database.yml

development:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: mysql_read_timeout_development
  pool: 5
  username: root
  password:
  socket: /tmp/mysql.sock
  read_timeout: 1

without_timeout:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: mysql_read_timeout_development
  pool: 5
  username: root
  password:
  socket: /tmp/mysql.sock

employee.rb

class Employee < ActiveRecord::Base
  def self.sleep
    find_by_sql 'select sleep(2) as name'
  end
end

employees_contoller.rb

class EmployeesController < ApplicationController
  def show
    begin
      Employee.sleep
    rescue ActiveRecord::StatementInvalid
      ActiveRecord::Base.establish_connection('without_timeout')
      Employee.sleep
    end
    @employee = Employee.find(params[:id])
    
    respond_to do |format|
      format.html # show.html.erb
      format.json { render :json => @employee }
    end
  end
end