双机高可用、负载均衡、MySQL (读写分离、主从自动切换)架构设计

双机高可用、负载均衡、MySQL (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。

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)

1. yum -y install keepalived
2. 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)

rrp_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 -P3306 -uroot -pXp29at5F37 -e 'show slave status;'`

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

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

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

mysqlrpladmin --slave=root:Xp29at5F37@server1:3306 failover

fi

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

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

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

fi

fi

sed -i 's/proxy-read-only-backend-addresses.*/proxy-read-only-backend-addresses = 192.168.1.150:3306/' /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 -P3306 -uroot -pXp29at5F37 -e 'show slave status;'`

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

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

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

mysqlrpladmin --slave=root:Xp29at5F37@server2:3306 failover

fi

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

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

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

fi

fi

sed -i 's/proxy-read-only-backend-addresses.*/proxy-read-only-backend-addresses = 192.168.1.150:3306/' /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 -P3306 -uroot -pXp29at5F37 -e 'show slave status\G'`

if echo "$result" | grep Slave_IO_State;then

slaveIP=192.168.1.100

else

result=`mysql -hserver2 -P3306 -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}:3306;"

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 statusG

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 | 192.168.1.150:3306 | 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 statusG

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

Slave_IO_State: Opening tables

Master_Host: server1

Master_User: rpl

Master_Port: 3306

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 | 192.168.1.150:3306 | up | rw |

| 2 | 192.168.1.100:3306 | 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。