main config and rewrite script for HAproxy.

haproxy.cfg

global
  log 127.0.0.1 local2
  chroot      /var/lib/haproxy
  pidfile     /var/run/haproxy.pid
  maxconn     1000
  user        haproxy
  group       haproxy
  daemon
  stats socket /var/lib/haproxy/stats

defaults
  mode                    tcp
  log                     global
  option tcplog

listen master
  bind 127.0.0.1:3306
  mode tcp
  retries                 1
  timeout connect         10s
  timeout client          5s
  timeout server          20s
  balance roundrobin

  server node01 mysqlserver-a:3306 check port 3306

listen slave
  bind 127.0.0.1:3316
  mode tcp
  retries                 1
  timeout connect         10s
  timeout client          5s
  timeout server          20s
  balance roundrobin
  
  server node01 mysqlserver-b:3306 check port 3306
  server node01 mysqlserver-c:3306 check port 3306

haproxy.cfg.erb

global
  log 127.0.0.1 local2
  chroot      /var/lib/haproxy
  pidfile     /var/run/haproxy.pid
  maxconn     1000
  user        haproxy
  group       haproxy
  daemon
  stats socket /var/lib/haproxy/stats

defaults
  mode                    tcp
  log                     global
  option tcplog

listen master
  bind 127.0.0.1:3306
  mode tcp
  retries                 1
  timeout connect         10s
  timeout client          5s
  timeout server          20s
  balance roundrobin
  #option mysql-check user haproxy

  server node01 <%= master_node %> check port 3306

listen slave
  bind 127.0.0.1:3316
  mode tcp
  retries                 1
  timeout connect         10s
  timeout client          5s
  timeout server          20s
  balance roundrobin
  #option mysql-check user haproxy

  <%- slave_nodes.each do |slave_node| -%>
  server node01 <%= slave_node %> check port 3306
  <%- end -%>

rewrite_haproxy_config.rb

#!/usr/bin/ruby

require 'pp'
require 'erb'
require 'optparse'

LOG_FILE            = '/var/log/mha4mysql/rewrite_haproxy_config.log'
HAPROXY_CONFIG_FILE = '/etc/haproxy/haproxy.cfg'
HAPROXY_CONFIG_ERB  = '/etc/haproxy/haproxy.cfg.erb'

CLUSTER_NODES = [
  'mysqlserver-a:3306',
  'mysqlserver-b:3306',
  'mysqlserver-c:3306'
]

$args = OptionParser.new do |parser|
  parser.on('--command=VAL')
  parser.on('--ssh_user=VAL')
  parser.on('--orig_master_host=VAL')
  parser.on('--orig_master_ip=VAL')
  parser.on('--orig_master_port=VAL')
  parser.on('--new_master_host=VAL')
  parser.on('--new_master_ip=VAL')
  parser.on('--new_master_port=VAL')
  parser.on('--new_master_user=VAL')
  parser.on('--new_master_password=VAL')
end.getopts

exit unless args["command"] == 'start'

master_node = "#{args["new_master_host"]}:#{args["new_master_port"]}"
slave_nodes = CLUSTER_NODES
slave_nodes.delete("#{args["new_master_host"]}:#{args["new_master_port"]}")
slave_nodes.delete("#{args["orig_master_host"]}:#{args["orig_master_port"]}")

erb = ERB.new(File.open(HAPROXY_CONFIG_ERB).read, nil, '-')

haproxy_config = File.open(HAPROXY_CONFIG_FILE, "w")
haproxy_config.write(erb.result(binding))
haproxy_config.close

`/etc/init.d/haproxy reload`