How to setup MMM control under CentOS 6.1

Jephe Wu - http://linuxtechres.blogspot.com

Environment: CentOs 6.1, MMM 2.2.1, MySQL 5.1.52
Objective: setup MMM among the databases to gain HA and load balance for read access

Steps:

1. install required packages for mmm agent on database servers
yum -y install perl-Config-IniFiles
yum -y install mysql-mmm mysql-mmm-agent mysql-mmm-tools mysql-proxy

2. install required packages for mmm monitor on monitoring host
yum -y install mysql-mmm-monitor

chkconfig mysql-mmm-agent on
chkconfig mysql-mmm-monitor on

3. preparing ips for databases
db1: 172.17.7.1 master
db2: 172.17.7.2 master
db3: 172.17.7.3 slave

master exclusive ip: 172.17.7.4
slave balanced ip addresses: 172.17.7.5, 172.17.7.6, 172.17.7.7

4. setup /etc/mysql-mmm/mmm_agent.conf to change 'this' line to db1/db2 or db3
5. setup /etc/mysql-mmm/mmm_common.conf for all monitor and agents

# more /etc/mysql-mmm/mmm_common.conf
active_master_role          writer

<host default>
    cluster_interface       bond0

    pid_path                /var/run/mysql-mmm/mmm_agentd.pid
    bin_path                /usr/libexec/mysql-mmm/

    replication_user        replication
    replication_password    replication_password

    agent_user              mmm_agent
    agent_password          agent_password
</host>

<host db1>
    ip                      172.17.7.1
    mode                    master
    peer                    db2
</host>

<host db2>
    ip                      172.17.7.2
    mode                    master
    peer                    db1
</host>

<host db3>
    ip                      172.17.7.3
    mode                    slave
</host>

<role writer>
    hosts                   db1, db2
    ips                     172.17.7.4
    mode                    exclusive
</role>

<role reader>
    hosts                   db1, db2, db3
    ips                     172.17.7.5, 172.17.7.6, 172.17.7.7
    mode                    balanced
</role>

6. start up agents on database servers first
on db1,db2 then db3, to start up mmm agent: /etc/init.d/mysql-mmm-agent start

7. start up monitor process on monitoring host
on mon01, to start up: /etc/init.d/mysql-mmm-monitor start

8. bring up them online from mon01
mon01# mmm_control set_online db1
mon01# mmm_control set_online db2
mon01# mmm_control set_online db3

root@mon01:/etc/mysql-proxy/ # mmm_control show
  db1(172.17.7.1) slave/REPLICATION_DELAY. Roles:
  db2(172.17.7.2) master/ONLINE. Roles: reader(172.17.7.5), reader(172.17.7.6)
  db3(172.17.7.3) master/ONLINE. Roles: reader(172.17.7.7), writer(172.17.7.4)

9. FAQ
a.   read_only (on/off) from show variables comand in mysql
if db2 and db3 are writer, when writer role goes to db3, mmm will set read_only flag for db2 to prevent any writing process, but only for normal user, not root.