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MySQL双机高可用的负载均衡(读写分离、主从自动切换)架构设计

架构简介

 

前几天网友来信说帮忙实现这样一个架构:只有两台机器,需要实现其中一台死机之后另一台能接管这台机器的服务,并且在两台机器正常服务时,两台机器都能用上。于是设计了如下的架构。

双机ha架构图 此架构主要是由keepalived实现双机高可用,维护了一个外网VIP,一个内网VIP。正常情况时,外网VIP和内网VIP都绑定在server1服务器,web请求发送到server1的nginx,nginx对于静态资源请求就直接在本机检索并返回,对于php的动态请求,则负载均衡到server1和server2。对于SQL请求,会将此类请求发送到Atlas MySQL中间件,Atlas接收到请求之后,把涉及写操作的请求发送到内网VIP,读请求操作发送到mysql从,这样就实现了读写分离。

 

当主服务器server1宕机时,keepalived检测到后,立即把外网VIP和内网VIP绑定到server2,并把server2的mysql切换成主库。此时由于外网VIP已经转移到了server2,web请求将发送给server2的nginx。nginx检测到server1宕机,不再把请求转发到server1的php-fpm。之后的sql请求照常发送给本地的atlas,atlas把写操作发送给内网VIP,读操作发送给mysql从,由于内网VIP已经绑定到server2了,server2的mysql同时接受写操作和读操作。

 

当主服务器server1恢复后,server1的mysql自动设置为从,与server2的mysql主同步。keepalived不抢占server2的VIP,继续正常服务。

 

架构要求

 

要实现此架构,需要三个条件:

1、服务器可以设置内网IP,并且设置的内网IP互通;

2、服务器可以随意绑定IDC分配给我们使用的外网IP,即外网IP没有绑定MAC地址;

3、MySQL服务器支持GTID,即MySQL-5.6.5以上版本。

 

环境说明

 

server1

eth0: 10.96.153.110(对外IP)

eth1: 192.168.1.100(对内IP)

server2

eth0: 10.96.153.114(对外IP)

eth1: 192.168.1.101(对内IP)

系统都是CentOS-6。

 

对外VIP: 10.96.153.239

对内VIP: 192.168.1.150

 

hosts设置

 

/etc/hosts:

192.168.1.100 server1

192.168.1.101 server2

 

Nginx PHP MySQL Memcached安装

 

这几个软件的安装推荐使用EZHTTP来完成。

 

解决session共享问题

 

php默认的session存储是在/tmp目录下,现在我们是用两台服务器作php请求的负载,这样会造成session分布在两台服务器的/tmp目录下,导致依赖于session的功能不正常。我们可以使用memcached来解决此问题。

上一步我们已经安装好了memcached,现在只需要配置php.ini来使用memcached,配置如下,打开php.ini配置文件,修改为如下两行的值:

session.save_handler = memcache

session.save_path = "tcp://192.168.1.100:11211,tcp://192.168.1.101:11211"

之后重启php-fpm生效。

 

Nginx配置

 

Server1配置

http {

[...]

    upstream php-server {

           server 192.168.1.101:9000;

           server 127.0.0.1:9000;

           keepalive 100;

    }

[...]

 server {

    [...]

        location ~ \.php$ {

                        fastcgi_pass   php-server;

                        fastcgi_index  index.php;

                        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;

                        include        fastcgi_params;

        }

    [...]

 }

[...]

}

 

Server2配置

http {

[...]

    upstream php-server {

           server 192.168.1.100:9000;

           server 127.0.0.1:9000;

           keepalive 100;

    }

[...]

 server {

    [...]

        location ~ \.php$ {

                        fastcgi_pass   php-server;

                        fastcgi_index  index.php;

                        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;

                        include        fastcgi_params;

        }

    [...]

 }

[...]

}

这两个配置主要的作用是设置php请求的负载均衡。

 

MySQL配置

 

mysql util安装

我们需要安装mysql util里的主从配置工具来实现主从切换。

cd /tmp

wget http://dev.mysql.com/get/Downloads/MySQLGUITools/mysql-utilities-1.5.3.tar.gz

tar xzf mysql-utilities-1.5.3.tar.gz

cd mysql-utilities-1.5.3

python setup.py build

python setup.py install

 

mysql my.cnf配置

server1:

[mysql]

[...]

protocol=tcp

[...]

[...]

[mysqld]

[...]

# BINARY LOGGING #

log-bin = /usr/local/mysql/data/mysql-bin

expire-logs-days = 14

binlog-format= row

log-slave-updates=true

gtid-mode=on

enforce-gtid-consistency =true

master-info-repository=TABLE

relay-log-info-repository=TABLE

server-id=1

report-host=server1

report-port=3306

[...]

server2:

[mysql]

[...]

protocol=tcp

[...]

[mysqld]

[...]

# BINARY LOGGING #

log-bin = /usr/local/mysql/data/mysql-bin

expire-logs-days = 14

binlog-format= row

log-slave-updates=true

gtid-mode=on

enforce-gtid-consistency =true

master-info-repository=TABLE

relay-log-info-repository=TABLE

server-id=2

report-host=server2

report-port=3306

[...]

这两个配置主要是设置了binlog和启用gtid-mode,并且需要设置不同的server-id和report-host。

 

开放root帐号远程权限

我们需要在两台mysql服务器设置root帐号远程访问权限。

mysql> grant all on *.* to 'root'@'192.168.1.%' identified by 'Xp29at5F37' with grant option;

mysql> grant all on *.* to 'root'@'server1' identified by 'Xp29at5F37' with grant option;

mysql> grant all on *.* to 'root'@'server2' identified by 'Xp29at5F37' with grant option;

mysql> flush privileges;

 

设置mysql主从

在任意一台执行如下命令:

mysqlreplicate --master=root:Xp29at5F37@server1:3306 --slave=root:Xp29at5F37@server2:3306 --rpl-user=rpl:o67DhtaW

# master on server1: … connected.

# slave on server2: … connected.

# Checking for binary logging on master…

# Setting up replication…

# …done.

 

显示主从关系

mysqlrplshow --master=root:Xp29at5F37@server1 --discover-slaves-login=root:Xp29at5F37

# master on server1: … connected.

# Finding slaves for master: server1:3306

# Replication Topology Graph

server1:3306 (MASTER)

|

— server2:3306 – (SLAVE)

 

检查主从状态

mysqlrplcheck --master=root:Xp29at5F37@server1 --slave=root:Xp29at5F37@server2

# master on server1: … connected.

# slave on server2: … connected.

Test Description Status

—————————————————————————

Checking for binary logging on master [pass]

Are there binlog exceptions? [pass]

Replication user exists? [pass]

Checking server_id values [pass]

Checking server_uuid values [pass]

Is slave connected to master? [pass]

Check master information file [pass]

Checking InnoDB compatibility [pass]

Checking storage engines compatibility [pass]

Checking lower_case_table_names settings [pass]

Checking slave delay (seconds behind master) [pass]

# …done.

 

Keepalived配置

 

keepalived安装(两台都装)

yum -y install keepalived

chkconfig keepalived on

 

keepalived配置(server1)

vi /etc/keepalived/keepalived.conf

vrrp_sync_group VG_1 {

group {

inside_network

outside_network

}

}

 

vrrp_instance inside_network {

state BACKUP

interface eth1

virtual_router_id 51

priority 101

advert_int 1

authentication {

auth_type PASS

auth_pass 3489

}

virtual_ipaddress {

192.168.1.150/24

}

nopreempt

notify /data/sh/mysqlfailover-server1.sh

}

 

vrrp_instance outside_network {

state BACKUP

interface eth0

virtual_router_id 50

priority 101

advert_int 1

authentication {

auth_type PASS

auth_pass 3489

}

virtual_ipaddress {

10.96.153.239/24

}

nopreempt

}

 

keepalived配置(server2)

vrrp_sync_group VG_1 {

group {

inside_network

outside_network

}

}

 

vrrp_instance inside_network {

state BACKUP

interface eth1

virtual_router_id 51

priority 100

advert_int 1

authentication {

auth_type PASS

auth_pass 3489

}

virtual_ipaddress {

192.168.1.150

}

notify /data/sh/mysqlfailover-server2.sh

}

 

vrrp_instance outside_network {

state BACKUP

interface eth0

virtual_router_id 50

priority 100

advert_int 1

authentication {

auth_type PASS

auth_pass 3489

}

virtual_ipaddress {

10.96.153.239/24

}

}

此keepalived配置需要注意的是:

1、两台server的state都设置为backup,server1增加nopreempt配置,并且server1 priority比server2高,这样用来实现当server1从宕机恢复时,不抢占VIP;

2、server1设置notify /data/sh/mysqlfailover-server1.sh,server2设置notify /data/sh/mysqlfailover-server2.sh,作用是自动切换主从

/data/sh/mysqlfailover-server1.sh脚本内容:

#!/bin/bash

 

sleep 10

state=$3

result=`mysql -h127.0.0.1 -P3308 -uroot -pXp29at5F37 -e 'show slave status;'`

[[ "$result" == "" ]] && mysqlState="master" || mysqlState="slave"

 

if [[ "$state" == "MASTER" ]];then

if [[ "$mysqlState" == "slave" ]];then

mysqlrpladmin --slave=root:Xp29at5F37@server1:3308 failover

fi

 

elif [[ "$state" == "BACKUP" ]];then

if [[ "$mysqlState" == "master" ]];then

mysqlreplicate --master=root:Xp29at5F37@server2:3308 --slave=root:Xp29at5F37@server1:3308 --rpl-user=rpl:o67DhtaW

fi

fi

 

sed -i 's/proxy-read-only-backend-addresses.*/proxy-read-only-backend-addresses = 192.168.1.150:3308/' /usr/local/mysql-proxy/conf/my.cnf

mysql -h127.0.0.1 -P2345 -uuser -ppwd -e "REMOVE BACKEND 2;"

/data/sh/mysqlfailover-server2.sh脚本内容:

#!/bin/bash

 

sleep 10

state=$3

result=`mysql -h127.0.0.1 -P3308 -uroot -pXp29at5F37 -e 'show slave status;'`

[[ "$result" == "" ]] && mysqlState="master" || mysqlState="slave"

 

if [[ "$state" == "MASTER" ]];then

if [[ "$mysqlState" == "slave" ]];then

mysqlrpladmin --slave=root:Xp29at5F37@server2:3308 failover

fi

 

elif [[ "$state" == "BACKUP" ]];then

if [[ "$mysqlState" == "master" ]];then

mysqlreplicate --master=root:Xp29at5F37@server1:3308 --slave=root:Xp29at5F37@server2:3308 --rpl-user=rpl:o67DhtaW

fi

fi

 

sed -i 's/proxy-read-only-backend-addresses.*/proxy-read-only-backend-addresses = 192.168.1.150:3308/' /usr/local/mysql-proxy/conf/my.cnf

mysql -h127.0.0.1 -P2345 -uuser -ppwd -e "REMOVE BACKEND 2;"

 

Atlas设置

 

atlas安装

到这里下载最新版本,https://github.com/Qihoo360/Atlas/releases

cd /tmp

wget https://github.com/Qihoo360/Atlas/releases/download/2.2.1/Atlas-2.2.1.el6.x86_64.rpm

rpm -i Atlas-2.2.1.el6.x86_64.rpm

 

atlas配置

cd /usr/local/mysql-proxy/conf

cp test.cnf my.cnf

vi my.cnf

调整如下参数,

proxy-backend-addresses = 192.168.1.150:3306

proxy-read-only-backend-addresses = 192.168.1.101:3306

pwds = root:qtyU1btXOo074Itvx0UR9Q==

event-threads = 8

注意:

proxy-backend-addresse设置为内网VIP

proxy-read-only-backend-addresses设置为server2的IP

root:qtyU1btXOo074Itvx0UR9Q==设置数据库的用户和密码,密码是通过/usr/local/mysql-proxy/bin/encrypt Xp29at5F37生成。

更详细参数解释请查看,Atlas配置详解。

 

启动atlas

/usr/local/mysql-proxy/bin/mysql-proxy --defaults-file=/usr/local/mysql-proxy/conf/my.cnf

之后程序里配置mysql就配置127.0.0.1:1234就好。

 

部署atlas自动维护脚本

在两台机器都部署此脚本,并添加定时任务(如每2分钟运行一次)我们把脚本放在/data/sh/auto_maintain_atlas.sh,脚本内容为:

#!/bin/bash

 

count=`mysql -N -h127.0.0.1 -P2345 -uuser -ppwd -e "select * from backends;" | wc -l`

 

if [[ "$count" == "1" ]];then

result=`mysql -hserver1 -P3308 -uroot -pXp29at5F37 -e 'show slave status\G'`

if echo "$result" | grep Slave_IO_State;then

slaveIP=192.168.1.100

else

result=`mysql -hserver2 -P3308 -uroot -pXp29at5F37 -e 'show slave status\G'`

slaveIP=192.168.1.101

fi

 

        slaveIORunning=`echo "$result" | awk -F':' '/Slave_IO_Running:/{print $2}'`

        slaveSQLRunning=`echo "$result" | awk -F':' '/Slave_SQL_Running:/{print $2}'`

        SlaveSQLRunning_State=`echo "$result" | awk -F':' '/Slave_SQL_Running_State:/{print $2}'`

if [[ "$slaveIORunning" =~ "Yes" && "$slaveSQLRunning" =~ "Yes" && "$SlaveSQLRunning_State" =~ "Slave has read all relay log" ]];then

mysql -h127.0.0.1 -P2345 -uuser -ppwd -e "add slave ${slaveIP}:3308;"

fi

fi

为什么需要这个脚本呢?假设目前mysql主服务器在s1,s1宕机后,s2接管VIP,接着删除atlas中设置的slave backend,其mysql提升为主。过一段时间后,s1从宕机中恢复,这时候s1的mysql自动切换为从,接着删除atlas中设置的slave backend,开始连接s2的mysql主同步数据。到这个时候我们发现,已经不存在读写分离了,所有的sql都发送给了s2的mysql。auto_maintain_atlas.sh脚本就派上用场了,此脚本会定时的检查主从是否已经同步完成,如果完成就自动增加slave backend,这样读写分离又恢复了,完全不需要人工干预。

 

server1主宕机测试

 

测试keepalived是否工作正常

我们来模拟server1宕机。

在server1上执行shutdown关机命令。

此时我们登录server2,执行ip addr命令,输出如下:

1: lo: mtu 16436 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: mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:81:9d:42 brd ff:ff:ff:ff:ff:ff

inet 10.96.153.114/24 brd 10.96.153.255 scope global eth0

inet 10.96.153.239/24 scope global secondary eth0

inet6 fe80::20c:29ff:fe81:9d42/64 scope link

valid_lft forever preferred_lft forever

3: eth1: mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:81:9d:4c brd ff:ff:ff:ff:ff:ff

inet 192.168.1.101/24 brd 192.168.1.255 scope global eth1

inet 192.168.1.150/32 scope global eth1

inet6 fe80::20c:29ff:fe81:9d4c/64 scope link

valid_lft forever preferred_lft forever

我们看到对外VIP 10.96.153.239和对内IP 192.168.1.150已经转移到server2了,证明keepalived运行正常。

 

测试是否自动切换了主从

登录server2的mysql服务器,执行show slave status;命令,如下:

mysql> show slave status\G

Empty set (0.00 sec)

我们发现从状态已经为空,证明已经切换为主了。

 

测试server1是否抢占VIP

为什么要测试这个呢?如果server1恢复之后抢占了VIP,而我们的Atlas里后端设置的是VIP,这样server1启动之后,sql的写操作就会向server1的mysql发送,而server1的mysql数据是旧于server2的,所以这样会造成数据不一致,这个是非常重要的测试。

我们先来启动server1,之后执行ip addr,输出如下:

1: lo: mtu 16436 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: mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:f1:4f:4e brd ff:ff:ff:ff:ff:ff

inet 10.96.153.110/24 brd 10.96.153.255 scope global eth0

inet6 fe80::20c:29ff:fef1:4f4e/64 scope link

valid_lft forever preferred_lft forever

3: eth1: mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:f1:4f:58 brd ff:ff:ff:ff:ff:ff

inet 192.168.1.100/24 brd 192.168.1.255 scope global eth1

inet6 fe80::20c:29ff:fef1:4f58/64 scope link

valid_lft forever preferred_lft forever

我们看到,server1并没有抢占VIP,测试正常。不过另人郁闷的是,在虚拟机的环境并没有测试成功,不知道为什么。

 

测试server2的atlas是否已经删除slave backend

我们测试这个是为了保证atlas已经没有slave backend,也就是没有从库的设置了,否则当server1恢复时,有可能会把读请求发送给server1的mysql,造成读取了旧数据的问题。


[root@server1 ~]# mysql -h127.0.0.1 -P2345 -uuser -ppwd

mysql> select * from backends;

————- ——————– ——- —— 

| backend_ndx | address | state | type |

————- ——————– ——- —— 

| 1 | 192.168.1.150:3308 | up | rw |

————- ——————– ——- —— 

1 rows in set (0.00 sec)

如果看到只有一个后端,证明运作正常。

 

测试server1 mysql是否设置为从

serve1恢复后,登录server1的mysql服务器,执行show slave status;命令,如下:


mysql> show slave status\G

*************************** 1. row ***************************

Slave_IO_State: Opening tables

Master_Host: server1

Master_User: rpl

Master_Port: 3308

Connect_Retry: 60

Master_Log_File: mysql-bin.000015

Read_Master_Log_Pos: 48405991

Relay_Log_File: mysql-relay-bin.000002

Relay_Log_Pos: 361

Relay_Master_Log_File: mysql-bin.000015

Slave_IO_Running: Yes

Slave_SQL_Running: yes

 

测试是否自动恢复读写分离

server1恢复后一段时间,我们可以看是读写分离是否已经恢复。


[root@server1 ~]# mysql -h127.0.0.1 -P2345 -uuser -ppwd

Warning: Using a password on the command line interface can be insecure.

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 1

Server version: 5.0.99-agent-admin

Copyright (c) 2000, 2014, 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 backends;

————- ——————– ——- —— 

| backend_ndx | address | state | type |

————- ——————– ——- —— 

| 1 | 192.168.1.150:3308 | up | rw |

| 2 | 192.168.1.100:3308 | up | ro |

————- ——————– ——- —— 

2 rows in set (0.00 sec)


我们看到server1已经被添加为slave backend了。这表示已经成功恢复读写分离。


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