共计 11082 个字符，预计需要花费 28 分钟才能阅读完成。
双主 + keepalived 是一个比较简单的 MySQL 高可用架构，适用于中小 MySQL 集群，今天就说说怎么用 keepalived 做 MySQL 的高可用。
1 概述
1.1 keepalived 简介
简单地说，keepalived 就是通过管理 VIP 来实现机器的高可用的，在使用 keepalived 的情况下，只有一台服务器能够提供服务 (通过 VIP 来实现)，当 Master 主机宕机后，VIP 会自动飘移到另一台服务器
keepalived 采用 Master/Slave 模式, 在 Master 上设置配置文件的 VIP，当 Master 宕机后，VIP 自动漂移到另一台 keepalived 服务器上
keepalived 可以用来做各种软件的高可用集群，它会一直检测服务器的状态，如果有一台服务器宕机，或工作出现故障，keepalived 将检测到，并将有故障的服务器从系统中剔除，同时使用其他服务器代替该服务器的工作，当服务器工作正常后 keepalived 自动将服务器加入到服务器群中。
1.2 keepalived 配合双主
keepalived 使用默认配置只能做到主机级别的高可用，但是我们的 MySQL 要做高可用至少要增加以下功能
能够检测 MySQL 服务状态
主节点 read_only=0，备节点 read_only=1
切换时，备节点要等待主节点同步完成
所以，keepalived 实现 MySQL 高可用需要使用自定义脚本来进行扩展
2 环境准备
2.1 数据库环境
操作前已经准备好了一套主主架构数据库，搭建方法参考 MySQL 集群搭建 (2)- 主主从模式
节点信息
IP
系统
端口
MySQL 版本
节点
读写
说明
10.0.0.247
Centos6.5
3306
5.7.9
Master
读写
主节点
10.0.0.248
Centos6.5
3306
5.7.9
Standby
只读, 可切换为读写
备主节点
VIP 信息
简称
VIP
类型
RW-VIP
10.0.0.237
读写 VIP
Master 参考配置
[client]
port = 3306
default-character-set=utf8mb4
socket = /data/mysql_db/test_db/mysql.sock
[mysqld]
datadir = /data/mysql_db/test_db
basedir = /usr/local/mysql57
tmpdir = /tmp
socket = /data/mysql_db/test_db/mysql.sock
pid-file = /data/mysql_db/test_db/mysql.pid
skip-external-locking = 1
skip-name-resolve = 1
port = 3306
server_id = 2473306
default-storage-engine = InnoDB
character-set-server = utf8mb4
default_password_lifetime=0
auto_increment_offset = 1
auto_increment_increment = 2
#### log ####
log_timestamps=system
log_bin = /data/mysql_log/test_db/mysql-bin
log_bin_index = /data/mysql_log/test_db/mysql-bin.index
binlog_format = row
relay_log_recovery=ON
relay_log=/data/mysql_log/test_db/mysql-relay-bin
relay_log_index=/data/mysql_log/test_db/mysql-relay-bin.index
log_error = /data/mysql_log/test_db/mysql-error.log
#### replication ####
log_slave_updates = 1
replicate_wild_ignore_table = information_schema.%,performance_schema.%,sys.%
#### semi sync replication settings #####
plugin_dir=/usr/local/mysql57/lib/plugin
plugin_load = “rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so”
loose_rpl_semi_sync_master_enabled = 1
loose_rpl_semi_sync_slave_enabled = 1
Slave 参考配置
[client]
port = 3306
default-character-set=utf8mb4
socket = /data/mysql_db/test_db/mysql.sock
[mysqld]
datadir = /data/mysql_db/test_db
basedir = /usr/local/mysql57
tmpdir = /tmp
socket = /data/mysql_db/test_db/mysql.sock
pid-file = /data/mysql_db/test_db/mysql.pid
skip-external-locking = 1
skip-name-resolve = 1
port = 3306
server_id = 2483306
default-storage-engine = InnoDB
character-set-server = utf8mb4
default_password_lifetime=0
auto_increment_offset = 2
auto_increment_increment = 2
#### log ####
log_timestamps=system
log_bin = /data/mysql_log/test_db/mysql-bin
log_bin_index = /data/mysql_log/test_db/mysql-bin.index
binlog_format = row
relay_log_recovery=ON
relay_log=/data/mysql_log/test_db/mysql-relay-bin
relay_log_index=/data/mysql_log/test_db/mysql-relay-bin.index
log_error = /data/mysql_log/test_db/mysql-error.log
#### replication ####
log_slave_updates = 1
replicate_wild_ignore_table = information_schema.%,performance_schema.%,sys.%
#### semi sync replication settings #####
plugin_dir=/usr/local/mysql57/lib/plugin
plugin_load = “rpl_semi_sync_master=semisync_master.so;rpl_semi_sync_slave=semisync_slave.so”
loose_rpl_semi_sync_master_enabled = 1
loose_rpl_semi_sync_slave_enabled = 1
2.2 创建监控用的账号
– 由于是测试环境，账号密码设置比较随便
create user monitor@’localhost’ identified by ‘monitor’;
grant all on *.* to monitor@’localhost’;
flush privileges;
2.3 安装 keepalived
我们在 Master 和 Slave 上部署 keepalived
1). yum 安装
如果有对应的 yum 源，直接安装就可以了
yum install -y keepalived
2). 源码安装
下载安装包, 下载地址 keepalived, 使用 1.2.24 版本举例
# 安装依赖
yum install -y gcc popt-devel openssl openssl-devel libssl-dev libnl-devel popt-devel libnfnetlink-devel
# 下载包
wget http://www.keepalived.org/software/keepalived-1.2.24.tar.gz
# 解压安装
tar -xvz -f keepalived-1.2.24.tar.gz
cd keepalived-1.2.24
./configure –prefix=/usr/local/keepalived
make && make install
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
mkdir /etc/keepalived/
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
3 配置高可用
3.1 keepalived 配置
打开 /etc/keepalived/keepalived.conf 文件, 按照实际情况加上下面的配置
global_defs {
router_id MYSQL_MM # 标识
vrrp_skip_check_adv_addr
vrrp_strict # 严格执行 VRRP 协议规范
vrrp_garp_interval 0
vrrp_gna_interval 0
}
vrrp_script check_mysql {
script “/bin/sh /etc/keepalived/keepalived_mysql_check.sh” # 检查脚本
interval 10 # 检查周期
}
vrrp_instance MYSQL_MM {
state BACKUP # 都设为 BACKUP，避免起来后抢占
interface eth0 # 网卡名称，根据实际情况填写
virtual_router_id 243 # 用来区分 VRRP 组播的标记，取值 0-255
priority 100
advert_int 1
nopreempt # 设为非抢占
authentication {
auth_type PASS
auth_pass 1111
}
# Master 节点可以注释掉下面语句，防止启动 keepalived 的时候执行脚本
notify_master “/bin/sh /etc/keepalived/keepalived_mysql_start.sh” # 变为 MASTER 时执行
virtual_ipaddress {
10.0.0.237
}
# Slave 节点可以注释下面检查脚本，Slave 没有必要一直检查
track_script {
check_mysql
}
}
3.2 配置检查脚本
打开 /etc/keepalived/keepalived_mysql_check.sh，写入检测脚本
#!/bin/sh
# @Author: chengqm
# MySQL 检测脚本
MyPath=$(cd $(dirname $0); pwd)
cd $MyPath
ThisTime=`date ‘+%F %T’`
log_file=’/var/log/keepalived_mysql.log’
# MySQL 连接方式，根据实际情况调整
export MYSQL_PWD=’monitor’
MYSQL_USER=’monitor’
MYSQL_SOCKET=”/data/mysql_db/test_db/mysql.sock”
mysql_connect=”mysql -u${MYSQL_USER} -S${MYSQL_SOCKET} ”
# 美化输出
function techo() {
message=$1
message_level=$2
if [-e $message_level];then
message_level=’info’
fi
echo “`date ‘+%F %T’` – [${message_level}] $message” >> $log_file
}
# 检查函数, 正常返回 0
function check {
ret=`$mysql_connect -N -e ‘select 1 as value’`
if [$? -ne 0] || [$ret -ne ‘1’];then
return 1
else
return 0
fi
}
function read_only {
param=$1
$mysql_connect -e “set global read_only = ${param}”
techo “ 设置是否只读 read_only ${param}”
}
# 失效转移
function failover {
techo “ 开始执行失效转移 ”
# 1. 停止 keepalived
killall keepalived
# 2. 如果还能执行的话，设为 read_only
read_only 1
if [$? -eq 0];then
# 3. 如果还能执行，kill 所有的连接
$mysql_connect -e “select concat(‘KILL ‘,id,’;’) from information_schema.processlist where user!=’root’ AND db is not null into outfile ‘/tmp/kill.txt.${ThisTime}’;”
if [$? -eq 0];then
$mysql_connect -e “source /tmp/kill.txt.${ThisTime};”
fi
fi
# 4. 其他操作，比如说自动关机
techo “ 失效转移执行成功，当前数据库关闭访问 ”
}
# 有问题检查 4 次
for ((i=1; i<=4; i ++))
do
check
if [$? -eq 0];then
techo “MySQL is ok”
# 正常退出脚本
exit 0
else
techo “Connection failed $i time(s)”
sleep 1
fi
done
techo ‘ 无法连接当前数据库 ’
# 失效转移
failover
注意：脚本没有经过严格测试，需要根据实际情况调整
3.3 配置提升为 Master 时执行的脚本
打开 /bin/sh /etc/keepalived/keepalived_mysql_start.sh”, 写入脚本内容
#!/bin/sh
# @Author: chengqm
# keepalived 变为 Master 时执行
MyPath=$(cd $(dirname $0); pwd)
cd $MyPath
ThisTime=`date ‘+%F %T’`
log_file=’/var/log/keepalived_mysql.log’
# MySQL 连接方式，根据实际情况调整
export MYSQL_PWD=’monitor’
MYSQL_USER=’monitor’
MYSQL_SOCKET=”/data/mysql_db/test_db/mysql.sock”
mysql_connect=”mysql -u${MYSQL_USER} -S${MYSQL_SOCKET} ”
# 美化输出
function techo() {
message=$1
message_level=$2
if [-e $message_level];then
message_level=’info’
fi
echo “`date ‘+%F %T’` – [${message_level}] $message” >> $log_file
}
# 检查函数, 正常返回 0
function check {
ret=`$mysql_connect -N -e ‘select 1 as value’`
if [$? -ne 0] || [$ret -ne ‘1’];then
return 1
else
return 0
fi
}
# 获取 slave status 的信息
function slave_info() {
tmp_file=/tmp/slave_info.tmp
$mysql_connect -e ‘show slave status\G’ > /tmp/slave_info.tmp
slave_sql=`grep ‘Slave_SQL_Running:’ $tmp_file | sed ‘s/\s*//g’ | tr “A-Z” “a-z” | awk -F”:” ‘{print $2}’`
seconds_behind_master=`grep ‘Seconds_Behind_Master:’ $tmp_file | sed ‘s/\s*//g’ | tr “A-Z” “a-z” | awk -F”:” ‘{print $2}’`
master_log_file=`grep ‘Master_Log_File:’ $tmp_file | head -1 | sed ‘s/\s*//g’ | tr “A-Z” “a-z” | awk -F”:” ‘{print $2}’`
master_log_pos=`grep ‘Read_Master_Log_Pos:’ $tmp_file | sed ‘s/\s*//g’ | tr “A-Z” “a-z” | awk -F”:” ‘{print $2}’`
relay_master_log_file=`grep ‘Relay_Master_Log_File:’ $tmp_file | sed ‘s/\s*//g’ | tr “A-Z” “a-z” | awk -F”:” ‘{print $2}’`
exec_master_log_pos=`grep ‘Exec_Master_Log_Pos:’ $tmp_file | sed ‘s/\s*//g’ | tr “A-Z” “a-z” | awk -F”:” ‘{print $2}’`
}
# 设置是否可读
function read_only {
param=$1
$mysql_connect -e “set global read_only = ${param}”
techo “ 设置是否只读 read_only ${param}”
}
# 处理数据同步
function sync_master_log() {
# 如果是数据一致性优先，等待同步完毕。如果是服务可用性优先，可以注销下面的代码
slave_info
if [$slave_sql == “yes”];then
techo “ 当前同步位置 Master ${master_log_file} ${master_log_pos}”
techo “ 等待同步到 Master ${master_log_file} ${master_log_pos}”
$mysql_connect -e “select master_pos_wait(‘$master_log_file’, $master_log_pos);” > /dev/null
techo “ 同步完毕 ”
fi
}
techo “ 当前数据库提升为主库 ”
check
if [$? -ne 0];then
techo “ 无法连接当前数据库 ”
exit 1
fi
# 等待同步
sync_master_log
# 设为可写
read_only 0
注意：脚本没有经过严格测试，需要根据实际情况调整
3.4 启动 keepalived
由于配置了 BACKUP 模式，所以两个 keepalived 先起来的是主，先后在主备节点执行
/etc/init.d/keepalived start
检查 /var/log/message 日志，确认 keepalived 没有报错
检查 Master IP 状态, 确认设置了 VIP
[root@cluster01 shell]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> 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: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether fa:16:3e:de:80:33 brd ff:ff:ff:ff:ff:ff
inet 10.0.0.247/16 brd 10.0.255.255 scope global eth0
inet 10.0.0.237/32 scope global eth0
inet6 fe80::f816:3eff:fede:8033/64 scope link
valid_lft forever preferred_lft forever
检查 MySQL 检测脚本执行情况，确认正常运行
[root@cluster01 ~]# tail -f /var/log/keepalived_mysql.log
…
2019-01-28 15:04:18 – [info] MySQL is ok
2019-01-28 15:04:28 – [info] MySQL is ok
4 失效转移测试
在 mytest 库里新建 nowdate 测试表，只有 id 和 ctime 字段，然后每秒插入一条数据
[root@cluster03 ~]# while true; do date;mysql -h10.0.0.237 -P3306 -umytest -e ‘use mytest;insert into nowdate values (null, now());’; sleep 1;done
Mon Jan 28 15:04:26 CST 2019
Mon Jan 28 15:04:27 CST 2019
…
kill 掉 Master 进程
killall mysqld
查看旧 Master 日志
2019-01-28 15:04:48 – [info] MySQL is ok
2019-01-28 15:04:58 – [info] Connection failed 1 time(s)
2019-01-28 15:04:59 – [info] Connection failed 2 time(s)
2019-01-28 15:05:00 – [info] Connection failed 3 time(s)
2019-01-28 15:05:01 – [info] Connection failed 4 time(s)
2019-01-28 15:05:02 – [info] 无法连接当前数据库
2019-01-28 15:05:02 – [info] 开始执行失效转移
2019-01-28 15:05:02 – [info] 设置是否只读 read_only 1
2019-01-28 15:05:02 – [info] 失效转移执行成功，当前数据库关闭访问
查看新 Master 日志
2019-01-28 15:05:04 – [info] 当前数据库提升为主库
2019-01-28 15:05:04 – [info] 当前同步位置 Master mysql-bin.000015 32338
2019-01-28 15:05:04 – [info] 等待同步到 Master mysql-bin.000015 32338
2019-01-28 15:05:04 – [info] 同步完毕
2019-01-28 15:05:04 – [info] 设置是否只读 read_only 0
2019-01-28 15:05:05 – [info] MySQL is ok
查看新 Master IP，确认 VIP 已经飘过来了
[root@cluster02 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> 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: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether fa:16:3e:66:7e:e8 brd ff:ff:ff:ff:ff:ff
inet 10.0.0.248/16 brd 10.0.255.255 scope global eth0
inet 10.0.0.237/32 scope global eth0
inet6 fe80::f816:3eff:fe66:7ee8/64 scope link
valid_lft forever preferred_lft forever
查看插入数据执行情况，大概有 12 秒是不可用的
Mon Jan 28 15:04:51 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:04:52 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:04:53 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:04:54 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:04:55 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:04:56 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:04:57 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:04:58 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:05:00 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:05:01 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:05:02 CST 2019
ERROR 2003 (HY000): Can’t connect to MySQL server on ‘10.0.0.237’ (111)
Mon Jan 28 15:05:03 CST 2019
失效切换成功
5 总结
使用双主 + keepalived 的优点是部署简单，双主加半同步情况下，理论上不会丢数据，适用于中小型 MySQL 集群。缺点也比较明显，就是增加从节点的情况下，从节点不会主动切换同步对象，而且脚本需要自己实现，有一定风险。
