集群信息
角色 IP地址 ServerID 类型
Master 192.168.244.10 1 写入
Candicate master 192.168.244.20 2 读
Slave 192.168.244.30 3 读
Monitor host 192.168.244.40 监控集群组
MHA具体的搭建步骤和原理，可参考另外一篇文章：
MySQL高可用方案MHA的部署和原理 http://www.linuxidc.com/Linux/2017-05/144086.htm
为了通过MHA的日志清晰判断MHA自动Failover的实现原理，需模拟如下场景：
当主库发生故障时，master中还有一部分binlog日志没有传输到Candicate master和Slave上，且Slave上的二进制日志多于Candicate master上。
尝试了几种方案，总算如愿以偿。
方案一：
1. 关闭Candicate master和Slave的主从复制。
2. 通过存储过程生成测试数据
3. 开启Candicate master和Slave的主从复制并kill掉master的mysqld进程，模拟主库发生故障，进行自动failover操作
为此，还特意写了个脚本，可惜的是，效果并不理想，在自动Failover的过程中，显示MHA Manager到master的“SSH is NOT reachable”。
方案二：
通过tc命令对Candicate master和Slave的网卡分别设置不同的传输速率，确保发送到Candicate master的日志量小于Slave上的。
很可惜，效果同方案一一样。
方案三：
在主从复制中，直接关闭master的mysqld数据库。
但是，通过这样方式，并不会实现Slave上的二进制日志多于Candicate master的效果。
方案四：
通过截取relay log，在关掉slave的情况下，修改master.info和relay-log.info的位置点来人为制造Candicate master的日志量小于Slave的。
事后想想，其实这样的方法就等同于先关闭Candicate master的主从复制，再在master上执行一段操作，再关闭slave上的主从复制，再在master上执行一段操作。
这样不就实现了master的binlog > slave 的relay log >Candicate master的relay log。
方案四总算如愿以偿
下面通过方案四看看MHA的实现原理
mysql> create table sbtest.b(id int,name varchar(10)); Query OK,0 rows affected (0.12 sec)
mysql> insert into sbtest.b values(1,’a’);
Query OK,1 row affected (0.00 sec)
mysql> insert into sbtest.b values(2,’b’);
Query OK,1 row affected (0.01 sec)
mysql> insert into sbtest.b values(3,’c’);
Query OK,1 row affected (0.00 sec)
mysql> insert into sbtest.b values(4,’d’);
Query OK,1 row affected (0.00 sec)
mysql> insert into sbtest.b values(5,’e’);
Query OK,1 row affected (0.01 sec)
Master
mysql> show binlog events; +------------------+------+-------------+-----------+-------------+------------------------------------------------+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | +------------------+------+-------------+-----------+-------------+------------------------------------------------+ | mysql-bin.000001 | 4 | Format_desc | 1 | 120 | Server ver: 5.6.31-log, Binlog ver: 4 | | mysql-bin.000001 | 120 | Query | 1 | 238 | create table sbtest.b(id int,name varchar(10)) | | mysql-bin.000001 | 238 | Query | 1 | 315 | BEGIN | | mysql-bin.000001 | 315 | Query | 1 | 421 | insert into sbtest.b values(1,'a') | | mysql-bin.000001 | 421 | Xid | 1 | 452 | COMMIT /* xid=102 */ | | mysql-bin.000001 | 452 | Query | 1 | 529 | BEGIN | | mysql-bin.000001 | 529 | Query | 1 | 635 | insert into sbtest.b values(2,'b') | | mysql-bin.000001 | 635 | Xid | 1 | 666 | COMMIT /* xid=103 */ | | mysql-bin.000001 | 666 | Query | 1 | 743 | BEGIN | | mysql-bin.000001 | 743 | Query | 1 | 849 | insert into sbtest.b values(3,'c') | | mysql-bin.000001 | 849 | Xid | 1 | 880 | COMMIT /* xid=104 */ | | mysql-bin.000001 | 880 | Query | 1 | 957 | BEGIN | | mysql-bin.000001 | 957 | Query | 1 | 1063 | insert into sbtest.b values(4,'d') | | mysql-bin.000001 | 1063 | Xid | 1 | 1094 | COMMIT /* xid=105 */ | | mysql-bin.000001 | 1094 | Query | 1 | 1171 | BEGIN | | mysql-bin.000001 | 1171 | Query | 1 | 1277 | insert into sbtest.b values(5,'e') | | mysql-bin.000001 | 1277 | Xid | 1 | 1308 | COMMIT /* xid=106 */ | +------------------+------+-------------+-----------+-------------+------------------------------------------------+ 17 rows in set (0.01 sec)
Slave
mysql> show relaylog events in 'mysqld-relay-bin.000002'; +-------------------------+------+-------------+-----------+-------------+------------------------------------------------+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | +-------------------------+------+-------------+-----------+-------------+------------------------------------------------+ | mysqld-relay-bin.000002 | 4 | Format_desc | 2 | 120 | Server ver: 5.6.31-log, Binlog ver: 4 | | mysqld-relay-bin.000002 | 120 | Rotate | 1 | 0 | mysql-bin.000001;pos=120 | | mysqld-relay-bin.000002 | 167 | Format_desc | 1 | 0 | Server ver: 5.6.31-log, Binlog ver: 4 | | mysqld-relay-bin.000002 | 283 | Query | 1 | 238 | create table sbtest.b(id int,name varchar(10)) | | mysqld-relay-bin.000002 | 401 | Query | 1 | 315 | BEGIN | | mysqld-relay-bin.000002 | 478 | Query | 1 | 421 | insert into sbtest.b values(1,'a') | | mysqld-relay-bin.000002 | 584 | Xid | 1 | 452 | COMMIT /* xid=102 */ | | mysqld-relay-bin.000002 | 615 | Query | 1 | 529 | BEGIN | | mysqld-relay-bin.000002 | 692 | Query | 1 | 635 | insert into sbtest.b values(2,'b') | | mysqld-relay-bin.000002 | 798 | Xid | 1 | 666 | COMMIT /* xid=103 */ | | mysqld-relay-bin.000002 | 829 | Query | 1 | 743 | BEGIN | | mysqld-relay-bin.000002 | 906 | Query | 1 | 849 | insert into sbtest.b values(3,'c') | | mysqld-relay-bin.000002 | 1012 | Xid | 1 | 880 | COMMIT /* xid=104 */ | | mysqld-relay-bin.000002 | 1043 | Query | 1 | 957 | BEGIN | | mysqld-relay-bin.000002 | 1120 | Query | 1 | 1063 | insert into sbtest.b values(4,'d') | | mysqld-relay-bin.000002 | 1226 | Xid | 1 | 1094 | COMMIT /* xid=105 */ | | mysqld-relay-bin.000002 | 1257 | Query | 1 | 1171 | BEGIN | | mysqld-relay-bin.000002 | 1334 | Query | 1 | 1277 | insert into sbtest.b values(5,'e') | | mysqld-relay-bin.000002 | 1440 | Xid | 1 | 1308 | COMMIT /* xid=106 */ | +-------------------------+------+-------------+-----------+-------------+------------------------------------------------+ 19 rows in set (0.00 sec)
通过对比master中的binlog event，可以看到show relaylog events中的End_log_pos实际上指的是对应的二进制事件在binlog的位置。
再来查看Candicate master中对应的relay log的内容
[root@node2 mysql]# mysqlbinlog mysqld-relay-bin.000002
[root@node2 mysql]# mysqlbinlog mysqld-relay-bin.000002 /*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/; /*!40019 SET @@session.max_insert_delayed_threads=0*/; /*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/; DELIMITER /*!*/; # at 4 #170524 17:16:37 server id 2 end_log_pos 120 CRC32 0x4faba9ae Start: binlog v 4, server v 5.6.31-log created 170524 17:16:37 BINLOG ' dU8lWQ8CAAAAdAAAAHgAAABAAAQANS42LjMxLWxvZwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAEzgNAAgAEgAEBAQEEgAAXAAEGggAAAAICAgCAAAACgoKGRkAAa6p q08= '/*!*/; # at 120 #700101 8:00:00 server id 1 end_log_pos 0 CRC32 0x74c6d70c Rotate to mysql-bin.000001 pos: 120 # at 167 #170524 17:15:49 server id 1 end_log_pos 0 CRC32 0xed2672eb Start: binlog v 4, server v 5.6.31-log created 170524 17:15:49 BINLOG ' RU8lWQ8BAAAAdAAAAAAAAAAAAAQANS42LjMxLWxvZwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAEzgNAAgAEgAEBAQEEgAAXAAEGggAAAAICAgCAAAACgoKGRkAAety Ju0= '/*!*/; # at 283 #170524 17:17:20 server id 1 end_log_pos 238 CRC32 0xdd48c118 Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617440/*!*/; SET @@session.pseudo_thread_id=2/*!*/; SET @@session.foreign_key_checks=1, @@session.sql_auto_is_null=0, @@session.unique_checks=1, @@session.autocommit=1/*!*/; SET @@session.sql_mode=1075838976/*!*/; SET @@session.auto_increment_increment=1, @@session.auto_increment_offset=1/*!*/; /*!C utf8 *//*!*/; SET @@session.character_set_client=33,@@session.collation_connection=33,@@session.collation_server=33/*!*/; SET @@session.lc_time_names=0/*!*/; SET @@session.collation_database=DEFAULT/*!*/; create table sbtest.b(id int,name varchar(10)) /*!*/; # at 401 #170524 17:17:27 server id 1 end_log_pos 315 CRC32 0xae393750 Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617447/*!*/; BEGIN /*!*/; # at 478 #170524 17:17:27 server id 1 end_log_pos 421 CRC32 0x28a781ae Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617447/*!*/; insert into sbtest.b values(1,'a') /*!*/; # at 584 #170524 17:17:27 server id 1 end_log_pos 452 CRC32 0x680f1bfe Xid = 29 COMMIT/*!*/; # at 615 #170524 17:17:33 server id 1 end_log_pos 529 CRC32 0x6a1aae7e Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617453/*!*/; BEGIN /*!*/; # at 692 #170524 17:17:33 server id 1 end_log_pos 635 CRC32 0x117786ca Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617453/*!*/; insert into sbtest.b values(2,'b') /*!*/; # at 798 #170524 17:17:33 server id 1 end_log_pos 666 CRC32 0xa8400ec6 Xid = 30 COMMIT/*!*/; # at 829 #170524 17:17:38 server id 1 end_log_pos 743 CRC32 0x24f9a1d2 Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617458/*!*/; BEGIN /*!*/; # at 906 #170524 17:17:38 server id 1 end_log_pos 849 CRC32 0x56fa9e89 Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617458/*!*/; insert into sbtest.b values(3,'c') /*!*/; # at 1012 #170524 17:17:38 server id 1 end_log_pos 880 CRC32 0x2ac656d4 Xid = 31 COMMIT/*!*/; # at 1043 #170524 17:17:44 server id 1 end_log_pos 957 CRC32 0x73a903bf Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617464/*!*/; BEGIN /*!*/; # at 1120 #170524 17:17:44 server id 1 end_log_pos 1063 CRC32 0x171b9b27 Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617464/*!*/; insert into sbtest.b values(4,'d') /*!*/; # at 1226 #170524 17:17:44 server id 1 end_log_pos 1094 CRC32 0x47d6fe57 Xid = 32 COMMIT/*!*/; # at 1257 #170524 17:17:49 server id 1 end_log_pos 1171 CRC32 0x2d37da37 Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617469/*!*/; BEGIN /*!*/; # at 1334 #170524 17:17:49 server id 1 end_log_pos 1277 CRC32 0xd2201fa2 Query thread_id=2 exec_time=0 error_code=0 SET TIMESTAMP=1495617469/*!*/; insert into sbtest.b values(5,'e') /*!*/; # at 1440 #170524 17:17:49 server id 1 end_log_pos 1308 CRC32 0xac1b464e Xid = 33 COMMIT/*!*/; DELIMITER ; # End of log file ROLLBACK /* added by mysqlbinlog */; /*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/; /*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;
View Code
mysql中binlog有个有意思的地方是，位置点其实是也是字节的大小。
譬如，上面这个relay log中，最后一个位点是# at 1440，算上最后一个commit操作需占用31个字节，所以整个文件的大小是1471，与实际大小吻合。
[root@node2 mysql]# ll mysqld-relay-bin.000002 -rw-rw---- 1 mysql mysql 1471 May 24 17:17 mysqld-relay-bin.000002
mysql> show slave statusG
*************************** 1. row ***************************
Slave_IO_State: Waitingfor master to send event
Master_Host:192.168.244.10
Master_User: repl
Master_Port:3306
Connect_Retry:60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos:1308
Relay_Log_File: mysqld-relay-bin.000002
Relay_Log_Pos:1471
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno:0
Last_Error:
Skip_Counter:0
Exec_Master_Log_Pos:1308
Relay_Log_Space:1645
Until_Condition: None
Until_Log_File:
Until_Log_Pos:0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master:0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno:0
Last_IO_Error:
Last_SQL_Errno:0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id:1
Master_UUID: 2a6365e0-1d05-11e7-956d-000c29c64704
Master_Info_File:/var/lib/mysql/master.info
SQL_Delay:0
SQL_Remaining_Delay:NULL
Slave_SQL_Running_State: Slave hasread all relay log; waiting for the slave I/O thread to update it
Master_Retry_Count:86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position:0
1 row in set (0.00 sec)
待会儿需要修改上面Master_Log_File,Read_Master_Log_Pos,Relay_Log_File,Relay_Log_Pos,Relay_Master_Log_File,Exec_Master_Log_Pos的值。
虽然这几个参数的值与master.info和relay-log.info文件是相对应的，
但通过修改master.info和relay-log.info的值，并重启slave，并不会将上述几个参数值修改。
上述几个参数是保存到内存中的，唯一可行的方案是首先关闭slave实例，再修改master.info和relay-log.info文件，然后重新启动mysql实例。
关闭实例
[root@node2 mysql]# service mysqld stop
剪裁relay log
这里，写了个python脚本实现该功能
#!/usr/bin/python
f1= open(‘mysqld-relay-bin.000002′,’r’)
f2= open(‘tmp_relay_bin’,’w+’)
size1=f1.read(615)
f2.write(size1)
f1.seek(1471)
size2=f1.read()
f2.write(size2)
f1.close()
f2.close()
在上述脚本size1中，615对应的是insert into sbtest.b values(1,’a’)这条记录
[root@node2 mysql]# python 1.py
[root@node2 mysql]# mv tmp_relay_bin mysqld-relay-bin.000002
修改master.info的内容
主要是修改第三行
23 mysql-bin.000001 1308
修改为
23 mysql-bin.000001 452
修改relay-log.info的内容
原文件如下：
7 ./mysqld-relay-bin.000002 1471 mysql-bin.000001 1308 0 0 1
修改为：
7 ./mysqld-relay-bin.000002 615 mysql-bin.000001 452 0 0 1
启动slave，注意，配置文件中必须设置skip-slave-start，不然它自动开启主从复制。
[root@node2 mysql]# service mysqld start
#!/usr/bin/python
f1 = open('mysqld-relay-bin.000002','r')
f2 = open('tmp_relay_bin','w+')
size1=f1.read(1043)
f2.write(size1)
f1.seek(1471)
size2=f1.read()
f2.write(size2)
f1.close()
f2.close()
1043对应的是insert into sbtest.b values(3,’c’)这条记录
修改master.info的内容
23 mysql-bin.000001 880
修改relay-log.info的内容
7 ./mysqld-relay-bin.000002 1043 mysql-bin.000001 880 0 0 1
# nohup masterha_manager –conf=/etc/masterha/app1.cnf –remove_dead_master_conf –ignore_last_failover
/masterha/app1/manager.log 2>&1 &
# masterha_check_status –conf=/etc/masterha/app1.cnf
app1 (pid:1615) is running(0:PING_OK), master:192.168.244.10
# service mysqld stop
该日志的时间点与上面relay log的时间点并不吻合，原因在于这个反复测试了很多次。
Sun May 21 20:50:46 2017 – [warning] Got error on MySQL connect: 2013 (Lost connection to MySQL server at ‘reading initial communication packet’, system error: 111)
Sun May21 20:50:46 2017 – [warning] Connection failed 1 time(s)..
Sun May21 20:50:46 2017 – [info] Executing secondary network check script: /usr/local/bin/masterha_secondary_check -s 192.168.244.20 -s 192.168.244.30 –user=root –master_host=192.168.244.10 –master_ip=192.168.244.10 –master_port=3306 –user=root –master_host=192.168.244.10 –master_ip=192.168.244.10 –master_port=3306 –master_user=monitor –master_password=monitor123 –ping_type=SELECT
Sun May21 20:50:46 2017 – [info] Executing SSH check script: save_binary_logs –command=test –start_pos=4 –binlog_dir=/var/lib/mysql –output_file=/tmp/save_binary_logs_test –manager_version=0.56 –binlog_prefix=mysql-bin
Monitoring server192.168.244.20 is reachable, Master is not reachable from 192.168.244.20. OK.
Sun May21 20:50:46 2017 – [info] HealthCheck: SSH to 192.168.244.10 is reachable.
Monitoring server192.168.244.30 is reachable, Master is not reachable from 192.168.244.30. OK.
— 当monitor检测到master mysqld不可用的时候，即根据masterha_secondary_check脚本从Candicate master和Slave上判断master mysqld的可用性，
根据上面的显示信息，通过192.168.244.20和192.168.244.30也判断到master mysqld不可用。
如果任意一个slave判断到master mysqld可用，则输出的信息如下：
#/usr/local/bin/masterha_secondary_check -s 192.168.244.20 -s 192.168.244.30 –user=root –master_host=192.168.244.10 –master_ip=192.168.244.10 –master_port=3306
Master is reachable from192.168.244.20!
Sun May21 20:50:46 2017 – [info] Master is not reachable from all other monitoring servers. Failover should start.
Sun May21 20:50:47 2017 – [warning] Got error on MySQL connect: 2013 (Lost connection to MySQL server at ‘reading initial communication packet’, system error: 111)
Sun May21 20:50:47 2017 – [warning] Connection failed 2 time(s)..
Sun May21 20:50:48 2017 – [warning] Got error on MySQL connect: 2013 (Lost connection to MySQL server at ‘reading initial communication packet’, system error: 111)
Sun May21 20:50:48 2017 – [warning] Connection failed 3 time(s)..
Sun May21 20:50:49 2017 – [warning] Got error on MySQL connect: 2013 (Lost connection to MySQL server at ‘reading initial communication packet’, system error: 111)
Sun May21 20:50:49 2017 – [warning] Connection failed 4 time(s)..
Sun May21 20:50:49 2017 – [warning] Master is not reachable from health checker!
Sun May21 20:50:49 2017 – [warning] Master 192.168.244.10(192.168.244.10:3306) is not reachable!
Sun May21 20:50:49 2017 – [warning] SSH is reachable.
— 一共判断了4次，均判断master mysqld不可用，但是master主机通过ssh还是能登录上去。
如果这里显示的是SSH is NOT reachable，则代表master主机也已经宕机了，
刚开始还以为是通过ssh来判断主机是否宕机，但在之前的测试方案中（具体可见文末），master并没有宕机，这里却显示SSH is NOT reachable.
通过上面的输出才知道是通过save_binary_logs脚本来判断ssh可用性的。
Sun May21 20:50:49 2017 – [info] Connecting to a master server failed. Reading configuration file /etc/masterha_default.cnf and /etc/masterha/app1.cnf again, and trying to connect to all servers to check server status..
Sun May21 20:50:49 2017 – [warning] Global configuration file /etc/masterha_default.cnf not found. Skipping.
Sun May21 20:50:49 2017 – [info] Reading application default configuration from /etc/masterha/app1.cnf..
Sun May21 20:50:49 2017 – [info] Reading server configuration from /etc/masterha/app1.cnf..
Sun May21 20:50:50 2017 – [warning] SQL Thread is stopped(no error) on 192.168.244.20(192.168.244.20:3306)
Sun May21 20:50:50 2017 – [warning] SQL Thread is stopped(no error) on 192.168.244.30(192.168.244.30:3306)
Sun May21 20:50:50 2017 – [info] GTID failover mode = 0
Sun May21 20:50:50 2017 – [info] Dead Servers:
Sun May21 20:50:50 2017 – [info] 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:50 2017 – [info] Alive Servers:
Sun May21 20:50:50 2017 – [info] 192.168.244.20(192.168.244.20:3306)
Sun May21 20:50:50 2017 – [info] 192.168.244.30(192.168.244.30:3306)
Sun May21 20:50:50 2017 – [info] Alive Slaves:
Sun May21 20:50:50 2017 – [info] 192.168.244.20(192.168.244.20:3306) Version=5.6.31-log (oldest major version between slaves) log-bin:enabled
Sun May21 20:50:50 2017 – [info] Replicating from 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:50 2017 – [info] Primary candidate for the new Master (candidate_master is set)
Sun May21 20:50:50 2017 – [info] 192.168.244.30(192.168.244.30:3306) Version=5.6.31-log (oldest major version between slaves) log-bin:enabled
Sun May21 20:50:50 2017 – [info] Replicating from 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:50 2017 – [info] Checking slave configurations..
Sun May21 20:50:50 2017 – [info] Checking replication filtering settings..
Sun May21 20:50:50 2017 – [info] Replication filtering check ok.
Sun May21 20:50:50 2017 – [info] Master is down!
Sun May21 20:50:50 2017 – [info] Terminating monitoring script.
Sun May21 20:50:50 2017 – [info] Got exit code 20 (Master dead).
Sun May21 20:50:50 2017 – [info] MHA::MasterFailover version 0.56.
Sun May21 20:50:50 2017 – [info] Starting master failover.
— 读取MHA的配置文件，检查slave的相关配置，比如read_only参数，是否设置了复制的过滤规则
从上面的输出中可以看出，SQL Thread正常停止了并不影响MHA的切换。
Sun May21 20:50:50 2017 – [info]
Sun May21 20:50:50 2017 – [info] * Phase 1: Configuration Check Phase..
Sun May21 20:50:50 2017 – [info]
Sun May21 20:50:51 2017 – [warning] SQL Thread is stopped(no error) on 192.168.244.20(192.168.244.20:3306)
Sun May21 20:50:51 2017 – [warning] SQL Thread is stopped(no error) on 192.168.244.30(192.168.244.30:3306)
Sun May21 20:50:51 2017 – [info] GTID failover mode = 0
Sun May21 20:50:51 2017 – [info] Dead Servers:
Sun May21 20:50:51 2017 – [info] 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:51 2017 – [info] Checking master reachability via MySQL(double check)…
Sun May21 20:50:51 2017 – [info] ok.
Sun May21 20:50:51 2017 – [info] Alive Servers:
Sun May21 20:50:51 2017 – [info] 192.168.244.20(192.168.244.20:3306)
Sun May21 20:50:51 2017 – [info] 192.168.244.30(192.168.244.30:3306)
Sun May21 20:50:51 2017 – [info] Alive Slaves:
Sun May21 20:50:51 2017 – [info] 192.168.244.20(192.168.244.20:3306) Version=5.6.31-log (oldest major version between slaves) log-bin:enabled
Sun May21 20:50:51 2017 – [info] Replicating from 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:51 2017 – [info] Primary candidate for the new Master (candidate_master is set)
Sun May21 20:50:51 2017 – [info] 192.168.244.30(192.168.244.30:3306) Version=5.6.31-log (oldest major version between slaves) log-bin:enabled
Sun May21 20:50:51 2017 – [info] Replicating from 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:51 2017 – [info] Starting SQL thread on 192.168.244.20(192.168.244.20:3306) ..
Sun May21 20:50:51 2017 – [info] done.
Sun May21 20:50:51 2017 – [info] Starting SQL thread on 192.168.244.30(192.168.244.30:3306) ..
Sun May21 20:50:51 2017 – [info] done.
Sun May21 20:50:51 2017 – [info] Starting Non-GTID based failover.
Sun May21 20:50:51 2017 – [info]
Sun May21 20:50:51 2017 – [info] ** Phase 1: Configuration Check Phase completed.
— 第一阶段，检查了MHA的配置信息，并再次判断了master的可用性。
第二阶段，关闭dead master。
包括执行摘除master上的vip，同时执行shutdown_script脚本，因为该脚本在配置文件中没有定义，故跳过。
Sun May21 20:50:51 2017 – [info]
Sun May21 20:50:51 2017 – [info] * Phase 2: Dead Master Shutdown Phase..
Sun May21 20:50:51 2017 – [info]
Sun May21 20:50:51 2017 – [info] Forcing shutdown so that applications never connect to the current master..
Sun May21 20:50:51 2017 – [info] Executing master IP deactivation script:
Sun May21 20:50:51 2017 – [info] /usr/local/bin/master_ip_failover –orig_master_host=192.168.244.10 –orig_master_ip=192.168.244.10 –orig_master_port=3306 –command=stopssh –ssh_user=root
Disabling the VIP an old master:192.168.244.10
SIOCSIFFLAGS: Cannot assign requested address
Sun May21 20:50:51 2017 – [info] done.
Sun May21 20:50:51 2017 – [warning] shutdown_script is not set. Skipping explicit shutting down of the dead master.
Sun May21 20:50:51 2017 – [info] * Phase 2: Dead Master Shutdown Phase completed.
Sun May21 20:50:51 2017 – [info]
— 第三阶段
3.1 判断哪个slave的二进制日志是最新的。
通过下面的输出可以看出，所有的slave中，最新的二进制日志位置是mysql-bin.000001:880（通过show slave status中的Master_Log_File, Read_Master_Log_Pos得到）
最旧的二进制日志位置是mysql-bin.000001:452
Sun May21 20:50:51 2017 – [info] * Phase 3: Master Recovery Phase..
Sun May21 20:50:51 2017 – [info]
Sun May21 20:50:51 2017 – [info] * Phase 3.1: Getting Latest Slaves Phase..
Sun May21 20:50:51 2017 – [info]
Sun May21 20:50:51 2017 – [info] The latest binary log file/position on all slaves is mysql-bin.000001:880
Sun May21 20:50:51 2017 – [info] Latest slaves (Slaves that received relay log files to the latest):
Sun May21 20:50:51 2017 – [info] 192.168.244.30(192.168.244.30:3306) Version=5.6.31-log (oldest major version between slaves) log-bin:enabled
Sun May21 20:50:51 2017 – [info] Replicating from 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:51 2017 – [info] The oldest binary log file/position on all slaves is mysql-bin.000001:452
Sun May21 20:50:51 2017 – [info] Oldest slaves:
Sun May21 20:50:51 2017 – [info] 192.168.244.20(192.168.244.20:3306) Version=5.6.31-log (oldest major version between slaves) log-bin:enabled
Sun May21 20:50:51 2017 – [info] Replicating from 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:51 2017 – [info] Primary candidate for the new Master (candidate_master is set)
Sun May21 20:50:51 2017 – [info]
— 3.2 保存master的binlog
注意，上面已经判断到slave中最新二进制日志是mysql-bin.000001:880，所以它把该位置后所有二进制日志都拼接起来，并scp到monitor的/masterha/app1目录下。
Sun May21 20:50:51 2017 – [info] * Phase 3.2: Saving Dead Master’s Binlog Phase..
Sun May 21 20:50:51 2017 – [info]
Sun May21 20:50:52 2017 – [info] Fetching dead master’s binary logs..
Sun May 21 20:50:52 2017 – [info] Executing command on the dead master 192.168.244.10(192.168.244.10:3306): save_binary_logs –command=save –start_file=mysql-bin.000001 –start_pos=880 –binlog_dir=/var/lib/mysql –output_file=/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog –handle_raw_binlog=1 –disable_log_bin=0 –manager_version=0.56
Creating/tmp if not exists.. ok.
Concat binary/relay logs from mysql-bin.000001 pos 880 to mysql-bin.000001 EOF into /tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog ..
Binlog Checksum enabled
Dumping binlog format description event, from position0 to 120.. ok.
Dumping effective binlog data from/var/lib/mysql/mysql-bin.000001 position 880 to tail(1308).. ok.
Binlog Checksum enabled
Concat succeeded.
Sun May21 20:50:52 2017 – [info] scp from root@192.168.244.10:/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog to local:/masterha/app1/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog succeeded.
Sun May21 20:50:52 2017 – [info] HealthCheck: SSH to 192.168.244.20 is reachable.
Sun May21 20:50:53 2017 – [info] HealthCheck: SSH to 192.168.244.30 is reachable.
Sun May21 20:50:53 2017 – [info]
— 3.3 选新主阶段
首先判断最新的slave中是否包括最旧的二进制日志（mysql-bin.000001:452）以后的relay log。
接着选新主，
因为192.168.244.20中设置了candidate_master设置了，所以192.168.244.20被指定为新主。
Sun May21 20:50:53 2017 – [info] * Phase 3.3: Determining New Master Phase..
Sun May21 20:50:53 2017 – [info]
Sun May21 20:50:53 2017 – [info] Finding the latest slave that has all relay logs for recovering other slaves..
Sun May21 20:50:53 2017 – [info] Checking whether 192.168.244.30 has relay logs from the oldest position..
Sun May21 20:50:53 2017 – [info] Executing command: apply_diff_relay_logs –command=find –latest_mlf=mysql-bin.000001 –latest_rmlp=880 –target_mlf=mysql-bin.000001 –target_rmlp=452 –server_id=3 –workdir=/tmp –timestamp=20170521205050 –manager_version=0.56 –relay_log_info=/var/lib/mysql/relay-log.info –relay_dir=/var/lib/mysql/ :
Opening/var/lib/mysql/relay-log.info … ok.
Relay log found at/var/lib/mysql, up to mysqld-relay-bin.000003
Fast relay log position search failed. Reading relay logs tofind..
Reading mysqld-relay-bin.000003
Binlog Checksum enabled
Reading mysqld-relay-bin.000002
Binlog Checksum enabled
Master Version is5.6.31-log
Binlog Checksum enabled
mysqld-relay-bin.000002 contains master mysql-bin.000001 from position 120
Target relay log FOUND!
Sun May21 20:50:53 2017 – [info] OK. 192.168.244.30 has all relay logs.
Sun May21 20:50:53 2017 – [info] Searching new master from slaves..
Sun May21 20:50:53 2017 – [info] Candidate masters from the configuration file:
Sun May21 20:50:53 2017 – [info] 192.168.244.20(192.168.244.20:3306) Version=5.6.31-log (oldest major version between slaves) log-bin:enabled
Sun May21 20:50:53 2017 – [info] Replicating from 192.168.244.10(192.168.244.10:3306)
Sun May21 20:50:53 2017 – [info] Primary candidate for the new Master (candidate_master is set)
Sun May21 20:50:53 2017 – [info] Non-candidate masters:
Sun May21 20:50:53 2017 – [info] Searching from candidate_master slaves which have received the latest relay log events..
Sun May21 20:50:53 2017 – [info] Not found.
Sun May21 20:50:53 2017 – [info] Searching from all candidate_master slaves..
Sun May21 20:50:53 2017 – [info] New master is 192.168.244.20(192.168.244.20:3306)
Sun May21 20:50:53 2017 – [info] Starting master failover..
Sun May21 20:50:53 2017 – [info]
From:
192.168.244.10(192.168.244.10:3306) (current master)
+–192.168.244.20(192.168.244.20:3306)
+–192.168.244.30(192.168.244.30:3306)
To:
192.168.244.20(192.168.244.20:3306) (new master)
+–192.168.244.30(192.168.244.30:3306)
Sun May21 20:50:53 2017 – [info]
— 3.3 获取新主所需的差异二进制日志，包括两部分
1> 新主和最新的slave之间差异的relay log
2> 保存在MHA Manager上的最新的slave和原master之前差异的binlog
其中，差异的relay log通过如下方式获取：
ssh到192.168.244.30上，执行apply_diff_relay_logs获取差异的relay log。将差异的relay log scp到192.168.244.20。
Sun May21 20:50:53 2017 – [info] * Phase 3.3: New Master Diff Log Generation Phase..
Sun May21 20:50:53 2017 – [info]
Sun May21 20:50:53 2017 – [info] Server 192.168.244.20 received relay logs up to: mysql-bin.000001:452
Sun May21 20:50:53 2017 – [info] Need to get diffs from the latest slave(192.168.244.30) up to: mysql-bin.000001:880 (using the latest slave’s relay logs)
Sun May 21 20:50:53 2017 – [info] Connecting to the latest slave host 192.168.244.30, generating diff relay log files..
Sun May21 20:50:53 2017 – [info] Executing command: apply_diff_relay_logs –command=generate_and_send –scp_user=root –scp_host=192.168.244.20 –latest_mlf=mysql-bin.000001 –latest_rmlp=880 –target_mlf=mysql-bin.000001 –target_rmlp=452 –server_id=3 –diff_file_readtolatest=/tmp/relay_from_read_to_latest_192.168.244.20_3306_20170521205050.binlog –workdir=/tmp –timestamp=20170521205050 –handle_raw_binlog=1 –disable_log_bin=0 –manager_version=0.56 –relay_log_info=/var/lib/mysql/relay-log.info –relay_dir=/var/lib/mysql/
Sun May21 20:50:54 2017 – [info]
Opening/var/lib/mysql/relay-log.info … ok.
Relay log found at/var/lib/mysql, up to mysqld-relay-bin.000003
Fast relay log position search failed. Reading relay logs tofind..
Reading mysqld-relay-bin.000003
Binlog Checksum enabled
Reading mysqld-relay-bin.000002
Binlog Checksum enabled
Master Version is5.6.31-log
Binlog Checksum enabled
mysqld-relay-bin.000002 contains master mysql-bin.000001 from position 120
Target relay logfile/position found. start_file:mysqld-relay-bin.000002, start_pos:615.
Concat binary/relay logs from mysqld-relay-bin.000002 pos 615 to mysqld-relay-bin.000003 EOF into /tmp/relay_from_read_to_latest_192.168.244.20_3306_20170521205050.binlog ..
Binlog Checksum enabled
Binlog Checksum enabled
Dumping binlog format description event, from position0 to 283.. ok.
Dumping effective binlog data from/var/lib/mysql/mysqld-relay-bin.000002 position 615 to tail(1066).. ok.
Dumping binloghead events (rotate events), skipping format description events from /var/lib/mysql/mysqld-relay-bin.000003.. Binlog Checksum enabled
dumped up to pos120. ok.
No need to dump effective binlog data from/var/lib/mysql/mysqld-relay-bin.000003 (pos starts 120, filesize 120). Skipping.
Binlog Checksum enabled
Binlog Checksum enabled
Concat succeeded.
Generatingdiff relay log succeeded. Saved at /tmp/relay_from_read_to_latest_192.168.244.20_3306_20170521205050.binlog .
scp node3:/tmp/relay_from_read_to_latest_192.168.244.20_3306_20170521205050.binlog to root@192.168.244.20(22) succeeded.
Sun May21 20:50:54 2017 – [info] Generating diff files succeeded.
Sun May21 20:50:54 2017 – [info] Sending binlog..
Sun May21 20:50:54 2017 – [info] scp from local:/masterha/app1/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog to root@192.168.244.20:/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog succeeded.
Sun May21 20:50:54 2017 – [info]
— 3.4 应用从master保存的二进制日志事件
首先，等原来的所有的relay log都应用完。
其次，再通过apply_diff_relay_logs应用差异的relay log，及差异的binlog。
应用完毕后，得到新的master binlog的文件和位置，其它slave可根据该文件和位置来建立主从复制关系。
第三，执行master_ip_failover脚本，执行如下操作
1> 将新主的read_only设置为0
2> 启动vip
Sun May21 20:50:54 2017 – [info] * Phase 3.4: Master Log Apply Phase..
Sun May21 20:50:54 2017 – [info]
Sun May21 20:50:54 2017 – [info] *NOTICE: If any error happens from this phase, manual recovery is needed.
Sun May21 20:50:54 2017 – [info] Starting recovery on 192.168.244.20(192.168.244.20:3306)..
Sun May21 20:50:54 2017 – [info] Generating diffs succeeded.
Sun May21 20:50:54 2017 – [info] Waiting until all relay logs are applied.
Sun May21 20:50:54 2017 – [info] done.
Sun May21 20:50:54 2017 – [info] Getting slave status..
Sun May21 20:50:54 2017 – [info] This slave(192.168.244.20)’s Exec_Master_Log_Pos equals to Read_Master_Log_Pos(mysql-bin.000001:452). No need to recover from Exec_Master_Log_Pos.
Sun May 21 20:50:54 2017 – [info] Connecting to the target slave host 192.168.244.20, running recover script..
Sun May21 20:50:54 2017 – [info] Executing command: apply_diff_relay_logs –command=apply –slave_user=’monitor’ –slave_host=192.168.244.20 –slave_ip=192.168.244.20 –slave_port=3306 –apply_files=/tmp/relay_from_read_to_latest_192.168.244.20_3306_20170521205050.binlog,/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog –workdir=/tmp –target_version=5.6.31-log –timestamp=20170521205050 –handle_raw_binlog=1 –disable_log_bin=0 –manager_version=0.56 –slave_pass=xxx
Sun May21 20:50:55 2017 – [info]
Concat all apply files to/tmp/total_binlog_for_192.168.244.20_3306.20170521205050.binlog ..
Copying the first binlogfile /tmp/relay_from_read_to_latest_192.168.244.20_3306_20170521205050.binlog to /tmp/total_binlog_for_192.168.244.20_3306.20170521205050.binlog.. ok.
Dumping binloghead events (rotate events), skipping format description events from /tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog.. Binlog Checksum enabled
dumped up to pos120. ok.
/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog has effective binlog events from pos 120.
Dumping effective binlog data from/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog position 120 to tail(548).. ok.
Concat succeeded.
All apply target binary logs are concatinated at/tmp/total_binlog_for_192.168.244.20_3306.20170521205050.binlog .
MySQL client version is5.6.31. Using –binary-mode.
Applying differential binary/relay log files /tmp/relay_from_read_to_latest_192.168.244.20_3306_20170521205050.binlog,/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog on 192.168.244.20:3306. This may take long time…
Applying log files succeeded.
Sun May21 20:50:55 2017 – [info] All relay logs were successfully applied.
Sun May21 20:50:55 2017 – [info] Getting new master’s binlog name and position..
Sun May 21 20:50:55 2017 – [info] mysql-bin.000002:976
Sun May21 20:50:55 2017 – [info] All other slaves should start replication from here. Statement should be: CHANGE MASTER TO MASTER_HOST=’192.168.244.20′, MASTER_PORT=3306, MASTER_LOG_FILE=’mysql-bin.000002′, MASTER_LOG_POS=976, MASTER_USER=’repl’, MASTER_PASSWORD=’xxx’;
Sun May21 20:50:55 2017 – [info] Executing master IP activate script:
Sun May21 20:50:55 2017 – [info] /usr/local/bin/master_ip_failover –command=start –ssh_user=root –orig_master_host=192.168.244.10 –orig_master_ip=192.168.244.10 –orig_master_port=3306 –new_master_host=192.168.244.20 –new_master_ip=192.168.244.20 –new_master_port=3306 –new_master_user=’monitor’ –new_master_password=’monitor123′
Set read_only=0 on the new master.
Enabling the VIP192.168.244.188 on the new master: 192.168.244.20
Sun May21 20:50:55 2017 – [info] OK.
Sun May21 20:50:55 2017 – [info] ** Finished master recovery successfully.
Sun May21 20:50:55 2017 – [info] * Phase 3: Master Recovery Phase completed.
— 第四阶段 slave恢复阶段
— 4.1 因为192.168.244.30拥有最新的relay log，所以也没必要获取差异的relay log
— 4.2 开始slave的恢复阶段
1> 将monitor上保存的master上的差异的二进制日志scp到slave上。
2> 应用差异日志。
3> 清除原来的复制关系，并再次执行change master命令建立新的主从同步。
如果有多个slave，则该恢复过程是并行的。
Sun May21 20:50:55 2017 – [info]
Sun May21 20:50:55 2017 – [info] * Phase 4: Slaves Recovery Phase..
Sun May21 20:50:55 2017 – [info]
Sun May21 20:50:55 2017 – [info] * Phase 4.1: Starting Parallel Slave Diff Log Generation Phase..
Sun May21 20:50:55 2017 – [info]
Sun May21 20:50:55 2017 – [info] — Slave diff file generation on host 192.168.244.30(192.168.244.30:3306) started, pid: 4966. Check tmp log /masterha/app1/192.168.244.30_3306_20170521205050.log if it takes time..
Sun May21 20:50:56 2017 – [info]
Sun May21 20:50:56 2017 – [info] Log messages from 192.168.244.30 …
Sun May21 20:50:56 2017 – [info]
Sun May21 20:50:55 2017 – [info] This server has all relay logs. No need to generate diff files from the latest slave.
Sun May21 20:50:56 2017 – [info] End of log messages from 192.168.244.30.
Sun May21 20:50:56 2017 – [info] — 192.168.244.30(192.168.244.30:3306) has the latest relay log events.
Sun May21 20:50:56 2017 – [info] Generating relay diff files from the latest slave succeeded.
Sun May21 20:50:56 2017 – [info]
Sun May21 20:50:56 2017 – [info] * Phase 4.2: Starting Parallel Slave Log Apply Phase..
Sun May21 20:50:56 2017 – [info]
Sun May21 20:50:56 2017 – [info] — Slave recovery on host 192.168.244.30(192.168.244.30:3306) started, pid: 4968. Check tmp log /masterha/app1/192.168.244.30_3306_20170521205050.log if it takes time..
Sun May21 20:50:58 2017 – [info]
Sun May21 20:50:58 2017 – [info] Log messages from 192.168.244.30 …
Sun May21 20:50:58 2017 – [info]
Sun May21 20:50:56 2017 – [info] Sending binlog..
Sun May21 20:50:57 2017 – [info] scp from local:/masterha/app1/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog to root@192.168.244.30:/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog succeeded.
Sun May21 20:50:57 2017 – [info] Starting recovery on 192.168.244.30(192.168.244.30:3306)..
Sun May21 20:50:57 2017 – [info] Generating diffs succeeded.
Sun May21 20:50:57 2017 – [info] Waiting until all relay logs are applied.
Sun May21 20:50:57 2017 – [info] done.
Sun May21 20:50:57 2017 – [info] Getting slave status..
Sun May21 20:50:57 2017 – [info] This slave(192.168.244.30)’s Exec_Master_Log_Pos equals to Read_Master_Log_Pos(mysql-bin.000001:880). No need to recover from Exec_Master_Log_Pos.
Sun May 21 20:50:57 2017 – [info] Connecting to the target slave host 192.168.244.30, running recover script..
Sun May21 20:50:57 2017 – [info] Executing command: apply_diff_relay_logs –command=apply –slave_user=’monitor’ –slave_host=192.168.244.30 –slave_ip=192.168.244.30 –slave_port=3306 –apply_files=/tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog –workdir=/tmp –target_version=5.6.31-log –timestamp=20170521205050 –handle_raw_binlog=1 –disable_log_bin=0 –manager_version=0.56 –slave_pass=xxx
Sun May21 20:50:57 2017 – [info]
MySQL client version is5.6.31. Using –binary-mode.
Applying differential binary/relay log files /tmp/saved_master_binlog_from_192.168.244.10_3306_20170521205050.binlog on 192.168.244.30:3306. This may take long time…
Applying log files succeeded.
Sun May21 20:50:57 2017 – [info] All relay logs were successfully applied.
Sun May21 20:50:57 2017 – [info] Resetting slave 192.168.244.30(192.168.244.30:3306) and starting replication from the new master 192.168.244.20(192.168.244.20:3306)..
Sun May21 20:50:58 2017 – [info] Executed CHANGE MASTER.
Sun May21 20:50:58 2017 – [info] Slave started.
Sun May21 20:50:58 2017 – [info] End of log messages from 192.168.244.30.
Sun May21 20:50:58 2017 – [info] — Slave recovery on host 192.168.244.30(192.168.244.30:3306) succeeded.
Sun May21 20:50:58 2017 – [info] All new slave servers recovered successfully.
— 第五阶段 清理阶段
从MHA的配置文件中剔除server1的配置信息
Sun May21 20:50:58 2017 – [info]
Sun May21 20:50:58 2017 – [info] * Phase 5: New master cleanup phase..
Sun May21 20:50:58 2017 – [info]
Sun May21 20:50:58 2017 – [info] Resetting slave info on the new master..
Sun May21 20:50:58 2017 – [info] 192.168.244.20: Resetting slave info succeeded.
Sun May21 20:50:58 2017 – [info] Master failover to 192.168.244.20(192.168.244.20:3306) completed successfully.
Sun May21 20:50:58 2017 – [info] Deleted server1 entry from /etc/masterha/app1.cnf .
Sun May21 20:50:58 2017 – [info]
— 生成 Failover 报告，发送告警邮件
—– Failover Report —–
app1: MySQL Master failover192.168.244.10(192.168.244.10:3306) to 192.168.244.20(192.168.244.20:3306) succeeded
Master192.168.244.10(192.168.244.10:3306) is down!
Check MHA Manager logs at node4:/masterha/app1/manager.log for details.
Started automated(non-interactive) failover.
Invalidated master IP address on192.168.244.10(192.168.244.10:3306)
The latest slave192.168.244.30(192.168.244.30:3306) has all relay logs for recovery.
Selected192.168.244.20(192.168.244.20:3306) as a new master.
192.168.244.20(192.168.244.20:3306): OK: Applying all logs succeeded.
192.168.244.20(192.168.244.20:3306): OK: Activated master IP address.
192.168.244.30(192.168.244.30:3306): This host has the latest relay log events.
Generating relaydiff files from the latest slave succeeded.
192.168.244.30(192.168.244.30:3306): OK: Applying all logs succeeded. Slave started, replicating from 192.168.244.20(192.168.244.20:3306)
192.168.244.20(192.168.244.20:3306): Resetting slave info succeeded.
Master failover to192.168.244.20(192.168.244.20:3306) completed successfully.
Sun May21 20:50:58 2017 – [info] Sending mail..
Unknown option: conf
同时判断MHA Manager到master的ssh可用性。
ssh可用性的判断结果影响后后续切换中的“Phase 3.2: Saving Dead Master’s Binlog Phase”
检查了MHA的配置信息，并再次判断了master的可用性。
宕机的master处理阶段，包括摘除VIP，执行shutdown_script中定义的脚本。
Phase 3.1: Getting Latest Slaves Phase..
判断哪个slave拥有最新的relay log（通过比较show slave status中的Master_Log_File, Read_Master_Log_Pos位置），
哪个slave拥有最旧的relay log
Phase 3.2: Saving Dead Master’s Binlog Phase..
根据上面得到的slave的最新位置信息，将差异的二进制日志保存到MHA Manager的指定目录下。
如果在第一步骤中，判断了MHA Manager到master的ssh不可用，则会跳过这个阶段。
Phase 3.3: Determining New Master Phase..
选择新的master
Phase 3.3: New Master Diff Log Generation Phase..
将差异的relay log和master差异日志scp到新的master上。
Phase 3.4: Master Log Apply Phase..
首先，等待slave上已有的relay log都应用完。
其次，通过apply_diff_relay_logs应用差异的relay log，及差异的binlog。
应用完毕后，得到新的master binlog的文件和位置，其它slave可根据该文件和位置来建立主从复制关系。
第三，执行master_ip_failover脚本，执行如下操作
1> 将新主的read_only设置为0
2> 启动vip
Phase 4.1: Starting Parallel Slave Diff Log Generation Phase
为slave获取差异的relay log
因为192.168.244.30拥有最新的relay log，所以也没必要获取差异的relay log
Phase 4.2: Starting Parallel Slave Log Apply Phase
开始slave的恢复阶段
1>将差异的relay log和master差异日志scp到slave上。
2> 应用差异日志。
3> 清除原来的复制关系，并再次执行change master命令建立新的主从同步。
如果有多个slave，则该恢复过程是并行的。
从MHA的配置文件中剔除server1的配置信息
： http://www.linuxidc.com/Linux/2017-05/144249p2.htm
