MHA部署及配置是否OK，我们可以借助于MHA自带的masterha_check_ssh以及masterha_check_repl脚本来检测。masterha_check_repl检测是保证MHA成功切换的重要一步。本文主要描述了masterha_check_repl这个检测脚本到底做了些什么事情。有助于更好的理解MHA的相关原理及过程等。

1、当前的主从环境
[root@vdbsrv1 ~]# more /etc/hosts
127.0.0.1 localhost.localdomain localhost
192.168.1.6 vdbsrv1 #master
192.168.1.7 vdbsrv2 #slave1
192.168.1.8 vdbsrv3 #slave2
192.168.1.12 vdbsrv4 #manager

###os环境
[root@vdbsrv4 ~]# more /etc/issue
CentOS release 5.9 (Final)
Kernel \r on an \m

###mysql环境
[root@vdbsrv4 ~]# mysql -e "show variables like 'version'"
+---------------+------------+
| Variable_name | Value |
+---------------+------------+
| version | 5.6.22-log |
+---------------+------------+

[root@vdbsrv4 ~]# masterha_manager --version
masterha_manager version 0.56.

2、当前的MHA配置信息
[root@vdbsrv4 ~]$ more /etc/masterha/app1.cnf
[server default]
manager_workdir=/var/log/masterha/app1
manager_log=/var/log/masterha/app1/manager.log

user=mha
password=xxx
ssh_user=root
repl_user=repl
repl_password=repl
ping_interval=1
shutdown_script=""
master_ip_online_change_script=""
report_script=""
master_ip_failover_script=/tmp/master_ip_failover

[server1]
hostname=vdbsrv1
master_binlog_dir=/data/mysqldata

[server2]
hostname=vdbsrv2
master_binlog_dir=/data/mysqldata

[server3]
hostname=vdbsrv3
master_binlog_dir=/data/mysqldata/
#candidate_master=1

3、masterha_check_repl检测步骤
a、读取配置文件
b、检测配置文件中列出的mysql服务器(识别主从)
c、检测从库配置信息
read_only参数
relay_log_purge参数
复制过滤规则
d、ssh等效性验证
e、检测主库保存binlog脚本(save_binary_logs) ，主要是用于在master死掉后从binlog读取日志
f、检测各从库能否apply差量binlog(apply_diff_relay_logs)
g、检测IP切换，如果有部署脚本

4、实际检测过程
[root@vdbsrv4 ~]# masterha_check_repl --conf=/etc/masterha/app1.cnf
Fri Apr 17 18:48:41 2015 - [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping.
Fri Apr 17 18:48:41 2015 - [info] Reading application default configuration from /etc/masterha/app1.cnf..
Fri Apr 17 18:48:41 2015 - [info] Reading server configuration from /etc/masterha/app1.cnf.. ###读取配置文件
Fri Apr 17 18:48:41 2015 - [info] MHA::MasterMonitor version 0.56.
Fri Apr 17 18:48:42 2015 - [info] GTID failover mode = 0
Fri Apr 17 18:48:42 2015 - [info] Dead Servers: ###开始检测配置文件中列出的mysql服务器(识别主从)
Fri Apr 17 18:48:42 2015 - [info] Alive Servers:
Fri Apr 17 18:48:42 2015 - [info] vdbsrv1(192.168.1.6:3306)
Fri Apr 17 18:48:42 2015 - [info] vdbsrv2(192.168.1.7:3306)
Fri Apr 17 18:48:42 2015 - [info] vdbsrv3(192.168.1.8:3306)
Fri Apr 17 18:48:42 2015 - [info] Alive Slaves:
Fri Apr 17 18:48:42 2015 - [info] vdbsrv2(192.168.1.7:3306) Version=5.6.22-log (oldest major version between slaves) log-bin:enabled
Fri Apr 17 18:48:42 2015 - [info] Replicating from 192.168.1.6(192.168.1.6:3306)
Fri Apr 17 18:48:42 2015 - [info] vdbsrv3(192.168.1.8:3306) Version=5.6.22-log (oldest major version between slaves) log-bin:enabled
Fri Apr 17 18:48:42 2015 - [info] Replicating from 192.168.1.6(192.168.1.6:3306)
Fri Apr 17 18:48:42 2015 - [info] Current Alive Master: vdbsrv1(192.168.1.6:3306)
Fri Apr 17 18:48:42 2015 - [info] Checking slave configurations.. ###检测从库配置信息
Fri Apr 17 18:48:42 2015 - [info] read_only=1 is not set on slave vdbsrv2(192.168.1.7:3306).
Fri Apr 17 18:48:42 2015 - [warning] relay_log_purge=0 is not set on slave vdbsrv2(192.168.1.7:3306).
Fri Apr 17 18:48:42 2015 - [info] read_only=1 is not set on slave vdbsrv3(192.168.1.8:3306).
Fri Apr 17 18:48:42 2015 - [warning] relay_log_purge=0 is not set on slave vdbsrv3(192.168.1.8:3306).
Fri Apr 17 18:48:42 2015 - [info] Checking replication filtering settings.. ###检测复制过滤规则
Fri Apr 17 18:48:42 2015 - [info] binlog_do_db= , binlog_ignore_db=
Fri Apr 17 18:48:42 2015 - [info] Replication filtering check ok.
Fri Apr 17 18:48:42 2015 - [info] GTID (with auto-pos) is not supported
Fri Apr 17 18:48:42 2015 - [info] Starting SSH connection tests.. ###ssh等效性验证
Fri Apr 17 18:48:43 2015 - [info] All SSH connection tests passed successfully.
Fri Apr 17 18:48:43 2015 - [info] Checking MHA Node version..
Fri Apr 17 18:48:44 2015 - [info] Version check ok.
Fri Apr 17 18:48:44 2015 - [info] Checking SSH publickey authentication settings on the current master..
Fri Apr 17 18:48:44 2015 - [info] HealthCheck: SSH to vdbsrv1 is reachable.
Fri Apr 17 18:48:44 2015 - [info] Master MHA Node version is 0.56.
Fri Apr 17 18:48:44 2015 - [info] Checking recovery script configurations on vdbsrv1(192.168.1.6:3306)..###检测主库保存binlog脚本
Fri Apr 17 18:48:44 2015 - [info] Executing command: save_binary_logs --command=test --start_pos=4 --binlog_dir=/data/mysqldata
--output_file=/var/tmp/save_binary_logs_test --manager_version=0.56 --start_file=mysql-bin.000012
Fri Apr 17 18:48:44 2015 - [info] Connecting to root@192.168.1.6(vdbsrv1:22)..
Creating /var/tmp if not exists.. ok.
Checking output directory is accessible or not..
ok.
Binlog found at /data/mysqldata, up to mysql-bin.000012
Fri Apr 17 18:48:44 2015 - [info] Binlog setting check done. ###以下部分检测各从库能否apply差量binlog
Fri Apr 17 18:48:44 2015 - [info] Checking SSH publickey authentication and checking recovery script configurations on all alive slave servers..
Fri Apr 17 18:48:44 2015 - [info] Executing command : apply_diff_relay_logs --command=test --slave_user='mha' --slave_host=vdbsrv2
--slave_ip=192.168.1.7 --slave_port=3306 --workdir=/var/tmp --target_version=5.6.22-log --manager_version=0.56
--relay_log_info=/data/mysqldata/relay-log.info --relay_dir=/data/mysqldata/ --slave_pass=xxx
Fri Apr 17 18:48:44 2015 - [info] Connecting to root@192.168.1.7(vdbsrv2:22)..
Checking slave recovery environment settings..
Opening /data/mysqldata/relay-log.info ... ok.
Relay log found at /data/mysqldata, up to vdbsrv2-relay-bin.000006
Temporary relay log file is /data/mysqldata/vdbsrv2-relay-bin.000006
Testing mysql connection and privileges.. done. #Author : Leshami
Testing mysqlbinlog output.. done. #Blog : http://blog.csdn.net/leshami
Cleaning up test file(s).. done.
Fri Apr 17 18:48:44 2015 - [info] Executing command : apply_diff_relay_logs --command=test --slave_user='mha' --slave_host=vdbsrv3
--slave_ip=192.168.1.8 --slave_port=3306 --workdir=/var/tmp --target_version=5.6.22-log --manager_version=0.56
--relay_log_info=/data/mysqldata/relay-log.info --relay_dir=/data/mysqldata/ --slave_pass=xxx
Fri Apr 17 18:48:44 2015 - [info] Connecting to root@192.168.1.8(vdbsrv3:22)..
Checking slave recovery environment settings..
Opening /data/mysqldata/relay-log.info ... ok.
Relay log found at /data/mysqldata, up to vdbsrv3-relay-bin.000006
Temporary relay log file is /data/mysqldata/vdbsrv3-relay-bin.000006
Testing mysql connection and privileges.. done.
Testing mysqlbinlog output.. done.
Cleaning up test file(s).. done.
Fri Apr 17 18:48:45 2015 - [info] Slaves settings check done.
Fri Apr 17 18:48:45 2015 - [info]
vdbsrv1(192.168.1.6:3306) (current master)
+--vdbsrv2(192.168.1.7:3306)
+--vdbsrv3(192.168.1.8:3306)

Fri Apr 17 18:48:45 2015 - [info] Checking replication health on vdbsrv2..
Fri Apr 17 18:48:45 2015 - [info] ok.
Fri Apr 17 18:48:45 2015 - [info] Checking replication health on vdbsrv3..
Fri Apr 17 18:48:45 2015 - [info] ok.
Fri Apr 17 18:48:45 2015 - [info] Checking master_ip_failover_script status: ###检测IP切换
Fri Apr 17 18:48:45 2015 - [info] /tmp/master_ip_failover --command=status --ssh_user=root --orig_master_host=vdbsrv1
--orig_master_ip=192.168.1.6 --orig_master_port=3306

IN SCRIPT TEST====/sbin/ifconfig eth0:0 down==/sbin/ifconfig eth0:0 192.168.1.13/24===

Checking the Status of the script.. OK
Fri Apr 17 18:48:45 2015 - [info] OK.
Fri Apr 17 18:48:45 2015 - [warning] shutdown_script is not defined.
Fri Apr 17 18:48:45 2015 - [info] Got exit code 0 (Not master dead).

MySQL Replication Health is OK.