activerecord-mysql-reconnect

It is the library to reconnect automatically when ActiveRecord is disconnected from MySQL.

Gem Version Build Status

Installation

Add this line to your application's Gemfile:

gem 'activerecord-mysql-reconnect'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activerecord-mysql-reconnect

Usage

require 'activerecord/mysql/reconnect'
require 'logger'

ActiveRecord::Base.establish_connection(
  adapter:  'mysql2',
  host:     '127.0.0.1',
  username: 'root',
  database: 'employees',
)

ActiveRecord::Base.logger = Logger.new($stdout)
ActiveRecord::Base.logger.formatter = proc {|_, _, _, message| "#{message}\n" }
ActiveRecord::Base.enable_retry = true
ActiveRecord::Base.execution_tries = 3

class Employee < ActiveRecord::Base; end

p Employee.count
system('sudo /etc/init.d/mysqld restart')
p Employee.count

shell> ruby test.rb
   (64.1ms)  SELECT COUNT(*) FROM `employees`
300024
Stopping mysqld:                                           [  OK  ]
Starting mysqld:                                           [  OK  ]
   (0.4ms)  SELECT COUNT(*) FROM `employees`
Mysql2::Error: MySQL server has gone away: SELECT COUNT(*) FROM `employees`
MySQL server has gone away. Trying to reconnect in 0.5 seconds.
   (101.5ms)  SELECT COUNT(*) FROM `employees`
300024

without_retry

ActiveRecord::Base.without_retry do
  Employee.count
end

retryable_transaction

ActiveRecord::Base.retryable_transaction do
  Employee.create(emp_no: 1, birth_date: Time.now, first_name: 'Scott', last_name: 'Tiger', hire_date: Time.now)
  Employee.create(emp_no: 2, birth_date: Time.now, first_name: 'Scott', last_name: 'Tiger', hire_date: Time.now)
  Employee.create(emp_no: 3, birth_date: Time.now, first_name: 'Scott', last_name: 'Tiger', hire_date: Time.now)
end

Use on rails

Gemfile

gem 'activerecord-mysql-reconnect'

environment file

MyApp::Application.configure do
  ...
  config.active_record.enable_retry = true
  config.active_record.execution_tries = 10 # times
  config.active_record.execution_retry_wait = 1.5 # sec
  config.active_record.retry_mode = :rw # default: `:r`, valid values: `:r`, `:rw`, `:force`
  ...
ene

Retry mode

  • :r Retry only SELECT / SHOW / SET
  • :rw Retry in all SQL, but does not retry if Lost connection has happened in write SQL
  • :force Retry in all SQL

Running tests on local

mysql.server start
export ACTIVERECORD_MYSQL_RECONNECT_MYSQL_START='mysql.server start'
export ACTIVERECORD_MYSQL_RECONNECT_MYSQL_STOP='mysql.server stop'
export ACTIVERECORD_MYSQL_RECONNECT_MYSQL_RESTART='killall -9 mysqld; sleep 3; mysql.server restart; true'
bundle install
bundle exec rake