Intermittent Mysql Connection error in ROR app

Hi Everyone,

I’m getting the below error randomly in my Ruby On Rails application whenever the number of requests increases to the server.

Mysql2::Error::ConnectionError (Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)):

I’m not sure whether it is because of my server memory or is it something to do with mysql2 gem. Any help would be really appreciated, thanks in advance.

Ruby '2.5.0'
Rails '5.2.0
Mysql2 0.5.2
Phusion Passenger 5.3.4
Server version: Apache/2.4.6 (CentOS)
MySQL Community Server (GPL): 5.6.41



You can try the following:

  1. In your database.yml, increase the pool size.

  2. In database.yml, pass reconnect: true

  3. Make sure max_connections in your Mysql server configuration is a number big enough to support the pool size you are setting.



I get this error in Homebrew sometimes. I think it means it doesn’t recognize you as a local user, not sure!

This workflow for me always fixes it. Maybe it will help you figure out how to fix it using the MYSQL Community Server, they have similar issues:

$ mysql.server stop

// unset the tmp directory

$ echo $TMPDIR

$ unset TMPDIR

$ echo $TMPDIR

// validate this using echo then set it

$ echo mysqld -initialize --verbose --user=$(whoami) --basedir="$(brew --prefix mysql)" --datadir=/usr/local/var/mysql --tmpdir=/tmp

$ mysqld -initialize --verbose --user=$(whoami) --basedir="$(brew --prefix mysql)" --datadir=/usr/local/var/mysql --tmpdir=/tmp

$ mysql.server restart

$ mysql -u root -p

From there I access the mysql command line shell, set myself as root, run $flush privileges, exit mysql command line, run the login command, and error goes away

Error number 2 means file not found. This is likely a MySQL server problem.
I suggest checking system logs, MySQL logs and auth log.
This guy found the reason to be hackers trying to get in:

Hi All,

The issue gotbredolved after I increase the RAM size to 4GB from 1GB.