很显然，当DB1或DB2中的其中一台宕机之后，mmm都会立即将宕机的主机的角色全部转换到另一台DB。仔细分析Mmm的处理步骤大致是：db
一、架构模式（双master零slave）
==============================================================
一、架构模式（双master零slave）
==============================================================
---------------------[1] mmm_common.conf ——————–
主机：
功能 IP 主机名
monitor 192.168.9.159 proxy
DB db1 Server-id=1 192.168.5.157 fbfldb01
db2 Server-id=2 192.168.9.158 fbfldb02
虚拟ip：
IP0 192.168.9.154 (Write)
IP1 192.168.9.155 (Read)
IP2 192.168.9.156 (Read)
active_master_role writer
cluster_interface eth0
pid_path /var/run/mysql-mmm/mmm_agentd.pid
bin_path /usr/libexec/mysql-mmm/
replication_user slave
replication_password slave
agent_user mmm_agent
agent_password RepAgent
ip 192.168.9.157
mode master
peer db2
ip 192.168.9.158
mode master
peer db1
#
# ip 192.168.100.51
# mode slave
#
hosts db1, db2 #能够作为writer的host
ips 192.168.100.250 #writer的虚拟IP，应用的写请求直接访问这里的ip即可
mode exclusive #只有两种模式：exclusive是排他，在这种模式下任何时候只能一个host拥有该角色，balanced模式下可以多个host同时拥有此角色。一般writer是ex，reader是ba
hosts db1, db2 #能够作为reader的host
ips 192.168.100.251, 192.168.100.252 #reader的虚拟IP，应用的读请求直接访问这里的ip即可
mode balanced
--------------------[2] mmm_mon.conf ———————–
include mmm_common.conf
ip 127.0.0.1
pid_path /var/run/mmm_mond.pid
bin_path /usr/lib/mysql-mmm/
status_path /var/lib/misc/mmm_mond.status
ping_ips 192.168.9.157, 192.168.9.158,192.168.9.254
monitor_user mmm_monitor
monitor_password RepMonitor
debug 0
------------------------[4] mmm_agent.conf ——————–
include mmm_common.conf
this db1 #在DB1上就写成这样，DB2上就写成this db2，写错了，将有一台DB的mysql-mmm-agent开不起来！切记！
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