我們通常說的雙機熱備是指兩臺機器都在執行，但並不是兩臺機器都同時在提供服務。當提供服務的一臺出現故障的時候，另外一臺會馬上自動接管並且提供服務，而且切換的時間非常短。MySQL雙主複製，即互為Master-Slave(只有一個Master提供寫操作)，可以實現資料庫伺服器的熱備，但是一個Master當機後不能實現動態切換。使用Keepalived，可以通過虛擬IP，實現雙主對外的統一介面以及自動檢查、失敗切換機制，從而實現MySQL資料庫的高可用方案。之前梳理了Mysql主從/主主同步，下面說下Mysql+keeoalived雙主熱備高可用方案的實施。
Keepalived看名字就知道，保持存活，在網路裡面就是保持線上了，也就是所謂的高可用或熱備，用來防止單點故障（單點故障是指一旦某一點出現故障就會導 整個系統架構的不可用）的發生，那說到keepalived不得不說的一個協議不是VRRP協議，可以說這個協議就是keepalived實現的基礎。 1）Keepalived的工作原理是VRRP（Virtual Router Redundancy Protocol）虛擬路由冗餘協議。在VRRP中有兩組重要的概念：VRRP路由器和虛擬路由器，主控路由器和備份路由器。 2）VRRP路由器是指執行VRRP的路由器，是物理實體，虛擬路由器是指VRRP協議建立的，是邏輯概念。一組VRRP路由器協同工作，共同構成一臺虛擬路由器。 Vrrp中存在著一種選舉機制，用以選出提供服務的路由即主控路由，其他的則成了備份路由。當主控路由失效後，備份路由中會重新選舉出一個主控路由，來繼 續工作，來保障不間斷服務。
過多內容在這裡就不做詳細介紹了，下面詳細記錄下Mysql+Keepalived雙主熱備的高可用方案的操作記錄
1）先實施Master->Slave的主主同步。主主是資料雙向同步，主從是資料單向同步。一般情況下，主庫當機後，需要手動將連線切換到從庫上。（但是用keepalived就可以自動切換） 2）再結合Keepalived的使用，通過VIP實現Mysql雙主對外連線的統一介面。即客戶端通過Vip連線資料庫；當其中一臺當機後，VIP會漂移到另一臺上，這個過程對於客戶端的資料連線來說幾乎無感覺，從而實現高可用。
環境描述： mysql的安裝可以參考：http://www.cnblogs.com/kevingrace/p/6109679.html Centos6.8版本 Master1：182.148.15.238 安裝mysql和keepalived Master2: 182.148.15.237 安裝mysql和keepalived VIP：182.148.15.236 要實現主主同步，可以先實現主從同步，即master1->master2的主從同步，然後master2->master1的主從同步. 這樣，雙方就完成了主主同步。 注意下面幾點： 1）要保證同步服務期間之間的網路聯通。即能相互ping通，能使用對方授權資訊連線到對方資料庫（防火牆開放3306埠）。 2）關閉selinux。 3）同步前，雙方資料庫中需要同步的資料要保持一致。這樣，同步環境實現後，再次更新的資料就會如期同步了。
可能出現的問題
報錯： Last_IO_Error: Fatal error: The slave I/O thread stops because master and slave have equal MySQL server ids; these ids must be different for replication to work (or the --replicate-same-server-id option must be used on slave but this does not always make sense; please check the manual before using it). 解決辦法： 刪除mysql資料目錄下的auto.cnf檔案，重啟mysql服務即可！ 另：Keepalived必須使用root賬號啟動！！
一、Mysql主主同步環境部署
---------------master1伺服器操作記錄---------------
在my.cnf檔案的[mysqld]配置區域新增下面內容：
[root@master1 ~]# vim /usr/local/mysql/my.cnf
server-id = 1
log-bin = mysql-bin
sync_binlog = 1
binlog_checksum = none
binlog_format = mixed
auto-increment-increment = 2
auto-increment-offset = 1
slave-skip-errors = all
[root@master1 ~]# /etc/init.d/mysql restart
Shutting down MySQL. SUCCESS!
Starting MySQL.. SUCCESS!
資料同步授權（iptables防火牆開啟3306埠）這樣I/O執行緒就可以以這個使用者的身份連線到主伺服器，並且讀取它的二進位制日誌。
mysql> grant replication slave,replication client on *.* to wang@'182.148.15.%' identified by "wang@123";
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
最好將庫鎖住，僅僅允許讀，以保證資料一致性；待主主同步環境部署後再解鎖；
鎖住後，就不能往表裡寫資料，但是重啟mysql服務後就會自動解鎖！
mysql> flush tables with read lock; //注意該引數設定後，如果自己同步對方資料，同步前一定要記得先解鎖！
Query OK, 0 rows affected (0.00 sec)
檢視下log bin日誌和pos值位置
mysql> show master status;
+------------------+----------+--------------+--------------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------+-------------------+
| mysql-bin.000004 | 430 | | mysql,information_schema | |
+------------------+----------+--------------+--------------------------+-------------------+
1 row in set (0.00 sec)
---------------master2伺服器操作記錄---------------
在my.cnf檔案的[mysqld]配置區域新增下面內容：
[root@master2 ~]# vim /usr/local/mysql/my.cnf
server-id = 2
log-bin = mysql-bin
sync_binlog = 1
binlog_checksum = none
binlog_format = mixed
auto-increment-increment = 2
auto-increment-offset = 2
slave-skip-errors = all
[root@master2 ~]# /etc/init.d/mysql restart
Shutting down MySQL.. SUCCESS!
Starting MySQL.. SUCCESS!
mysql> grant replication slave,replication client on *.* to wang@'182.148.15.%' identified by "wang@123";
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> flush tables with read lock;
Query OK, 0 rows affected (0.00 sec)
mysql> show master status;
+------------------+----------+--------------+--------------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+--------------------------+-------------------+
| mysql-bin.000003 | 430 | | mysql,information_schema | |
+------------------+----------+--------------+--------------------------+-------------------+
1 row in set (0.00 sec)
---------------master1伺服器做同步操作---------------
mysql> unlock tables; //先解鎖，將對方資料同步到自己的資料庫中
mysql> slave stop；
mysql> change master to master_host='182.148.15.237',master_user='wang',master_password='wang@123',master_log_file='mysql-bin.000003',master_log_pos=430;
Query OK, 0 rows affected, 2 warnings (0.01 sec)
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
檢視同步狀態，如下出現兩個“Yes”，表明同步成功！
mysql> show slave status \G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 182.148.15.237
Master_User: wang
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003
Read_Master_Log_Pos: 430
Relay_Log_File: mysql-relay-bin.000002
Relay_Log_Pos: 279
Relay_Master_Log_File: mysql-bin.000003
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
.........................
Seconds_Behind_Master: 0
.........................
這樣，master1就和master2實現了主從同步，即master1同步master2的資料。
---------------master2伺服器做同步操作---------------
mysql> unlock tables; //先解鎖，將對方資料同步到自己的資料庫中
mysql> slave stop；
mysql> change master to master_host='182.148.15.238',master_user='wang',master_password='wang@123',master_log_file='mysql-bin.000004',master_log_pos=430;
Query OK, 0 rows affected, 2 warnings (0.06 sec)
mysql> start slave;
Query OK, 0 rows affected (0.01 sec)
mysql> show slave status \G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 182.148.15.238
Master_User: wang
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000004
Read_Master_Log_Pos: 430
Relay_Log_File: mysql-relay-bin.000002
Relay_Log_Pos: 279
Relay_Master_Log_File: mysql-bin.000004
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
........................
Seconds_Behind_Master: 0
........................
這樣，master2就和master1實現了主從同步，即master2也同步master1的資料。
以上表明雙方已經實現了mysql主主同步。
當執行一段時間後，要是發現同步有問題，比如只能單向同步，雙向同步失效。可以重新執行下上面的change master同步操作，只不過這樣同步後，只能同步在此之後的更新資料。下面開始進行資料驗證：
-----------------主主同步效果驗證---------------------
1）在master1資料庫上寫入新資料
mysql> unlock tables;
Query OK, 0 rows affected (0.00 sec)
mysql> create database huanqiu;
Query OK, 1 row affected (0.01 sec)
mysql> use huanqiu;
Database changed
mysql> create table if not exists haha (
-> id int(10) PRIMARY KEY AUTO_INCREMENT,
-> name varchar(50) NOT NULL);
Query OK, 0 rows affected (0.04 sec)
mysql> insert into haha values(1,"王士博");
Query OK, 1 row affected (0.00 sec)
mysql> insert into haha values(2,"郭慧慧");
Query OK, 1 row affected (0.00 sec)
mysql> select * from haha;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 王士博 |
| 2 | 郭慧慧 |
+----+-----------+
2 rows in set (0.00 sec)
然後在master2資料庫上檢視，發現資料已經同步過來了!
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| huanqiu |
| mysql |
| performance_schema |
| test |
+--------------------+
5 rows in set (0.00 sec)
mysql> use huanqiu;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+-------------------+
| Tables_in_huanqiu |
+-------------------+
| haha |
+-------------------+
1 row in set (0.00 sec)
mysql> select * from haha;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 王士博 |
| 2 | 郭慧慧 |
+----+-----------+
2 rows in set (0.00 sec)
2）在master2資料庫上寫入新資料
mysql> create database hehe;
Query OK, 1 row affected (0.00 sec)
mysql> insert into huanqiu.haha values(3,"周正"),(4,"李敏");
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
然後在master1資料庫上檢視，發現資料也已經同步過來了!
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| hehe |
| huanqiu |
| mysql |
| performance_schema |
| test |
+--------------------+
6 rows in set (0.00 sec)
mysql> select * from huanqiu.haha;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 王士博 |
| 2 | 郭慧慧 |
| 3 | 周正 |
| 4 | 李敏 |
+----+-----------+
4 rows in set (0.00 sec)
至此，Mysql主主同步環境已經實現。
二、配置Mysql+Keepalived故障轉移的高可用環境
1）安裝keepalived並將其配置成系統服務。master1和master2兩臺機器上同樣進行如下操作：
[root@master1 ~]# yum install -y openssl-devel
[root@master1 ~]# cd /usr/local/src/
[root@master1 src]# wget http://www.keepalived.org/software/keepalived-1.3.5.tar.gz
[root@master1 src]# tar -zvxf keepalived-1.3.5.tar.gz
[root@master1 src]# cd keepalived-1.3.5
[root@master1 keepalived-1.3.5]# ./configure --prefix=/usr/local/keepalived
[root@master1 keepalived-1.3.5]# make && make install
[root@master1 keepalived-1.3.5]# cp /usr/local/src/keepalived-1.3.5/keepalived/etc/init.d/keepalived /etc/rc.d/init.d/
[root@master1 keepalived-1.3.5]# cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
[root@master1 keepalived-1.3.5]# mkdir /etc/keepalived/
[root@master1 keepalived-1.3.5]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
[root@master1 keepalived-1.3.5]# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
[root@master1 keepalived-1.3.5]# echo "/etc/init.d/keepalived start" >> /etc/rc.local
2）master1機器上的keepalived.conf配置。（下面配置中沒有使用lvs的負載均衡功能，所以不需要配置虛擬伺服器virtual server）
[root@master1 ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@master1 ~]# vim /etc/keepalived/keepalived.conf ＃清空預設內容，直接採用下面配置：
! Configuration File for keepalived
global_defs {
notification_email {
ops@wangshibo.cn
tech@wangshibo.cn
}
notification_email_from ops@wangshibo.cn
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id MASTER-HA
}
vrrp_script chk_mysql_port { #檢測mysql服務是否在執行。有很多方式，比如程式，用指令碼檢測等等
script "/opt/chk_mysql.sh" #這裡通過指令碼監測
interval 2 #指令碼執行間隔，每2s檢測一次
weight -5 #指令碼結果導致的優先順序變更，檢測失敗（指令碼返回非0）則優先順序 -5
fall 2 #檢測連續2次失敗才算確定是真失敗。會用weight減少優先順序（1-255之間）
rise 1 #檢測1次成功就算成功。但不修改優先順序
}
vrrp_instance VI_1 {
state MASTER
interface eth0 #指定虛擬ip的網路卡介面
mcast_src_ip 182.148.15.238
virtual_router_id 51 #路由器標識，MASTER和BACKUP必須是一致的
priority 101 #定義優先順序，數字越大，優先順序越高，在同一個vrrp_instance下，MASTER的優先順序必須大於BACKUP的優先順序。這樣MASTER故障恢復後，就可以將VIP資源再次搶回來
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
182.148.15.236
}
track_script {
chk_mysql_port
}
}
編寫切換指令碼。KeepAlived做心跳檢測，如果Master的MySQL服務掛了(3306埠掛了),那麼它就會選擇自殺。Slave的KeepAlived通過心跳檢測發現這個情況，就會將VIP的請求接管
[root@master1 ~]# vim /opt/chk_mysql.sh
#!/bin/bash
counter=$(netstat -na|grep "LISTEN"|grep "3306"|wc -l)
if [ "${counter}" -eq 0 ]; then
/etc/init.d/keepalived stop
fi
[root@master1 ~]# chmod 755 /opt/chk_mysql.sh
啟動keepalived服務
[root@master1 ~]# /etc/init.d/keepalived start
正在啟動 keepalived： [確定]
4）master2機器上的keepalived配置。master2機器上的keepalived.conf檔案只修改priority為90、nopreempt不設定、real_server設定本地IP。
[root@master2 ~]# cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bak
[root@master2 ~]# >/etc/keepalived/keepalived.conf
[root@master2 ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
ops@wangshibo.cn
tech@wangshibo.cn
}
notification_email_from ops@wangshibo.cn
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id MASTER-HA
}
vrrp_script chk_mysql_port {
script "/opt/chk_mysql.sh"
interval 2
weight -5
fall 2
rise 1
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
mcast_src_ip 182.148.15.237
virtual_router_id 51
priority 99
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
182.148.15.236
}
track_script {
chk_mysql_port
}
}
[root@master2 ~]# cat /opt/chk_mysql.sh
#!/bin/bash
counter=$(netstat -na|grep "LISTEN"|grep "3306"|wc -l)
if [ "${counter}" -eq 0 ]; then
/etc/init.d/keepalived stop
fi
[root@master2 ~]# chmod 755 /opt/chk_mysql.sh
[root@master2 ~]# /etc/init.d/keepalived start
正在啟動 keepalived： [確定]
5）master1和master2兩臺伺服器都要授權允許root使用者遠端登入，用於在客戶端登陸測試！
mysql> grant all on *.* to root@'%' identified by "1234567";
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)
6）在master1和master2兩臺機器上設定iptables防火牆規則，如下：
[root@master1 ~]# cat /etc/sysconfig/iptables
........
-A INPUT -s 182.148.15.0/24 -d 224.0.0.18 -j ACCEPT #允許組播地址通訊
-A INPUT -s 182.148.15.0/24 -p vrrp -j ACCEPT #允許VRRP（虛擬路由器冗餘協）通訊
-A INPUT -m state --state NEW -m tcp -p tcp --dport 3306 -j ACCEPT #開放mysql的3306埠
[root@master1 ~]# /etc/init.d/iptables restart
三、Mysql＋keepalived故障轉移的高可用測試
1）通過Mysql客戶端通過VIP連線，看是否連線成功。
比如，在遠端一臺測試機上連線，通過vip地址可以正常連線（下面的連線許可權要是在服務端提前授權的）
[root@dev-new-test ~]# mysql -h182.148.15.236 -uroot -p123456
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 60
Server version: 5.6.35-log Source distribution
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> select * from huanqiu.haha;
+----+-----------+
| id | name |
+----+-----------+
| 1 | 王士博 |
| 2 | 郭慧慧 |
| 3 | 周正 |
| 4 | 李敏 |
+----+-----------+
4 rows in set (0.00 sec)
2）預設情況下，vip是在master1上的。使用"ip addr"命令檢視vip切換情況
[root@master1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:3c:25:42 brd ff:ff:ff:ff:ff:ff
inet 182.148.15.238/27 brd 182.148.15.255 scope global eth0
inet 182.148.15.236/32 scope global eth0 //這個32位子網掩碼的vip地址表示該資源目前還在master1機器上
inet 182.148.15.236/27 brd 82.48.115.255 scope global secondary eth0:0
inet6 fe80::5054:ff:fe3c:2542/64 scope link
valid_lft forever preferred_lft forever
停止master1機器上的mysql服務，根據配置中的指令碼，mysql服務停了，keepalived也會停，從而vip資源將會切換到master2機器上。（mysql服務沒有起來的時候，keepalived服務也無法順利啟動！）
[root@master1 ~]# /etc/init.d/mysql stop
Shutting down MySQL.. SUCCESS!
[root@master1 ~]# ps -ef|grep mysql
root 25812 21588 0 17:30 pts/0 00:00:00 grep mysql
[root@master1 ~]# ps -ef|grep keepalived
root 25814 21588 0 17:30 pts/0 00:00:00 grep keepalived
[root@master1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:3c:25:42 brd ff:ff:ff:ff:ff:ff
inet 182.148.15.238/27 brd 182.148.15.255 scope global eth0
inet 182.148.15.236/27 brd 82.48.115.255 scope global secondary eth0:0
inet6 fe80::5054:ff:fe3c:2542/64 scope link
valid_lft forever preferred_lft forever
如上結果，發現32位子網掩碼的vip沒有了，說明此時vip資源已不在master1機器上了
檢視下master1的系統日誌，如下，會發現vip資源已經切換走了
[root@master1 ~]# tail -f /var/log/messages
Apr 15 17:17:43 localhost Keepalived_vrrp[23037]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:17:48 localhost Keepalived_vrrp[23037]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:17:48 localhost Keepalived_vrrp[23037]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on eth0 for 182.148.15.236
Apr 15 17:17:48 localhost Keepalived_vrrp[23037]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:17:48 localhost Keepalived_vrrp[23037]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:17:48 localhost Keepalived_vrrp[23037]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:17:48 localhost Keepalived_vrrp[23037]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:39 localhost Keepalived_healthcheckers[23036]: Stopped
Apr 15 17:30:39 localhost Keepalived_vrrp[23037]: VRRP_Instance(VI_1) sent 0 priority
Apr 15 17:30:39 localhost Keepalived_vrrp[23037]: VRRP_Instance(VI_1) removing protocol VIPs.
再到master2機器上，發現vip資源的確切換過來了
[root@master2 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:95:1f:6d brd ff:ff:ff:ff:ff:ff
inet 182.148.15.237/27 brd 182.148.15.255 scope global eth0
inet 182.148.15.236/32 scope global eth0
inet6 fe80::5054:ff:fe95:1f6d/64 scope link
valid_lft forever preferred_lft forever
檢視master2的系統日誌
[root@master2 ~]# tail -f /var/log/messages
Apr 15 17:30:41 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:41 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:41 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:41 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
3）再次啟動master1的mysql和keepalived服務。（注意：如果restart重啟mysql，那麼還要啟動下keepalived，因為mysql重啟，根據指令碼會造成keepalived關閉）
注意：一定要先啟動mysql服務，然後再啟動keepalived服務。如果先啟動keepalived服務，按照上面的配置，mysql沒有起來，就會自動關閉keepalived。
[root@master1 ~]# /etc/init.d/mysql start
Starting MySQL.. SUCCESS!
[root@master1 ~]# /etc/init.d/keepalived start
正在啟動 keepalived： [確定]
啟動這兩個伺服器後，稍微等過一會兒，注意觀察會發現vip資源再次從master2機器上切換回來了。
[root@master1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:3c:25:42 brd ff:ff:ff:ff:ff:ff
inet 182.148.15.238/27 brd 182.148.15.255 scope global eth0
inet 182.148.15.236/32 scope global eth0
inet 182.148.15.236/27 brd 82.48.115.255 scope global secondary eth0:0
inet6 fe80::5054:ff:fe3c:2542/64 scope link
valid_lft forever preferred_lft forever
[root@master1 ~]# tail -f /var/log/messages
Apr 15 17:40:41 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:41 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:41 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:41 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:46 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:46 localhost Keepalived_vrrp[27002]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on eth0 for 182.148.15.236
Apr 15 17:40:46 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:46 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:46 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:46 localhost Keepalived_vrrp[27002]: Sending gratuitous ARP on eth0 for 182.148.15.236
再看看master2機器，發現vip資源又被恢復後的master1搶過去了
[root@master2 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:95:1f:6d brd ff:ff:ff:ff:ff:ff
inet 182.148.15.237/27 brd 182.148.15.255 scope global eth0
inet6 fe80::5054:ff:fe95:1f6d/64 scope link
valid_lft forever preferred_lft forever
[root@master2 ~]# tail -f /var/log/messages
Apr 15 17:30:41 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:30:46 localhost Keepalived_vrrp[8731]: Sending gratuitous ARP on eth0 for 182.148.15.236
Apr 15 17:40:41 localhost Keepalived_vrrp[8731]: VRRP_Instance(VI_1) Received advert with higher priority 101, ours 99
Apr 15 17:40:41 localhost Keepalived_vrrp[8731]: VRRP_Instance(VI_1) Entering BACKUP STATE
Apr 15 17:40:41 localhost Keepalived_vrrp[8731]: VRRP_Instance(VI_1) removing protocol VIPs.
4）同樣，關閉master1機器的keepalived服務，vip資源會自動切換到master2機器上。當master1的keepalived服務恢復後，會將vip資源再次切回來。
[root@master1 ~]# /etc/init.d/keepalived stop
停止 keepalived： [確定]
[root@master1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:3c:25:42 brd ff:ff:ff:ff:ff:ff
inet 182.148.15.238/27 brd 182.148.15.255 scope global eth0
inet 182.148.15.236/27 brd 82.48.115.255 scope global secondary eth0:0
inet6 fe80::5054:ff:fe3c:2542/64 scope link
valid_lft forever preferred_lft forever
檢視master2，發現vip切過來了
[root@master2 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:95:1f:6d brd ff:ff:ff:ff:ff:ff
inet 182.148.15.237/27 brd 182.148.15.255 scope global eth0
inet 182.148.15.236/32 scope global eth0
inet6 fe80::5054:ff:fe95:1f6d/64 scope link
valid_lft forever preferred_lft forever
再次恢復master1的keepalived服務，發現vip資源很快油切回來了。
[root@master1 ~]# /etc/init.d/keepalived start
正在啟動 keepalived： [確定]
[root@master1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:3c:25:42 brd ff:ff:ff:ff:ff:ff
inet 182.148.15.238/27 brd 182.148.15.255 scope global eth0
inet 182.148.15.236/32 scope global eth0
inet 182.148.15.236/27 brd 82.48.115.255 scope global secondary eth0:0
inet6 fe80::5054:ff:fe3c:2542/64 scope link
valid_lft forever preferred_lft forever
在此檢視master2，發現vip資源被切走了
[root@master2 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 52:54:00:95:1f:6d brd ff:ff:ff:ff:ff:ff
inet 182.148.15.237/27 brd 182.148.15.255 scope global eth0
inet6 fe80::5054:ff:fe95:1f6d/64 scope link
valid_lft forever preferred_lft forever
以上在vip資源切換過程中，對於客戶端連線mysql（使用vip連線）來說幾乎是沒有任何影響的。
------------------------------------溫馨提示（Keepalived的搶佔和非搶佔模式）---------------------------------------
keepalive是基於vrrp協議在linux主機上以守護程式方式，根據配置檔案實現健康檢查。 VRRP是一種選擇協議，它可以把一個虛擬路由器的責任動態分配到區域網上的VRRP路由器中的一臺。 控制虛擬路由器IP地址的VRRP路由器稱為主路由器，它負責轉發資料包到這些虛擬IP地址。 一旦主路由器不可用，這種選擇過程就提供了動態的故障轉移機制，這就允許虛擬路由器的IP地址可以作為終端主機的預設第一跳路由器。 keepalive通過組播，單播等方式（自定義），實現keepalive主備推選。工作模式分為搶佔和非搶佔（通過引數nopreempt來控制）。 1）搶佔模式： 主服務正常工作時，虛擬IP會在主上，備不提供服務，當主服務優先順序低於備的時候，備會自動搶佔虛擬IP，這時，主不提供服務，備提供服務。 也就是說，工作在搶佔模式下，不分主備，只管優先順序。 如上配置，不管keepalived.conf裡的state配置成master還是backup，只看誰的priority優先順序高（一般而言，state為MASTER的優先順序要高於BACKUP）。 priority優先順序高的那一個在故障恢復後，會自動將VIP資源再次搶佔回來！！ 2）非搶佔模式： 這種方式通過引數nopreempt（一般設定在advert_int的那一行下面）來控制。不管priority優先順序，只要MASTER機器發生故障，VIP資源就會被切換到BACKUP上。 並且當MASTER機器恢復後，也不會去將VIP資源搶佔回來，直至BACKUP機器發生故障時，才能自動切換回來。 千萬注意： nopreempt這個引數只能用於state為backup的情況，所以在配置的時候要把master和backup的state都設定成backup，這樣才會實現keepalived的非搶佔模式！ 也就是說： a）當state狀態一個為master，一個為backup的時候，加不加nopreempt這個引數都是一樣的效果。即都是根據priority優先順序來決定誰搶佔vip資源的，是搶佔模式！ b）當state狀態都設定成backup，如果不配置nopreempt引數，那麼也是看priority優先順序決定誰搶佔vip資源，即也是搶佔模式。 c）當state狀態都設定成backup，如果配置nopreempt引數，那麼就不會去考慮priority優先順序了，是非搶佔模式！即只有vip當前所在機器發生故障，另一臺機器才能接管vip。即使優先順序高的那一臺機器恢復 後也不會主動搶回vip，只能等到對方發生故障，才會將vip切回來。
---------------------------------mysql狀態檢測指令碼優化---------------------------------
上面的mysql監測指令碼有點過於簡單且粗暴，即指令碼一旦監測到Master的mysql服務關閉，就立刻把keepalived服務關閉，從而實現vip轉移！
下面對該指令碼進行優化，優化後，當監測到Master的mysql服務關閉後，就會將vip切換到Backup上（但此時Master的keepalived服務不會被暴力kill）
當Master的mysql服務恢復後，就會再次將VIP資源切回來！
[root@master ~]# cat /opt/chk_mysql.sh
#!/bin/bash
MYSQL=/usr/local/mysql/bin/mysql
MYSQL_HOST=localhost
MYSQL_USER=root
MYSQL_PASSWORD=123456
CHECK_TIME=3
#mysql is working MYSQL_OK is 1 , mysql down MYSQL_OK is 0
MYSQL_OK=1
function check_mysql_helth (){
$MYSQL -h $MYSQL_HOST -u $MYSQL_USER -p${MYSQL_PASSWORD} -e "show status;" >/dev/null 2>&1
if [ $? = 0 ] ;then
MYSQL_OK=1
else
MYSQL_OK=0
fi
return $MYSQL_OK
}
while [ $CHECK_TIME -ne 0 ]
do
let "CHECK_TIME -= 1"
check_mysql_helth
if [ $MYSQL_OK = 1 ] ; then
CHECK_TIME=0
exit 0
fi
if [ $MYSQL_OK -eq 0 ] && [ $CHECK_TIME -eq 0 ]
then
pkill keepalived
exit 1
fi
sleep 1
done