i get downvoted, I answered 5 minutes before! the accepted answer (which has the same solution like my post)?

[Jason Kim]

Thanks. In my case, I had to add host: db.

[Mike Vallano]

This solved the problem that I had. Even though running brew services start postgresql said it was successful, running ps x | grep postgres showed no server running. I followed the steps here (which include removing the postmaster.pid) and it solved the problem for me: coderwall.com/p/zf-fww/…

[Joshua F. Rountree]

This works if your computer crashes and you do a forced shutdown but postgres wasn't properly terminated, sometimes the pid file will get stuck there... removing it helps get it going again.

[SexxLuthor]

Perfect answer, and although updating database.yml works too, I think this is probably the best and most correct solution for this problem. If you've, say, installed Postgresql via Homebrew after installing pg, you might see this error. Then follow @haslo's instructions above.

[Craig Ringer]

No no no do NOT do this! It's only OK if you verify that no postgres processes are still running. It should rarely if ever be necessary; it can only arise if some other process happens to get assigned the pid the postmaster had.

[Pradyumna Shembekar]

Should be okay for local postgres connections.

[Christoph]

This fixed it for me. I had uninstalled/reinstall postgres and the gem needed to be rebuilt.

[David Greco]

This was my problem, I don't understand the reply above from @CraigRinger what is the harm in this? It was immediately rebuilt for me by the service when it finally started.

[Craig Ringer]

@DavidGreco postmaster.pid serves as an interlock that stops one postgres from starting while another is still writing to the database file. If you remove it, you might have two (or more) postgres processes writing to the same database without coordinating with each other, resulting in massive database corruption. So do not do it unless you have made absolutely sure no other postgres processes are surviving and accessing the same data directory.