Redis主从自动failover-ylw6006
Redis主从架构持久化存在一个问题，即前次测试的结论，持久化需要配置在主实例上才能跨越实例保证数据不丢失，这样以来主实例在持久化数据到硬盘的过程中，势必会造成磁盘的I/O等待，经过实际测试，这个持久化写硬盘的过程给应用程序带来的影响无法忍受；因而在大多数场景下，会考虑把持久化配置在从实例上，当主实例宕机后，通过手动或者自动的方式将从实例提升为主实例，继续提供服务！当主实例恢复后，先从原从实例上同步数据，同步完成后再恢复到原始的主从状态！要实现这种的要求，需要有keepalive的配合，一方面keepalive提供了VIP，可以避免修改应用程序连接，同时redis实例的配置文件监听部分也需要修改为全网监听；另一方面keepalive定时调度脚本来监控主从实例的状态，根据具体情况进行切换！本文将重点介绍下使用keepalive实现redis主从自动failover！环境介绍
操作系统版本均为：rhel5.4 64bit
redis版本：2.6.4
redis实例端口均为：6379
redis实例密码均为：123
VIP：192.168.1.120
主实例为server11(192.168.1.112)
从实例为server12(192.168.1.113，开启快照持久化)
一：安装keepalive软件,server11安装完成后直接scp至server12上即可
[*]# wget http://keepalived.org/software/keepalived-1.1.19.tar.gz
[*]# tar -zxvf ../tarbag/keepalived-1.1.19.tar.gz
[*]# cd keepalived-1.1.19/
[*]# ./configure --prefix=/usr/local/keepalived && make && make install
二：配置主节点server11配置文件
[*]# cat /usr/local/keepalived/etc/keepalived/keepalived.conf
[*]! Configuration File for keepalived
[*]
[*]global_defs {
[*] router_id LVS_DEVEL
[*]}
[*]
[*]vrrp_script Monitor_redis {
[*] script "/usr/local/scripts/redis_monitor.sh"
[*] interval 2
[*] weight 2
[*]}
[*]
[*]vrrp_instance VI_1{
[*] state MASTER
[*] interface eth0
[*] virtual_router_id 51
[*] mcast_src_ip 192.168.1.112
[*] priority100
[*] advert_int 1
[*] authentication {
[*] auth_type PASS
[*] auth_pass password_123
[*]}
[*] track_script {
[*] Monitor_redis
[*]}
[*] virtual_ipaddress {
[*] 192.168.1.120
[*] }
[*] notify_fault/usr/local/scripts/redis_fault.sh
[*] notify_stop /usr/local/scripts/redis_stop.sh
[*]
[*]}
三：配置从节点server12配置文件
[*]# cat /usr/local/keepalived/etc/keepalived/keepalived.conf
[*]! Configuration File for keepalived
[*]
[*]global_defs {
[*] router_id LVS_DEVEL
[*]}
[*]
[*]vrrp_script Monitor_redis {
[*] script "/usr/local/scripts/redis_monitor.sh"
[*] interval 2
[*] weight 2
[*]}
[*]
[*]vrrp_instance VI_1{
[*] state BACKUP
[*] interface eth0
[*] virtual_router_id 51
[*] mcast_src_ip 192.168.1.113
[*] priority99
[*] advert_int 1
[*] authentication {
[*] auth_type PASS
[*] auth_pass password_123
[*]}
[*] track_script {
[*] Monitor_redis
[*]}
[*] virtual_ipaddress {
[*] 192.168.1.120
[*] }
[*] notify_master /usr/local/scripts/redis_master.sh
[*] notify_backup /usr/local/scripts/redis_backup.sh
[*] notify_fault/usr/local/scripts/redis_fault.sh
[*] notify_stop /usr/local/scripts/redis_stop.sh
[*]
[*]}
四：准备相关的脚本，主从实例上都需要存在这些脚本，同时注意脚本需要由可执行权限
[*]# cat /usr/local/scripts/redis_monitor.sh
[*]#!/bin/bash
[*]ALIVE=$(/usr/local/redis2/bin/redis-cli -h 192.168.1.112 -p 6379 -a 123 PING)
[*]
[*]if [ "$ALIVE" == "PONG" ]; then
[*] echo $ALIVE
[*] exit 0
[*] else
[*] echo $ALIVE
[*] killall -9 keepalived
[*] service network restart
[*] exit 1
[*]fi
[*]
[*]# sh /usr/local/scripts/redis_monitor.sh
[*]PONG
[*]
[*]# cat /usr/local/scripts/redis_master.sh
[*]#!/bin/bash
[*]REDISCLI="/usr/local/redis2/bin/redis-cli -h 192.168.1.112 -p 6379 -a 123"
[*]LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log"
[*]
[*]echo "" >> $LOGFILE
[*]date >> $LOGFILE
[*]echo "Being master...." >> $LOGFILE 2>&1
[*]echo "Run SLAVEOF cmd ..." >> $LOGFILE
[*]$REDISCLI SLAVEOF 192.168.1.113 6379 >> $LOGFILE2>&1
[*]sleep 10
[*]echo "Run SLAVEOF NO ONE cmd ..." >> $LOGFILE
[*]$REDISCLI SLAVEOF NO ONE >> $LOGFILE 2>&1
[*]
[*]
[*]# cat /usr/local/scripts/redis_backup.sh
[*]#!/bin/bash
[*]REDISCLI="/usr/local/redis2/bin/redis-cli -h 192.168.1.112 -p 6379 -a 123"
[*]LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log"
[*]
[*]echo "" >> $LOGFILE
[*]date >> $LOGFILE
[*]echo "Being slave...." >> $LOGFILE 2>&1
[*]sleep 15
[*]echo "Run SLAVEOF cmd ..." >> $LOGFILE
[*]$REDISCLI SLAVEOF 192.168.1.113 6379 >> $LOGFILE2>&1
[*]
[*]# cat /usr/local/scripts/redis_stop.sh
[*]#!/bin/bash
[*]LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log"
[*]echo "" >> $LOGFILE
[*]date >> $LOGFILE
[*]# cat /usr/local/scripts/redis_fault.sh #!/bin/bash
LOGFILE="/usr/local/redis2/var/keepalived-redis-state.log"
echo "" >> $LOGFILE
date >> $LOGFILE
五：主从实例分别启动keepalive进程，测试VIP是否正常(这里就要修改redis配置文件的监听地址为0.0.0.0)
[*]# /usr/local/keepalived/sbin/keepalived -D -f/usr/local/keepalived/etc/keepalived/keepalived.conf
[*]# tail -f /var/log/messages
[*]Dec 12 09:25:49 server11 Keepalived_healthcheckers: Configuration is using : 5499 Bytes
[*]Dec 12 09:25:49 server11 Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...
[*]Dec 12 09:25:49 server11 Keepalived_vrrp: VRRP sockpool:
[*]Dec 12 09:25:49 server11 Keepalived_vrrp: VRRP_Script(Monitor_redis) succeeded
[*]Dec 12 09:25:50 server11 Keepalived_vrrp: VRRP_Instance(VI_1{) Transition to MASTER STATE
[*]Dec 12 09:25:51 server11 Keepalived_vrrp: VRRP_Instance(VI_1{) Entering MASTER STATE
[*]Dec 12 09:25:51 server11 Keepalived_vrrp: VRRP_Instance(VI_1{) setting protocol VIPs.
[*]Dec 12 09:25:51 server11 Keepalived_vrrp: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120
[*]Dec 12 09:25:51 server11 avahi-daemon: Registering new address record for 192.168.1.120 on eth0.
[*]Dec 12 09:25:51 server11 Keepalived_healthcheckers: Netlink reflector reports IP 192.168.1.120 added
[*]Dec 12 09:25:51 server11 Keepalived_vrrp: Netlink reflector reports IP 192.168.1.120 added
[*]Dec 12 09:25:56 server11 Keepalived_vrrp: VRRP_Instance(VI_1{) Sending gratuitous ARPs on eth0 for 192.168.1.120
[*]
[*]# ip a |grep 192
[*] inet 192.168.1.112/24 brd 192.168.1.255 scope global eth0
[*] inet 192.168.1.120/32 scope global eth0
[*]
[*]# /usr/local/keepalived/sbin/keepalived -D -f /usr/local/keepalived/etc/keepalived/keepalived.conf
[*]# tail -f /var/log/messages
[*]Dec 12 09:26:55 server12 Keepalived_healthcheckers: Configuration is using : 5595 Bytes
[*]Dec 12 09:26:55 server12 Keepalived_vrrp: VRRP_Instance(VI_1{) Entering BACKUP STATE
[*]Dec 12 09:26:55 server12 Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...
[*]Dec 12 09:26:55 server12 Keepalived_vrrp: VRRP sockpool:
[*]Dec 12 09:26:55 server12 Keepalived_vrrp: VRRP_Script(Monitor_redis) succeeded
[*]
[*]# /usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 info |grep -A 3 'Replication'
[*]# Replication
[*]role:master
[*]connected_slaves:1
[*]slave0:192.168.1.113,6379,online
六：主实例写入测试数据，该脚本原则上会写入25条测试数据，不过由于未优化redis默认并发数，会导致一些写入请求失败，最终功写入231839条测试数据，占内存总大小为25M左右，写入过程中可以观察主从实例的持久化文件变化情况，主实例的持久化文件维持在30k，从实例的则不断的扩展！
[*]# cat test.sh
[*]#!/bin/bash
[*]REDISCLI="/usr/local/redis2/bin/redis-cli -h 192.168.1.120 -a 123 -n 1 SET"
[*]ID=1
[*]while(($ID
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