Post

ActiveRecord::ConnectionNotEstablished: Restarting Postgres for Rails

Last night I encountered this error message while building Ranting:

1
2
3
ActiveRecord::ConnectionNotEstablished (connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such file or directory
        Is the server running locally and accepting connections on that socket?
):

I vaguely remember encountering this error message a while back 🤔. I’m not certain what actually caused the error, however I figured restatrting Postgress would solve this. Here’s how to do it.

1. Look for Postgres Installation

My current setup has Postgres installed with Homebrew.

1
2
3
4
5
6
7
  $ brew list
  ==> Formulae
  ...
  cairo         liblqr          poppler
  coreutils     libnghttp2      postgresql@14
  docbook       libomp          protobuf
  ...

Seems that I have postgresql@14 installed.

2. Restart Postgres

Now, navigate to this folder:

1
  $ cd /usr/local/var

Look for the same Postgres installation folder as in Homebrew list above.

1
2
3
  $ ls
  cache		homebrew	mysql		run
  db		log		postgresql@14

cd into the Postgres folder and look for a file called postmaster.pid.

1
  $ cd postgresql@14 
1
2
3
4
5
6
7
8
  $ ls
  PG_VERSION		pg_ident.conf		pg_snapshots		pg_wal
  base			pg_logical		pg_stat			pg_xact
  global                pg_multixact            pg_stat_tmp             postgresql.auto.conf
  pg_commit_ts		pg_notify		pg_subtrans		postgresql.conf
  pg_dynshmem		pg_replslot		pg_tblspc		postmaster.opts
  pg_hba.conf		pg_serial		pg_twophase		postmaster.pid
  

Found it! Next, backup the postmaster.pid file to another folder (eg. the Desktop folder) and restart Postgres.

1
  $ mv postmaster.pid ~/Desktop
1
2
3
4
  $ brew services restart postgresql@14
  Stopping `postgresql@14`... (might take a while)
  ==> Successfully stopped `postgresql@14` (label: homebrew.mxcl.postgresql@14)
  ==> Successfully started `postgresql@14` (label: homebrew.mxcl.postgresql@14)

3. Move On with Life

Run Rails server again and that should resolve the error.

It should be safe now to delete the postmaster.pid that was backed up earlier.

This post is licensed under CC BY 4.0 by the author.