With MySQL replication and keepalived, we can setup a quite robust high available MySQL environment in a few steps:
Environment:
Host1: db01.wordpress.com
Host2: db02.wordpress.com
DBVIP: mysql.wordpress.com 10.0.0.1
1. Setup MySQL Master-Master replication
Ref: Setup MySQL replication
2. Install keepalived at both hosts
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--using apt-get, for Ubuntu
apt-get install keepalived
--using yum, for Redhat
yum install keepalive
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3. Config keepalived
1) Add keepalived config file /etc/keepalived/keepalived.conf
Config file for host db01:
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! Configuration File for keepalived
global_defs {
notification_email {
alexzeng@wordpress.com
}
notification_email_from alexzeng@wordpress.com
smtp_server mx.wordpress.com
smtp_connect_timeout 30
router_id mysql-ha
}
vrrp_script check_mysql {
script "/mysql/keepalived_check.sh db02.wordpress.com"
interval 2
weight 2
}
vrrp_instance VI_1 {
state BACKUP
interface eth1
virtual_router_id 51
priority 100
advert_int 1
nopreempt
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
check_mysql
}
virtual_ipaddress {
10.0.0.1/24 dev eth1 label eth1:1
}
notify_master /mysql/keepalived_master.sh
notify_backup /mysql/keepalived_backup.sh
}
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Config file of host db02:
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Copy the config file in db01, and change this line:From script "/mysql/keepalived_check.sh db02.wordpress.com"to script "/mysql/keepalived_check.sh db01.wordpress.com"
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2) Add scripts to both nodes
/mysql/keepalived_check.sh : monitor MySQL (for the host/network down, keepalived has internal mechanism to monitor them)
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#!/bin/bash
export MYSQL_HOME=/mysql
export PATH=$MYSQL_HOME/bin:$PATH
mysql="$MYSQL_HOME/bin/mysql"
delay_file="$MYSQL_HOME/slave_delay_second.log"
slave_host=$1
$mysql -u root --connect_timeout=3 --execute="select version();"
if [ $? -ne 0 ]; then
delayseconds=`cat $delay_file`
if [ $delayseconds -le 120 ]; then
/etc/init.d/keepalived stop
fi
exit 1
fi
$mysql -urepluser -prepluser -h$slave_host --connect_timeout=3 -e"select version();"
if [ $? -eq 0 ]; then
delayseconds=`$mysql -urepluser -prepluser -h$slave_host --connect_timeout=3 -e"show slave status\G"|grep Seconds_Behind_Master|awk '{print \$2}'`
if [[ "$delayseconds" =~ ^[0-9]+$ ]] ; then
echo "$delayseconds" > $delay_file
else
echo "9999" > $delay_file
fi
fi
exit 0
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/mysql/keepalived_master.sh : it will be called when the node becomes master
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#!/bin/bash
my_host=`hostname`
current_date=`/bin/date +"%b %d %H:%M:%S"`
From="$my_host"
mail_list=alexzeng@wordpress.com
Subject="$my_host is MASTER"
Msgboday="$current_date : mysql.wordpress.com is online at $my_host"
echo "$Msgboday" | /usr/bin/mailx -s "$Subject" "$mail_list"
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/mysql/keepalived_backup.sh : it will be called when the node becomes slave
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#!/bin/bash
my_host=`hostname`
current_date=`/bin/date +"%b %d %H:%M:%S"`
From="$my_host"
mail_list=alexzeng@wordpress.com
Subject="$my_host is BACKUP"
Msgboday="$current_date : mysql.wordpress.com is offline at $my_host"
echo "$Msgboday" | /usr/bin/mailx -s "$Subject" "$mail_list"
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4. Start keepalived at both nodes
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service keepalived start
or
/etc/init.d/keepalived start
Check its log file at /var/log/messages
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5. Test it
Scenarios:
A. Stop MySQL at the master node
B. Shutdown master node network
C. Shutdown master node OS
D. Split-brain (the nodes cannot connect to each other) – In my test, keepalived didn’t do anything in this situation.
Check result:
1) Check emails
2) Check IP using ifconfig at both nodes
2) Connect to DB without stop:
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while true loop
do
date
mysql -urepluser -prepluser -hmysql.wordpress.com -e"select @@hostname;"
sleep 1
done;
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In my test, the db cannot be connected for just 2 seconds.
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Mon Oct 29 22:30:51 GMT+7 2012
+---------------+
| @@hostname |
+---------------+
| db01 |
+---------------+
Mon Oct 29 22:30:52 GMT+7 2012
ERROR 2003 (HY000): Can't connect to MySQL server on 'mysql.wordpress.com' (111)
Mon Oct 29 22:30:53 GMT+7 2012
ERROR 2003 (HY000): Can't connect to MySQL server on 'mysql.wordpress.com' (111)
Mon Oct 29 22:30:54 GMT+7 2012
+---------------+
| @@hostname |
+---------------+
| db02 |
+---------------+
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本文转自 运维小当家 51CTO博客，原文链接：http://blog.51cto.com/solin/1951808，如需转载请自行联系原作者
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