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一、主從復(fù)制的概述；
二、同步詳解；
三、案例：配置主從復(fù)制；
概述：為了分擔(dān)讀寫(xiě)壓力，Redis支持主從復(fù)制，Redis的主從結(jié)構(gòu)可以采用一主多從或者級(jí)聯(lián)結(jié)構(gòu)，Redis主從復(fù)制可以根據(jù)是否是全量分為全量同步和增量同步。下圖為級(jí)聯(lián)結(jié)構(gòu)。
同步類型：全量同步、增量同步
1.全量同步：
Redis全量復(fù)制一般發(fā)生在Slave初始化階段，這時(shí)Slave需要將Master上的所有數(shù)據(jù)都復(fù)制一份。具體步驟如下：?
1）從服務(wù)器連接主服務(wù)器，發(fā)送SYNC命令（從服務(wù)器向主服務(wù)器初次同步時(shí)，不會(huì)影響主服務(wù)器接收客戶端的請(qǐng)求）；?
2）主服務(wù)器接收到SYNC命名后，開(kāi)始執(zhí)行BGSAVE命令生成RDB文件并使用緩沖區(qū)記錄此后執(zhí)行的所有寫(xiě)命令；?
3）主服務(wù)器BGSAVE執(zhí)行完后，向所有從服務(wù)器發(fā)送快照文件，并在發(fā)送期間繼續(xù)記錄被執(zhí)行的寫(xiě)命令；?
4）從服務(wù)器收到快照文件后丟棄所有舊數(shù)據(jù)，載入收到的快照；?
5）主服務(wù)器快照發(fā)送完畢后開(kāi)始向從服務(wù)器發(fā)送緩沖區(qū)中的寫(xiě)命令；?
6）從服務(wù)器完成對(duì)快照的載入，開(kāi)始接收命令請(qǐng)求，并執(zhí)行來(lái)自主服務(wù)器緩沖區(qū)的寫(xiě)命令；?
完成上面幾個(gè)步驟后就完成了從服務(wù)器數(shù)據(jù)初始化的所有操作，從服務(wù)器此時(shí)可以接收來(lái)自用戶的讀請(qǐng)求。
2.增量同步：
Redis增量復(fù)制是指Slave初始化后開(kāi)始正常工作時(shí)主服務(wù)器發(fā)生的寫(xiě)操作同步到從服務(wù)器的過(guò)程。?增量復(fù)制的過(guò)程主要是主服務(wù)器每執(zhí)行一個(gè)寫(xiě)命令就會(huì)向從服務(wù)器發(fā)送相同的寫(xiě)命令，從服務(wù)器接收并執(zhí)行收到的寫(xiě)命令。
同步策略：
主從剛剛連接的時(shí)候，進(jìn)行全量同步；
全同步結(jié)束后，進(jìn)行增量同步。當(dāng)然，如果有需要，slave 在任何時(shí)候都可以發(fā)起全量同步。redis 策略是，無(wú)論如何，首先會(huì)嘗試進(jìn)行增量同步，如不成功，要求從機(jī)進(jìn)行全量同步。
注：
如果多個(gè)Slave斷線了，需要重啟的時(shí)候，因?yàn)橹灰猄lave啟動(dòng)，就會(huì)發(fā)送sync請(qǐng)求和主機(jī)全量同步，當(dāng)多個(gè)同時(shí)出現(xiàn)的時(shí)候，可能會(huì)導(dǎo)致Master IO劇增導(dǎo)致宕機(jī)。
建議開(kāi)啟master主服務(wù)器的持久化功能，避免出現(xiàn)master重啟后，數(shù)據(jù)無(wú)法恢復(fù)；
實(shí)驗(yàn)步驟：
?安裝并配置master角色的redis服務(wù)；
?安裝并配置slave角色的redis服務(wù)（雙實(shí)例）；
?配置master角色的文件；
?配置slave角色的文件；
?驗(yàn)證主從復(fù)制；
?安裝并配置master角色的redis服務(wù)；
[root@master ~]# wget http://download.redis.io/releases/redis-4.0.9.tar.gz
[root@master ~]# tar zxvf redis-4.0.9.tar.gz
[root@master ~]# cd redis-4.0.9
[root@master redis-4.0.9]# make
[root@master redis-4.0.9]# echo $?
[root@master redis-4.0.9]# cd
[root@master ~]# mkdir -p /usr/local/redis
[root@master ~]# cp /root/redis-4.0.9/src/redis-server /usr/local/redis/ ##服務(wù)端程序
[root@master ~]# cp /root/redis-4.0.9/src/redis-cli /usr/local/redis/ ##客戶端程序
[root@master ~]# cp /root/redis-4.0.9/redis.conf /usr/local/redis/ ##主配置文件
[root@master ~]# ls /usr/local/redis/
redis-cli redis.conf redis-server
[root@master ~]# sed -i '/^bind 127.0.0.1$/s/127.0.0.1/192.168.100.101/g' /usr/local/redis/redis.conf
[root@master ~]# sed -i '/protected-mode/s/yes/no/g' /usr/local/redis/redis.conf ##關(guān)閉redis的保護(hù)模式
[root@master ~]# sed -i '/daemonize/s/no/yes/g' /usr/local/redis/redis.conf ##開(kāi)啟redis的后臺(tái)守護(hù)進(jìn)程模式
[root@master ~]# sed -i '/requirepass/s/foobared/123123/g' /usr/local/redis/redis.conf ##設(shè)置redis的密碼為123123
[root@master ~]# sed -i '/requirepass 123123/s/^#//g' /usr/local/redis/redis.conf ##開(kāi)啟redis的密碼
[root@master ~]# ln -s /usr/local/redis/redis-cli /usr/local/bin/redis
[root@master ~]# cat <<END >>/etc/init.d/redis
#!/bin/sh
# chkconfig: 2345 80 90
# description: Start and Stop redis
#PATH=/usr/local/bin:/sbin:/usr/bin:/bin
REDISPORT=6379
EXEC=/usr/local/redis/redis-server
REDIS_CLI=/usr/local/redis/redis-cli
PIDFILE=/var/run/redis_6379.pid
CONF="/usr/local/redis/redis.conf"
AUTH="123123"
LISTEN_IP=\$(netstat -utpln |grep redis-server |awk '{print \$4}'|awk -F':' '{print \$1}')
case "\$1" in
start)
if [ -f \$PIDFILE ]
then
echo "\$PIDFILE exists, process is already running or crashed"
else
echo "Starting Redis server..."
\$EXEC \$CONF
fi
if [ "\$?"="0" ]
then
echo "Redis is running..."
fi
;;
stop)
if [ ! -f \$PIDFILE ]
then
echo "\$PIDFILE does not exist, process is not running"
else
PID=\$(cat \$PIDFILE)
echo "Stopping ..."
\$REDIS_CLI -h \$LISTEN_IP -p \$REDISPORT -a \$AUTH SHUTDOWN
while [ -x \${PIDFILE} ]
do
echo "Waiting for Redis to shutdown ..."
sleep 1
done
echo "Redis stopped"
fi
;;
restart|force-reload)
\${0} stop
\${0} start
;;
*)
echo "Usage: /etc/init.d/redis {start|stop|restart|force-reload}" >&2
exit 1
esac
END
[root@master ~]# chmod 755 /etc/init.d/redis
[root@master ~]# chkconfig --add redis
[root@master ~]# /etc/init.d/redis start
Starting Redis server...
4390:C 04 May 02:16:45.232 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
4390:C 04 May 02:16:45.232 # Redis version=4.0.9, bits=64, commit=00000000, modified=0, pid=4390, just started
4390:C 04 May 02:16:45.232 # Configuration loaded
Redis is running...
[root@master ~]# netstat -utpln |grep redis
tcp 0 192.168.100.101:6379 0.0.0.0:* LISTEN 4204/redis-server *
[root@master ~]# redis -h 192.168.100.101 -a 123123 -p 6379
192.168.100.101:6379> exit
?安裝并配置slave角色的redis服務(wù)（雙實(shí)例）；
[root@slave ~]# wget http://download.redis.io/releases/redis-4.0.9.tar.gz
[root@slave ~]# tar zxvf redis-4.0.9.tar.gz
[root@slave ~]# cd redis-4.0.9
[root@slave redis-4.0.9]# make
[root@slave redis-4.0.9]# echo $?
[root@slave redis-4.0.9]# cd
[root@slave ~]# mkdir -p /usr/local/redis
[root@slave ~]# cp /root/redis-4.0.9/src/redis-server /usr/local/redis/ ##服務(wù)端程序
[root@slave ~]# cp /root/redis-4.0.9/src/redis-cli /usr/local/redis/ ##客戶端程序
[root@slave ~]# cp /root/redis-4.0.9/redis.conf /usr/local/redis/ ##主配置文件
[root@slave ~]# ls /usr/local/redis/
redis-cli redis.conf redis-server
[root@slave ~]# sed -i '/^bind 127.0.0.1$/s/127.0.0.1/192.168.100.102/g' /usr/local/redis/redis.conf
[root@slave ~]# sed -i '/protected-mode/s/yes/no/g' /usr/local/redis/redis.conf ##關(guān)閉redis的保護(hù)模式
[root@slave ~]# sed -i '/daemonize/s/no/yes/g' /usr/local/redis/redis.conf ##開(kāi)啟redis的后臺(tái)守護(hù)進(jìn)程模式
[root@slave ~]# sed -i '/requirepass/s/foobared/123123/g' /usr/local/redis/redis.conf ##設(shè)置redis的密碼為123123
[root@slave ~]# sed -i '/requirepass 123123/s/^#//g' /usr/local/redis/redis.conf ##開(kāi)啟redis的密碼
[root@slave ~]# cp /usr/local/redis/redis.conf /usr/local/redis/redis01.conf
[root@slave ~]# sed -i '92s/6379/6380/g' /usr/local/redis/redis01.conf ##更改監(jiān)聽(tīng)端口
[root@slave ~]# sed -i '158s/6379/6380/g' /usr/local/redis/redis01.conf ##更改PID文件
[root@slave ~]# sed -i '171s/^\(.\).\{9\}/logfile "\/usr\/local\/redis\/redis01.log"/g' /usr/local/redis/redis01.conf ##更改日志文件位置，9代表舊內(nèi)容的字節(jié)數(shù)
[root@slave ~]# ln -s /usr/local/redis/redis-cli /usr/local/bin/redis
[root@slave ~]# cat <<END >>/etc/init.d/redis
#!/bin/sh
# chkconfig: 2345 80 90
# description: Start and Stop redis
#PATH=/usr/local/bin:/sbin:/usr/bin:/bin
REDISPORT=6379
EXEC=/usr/local/redis/redis-server
REDIS_CLI=/usr/local/redis/redis-cli
PIDFILE=/var/run/redis_6379.pid
CONF="/usr/local/redis/redis.conf"
AUTH="123123"
LISTEN_IP=\$(netstat -utpln |grep redis-server |awk '{print \$4}'|awk -F':' '{print \$1}' |uniq)
case "\$1" in
start)
if [ -f \$PIDFILE ]
then
echo "\$PIDFILE exists, process is already running or crashed"
else
echo "Starting Redis server..."
\$EXEC \$CONF
fi
if [ "\$?"="0" ]
then
echo "Redis is running..."
fi
;;
stop)
if [ ! -f \$PIDFILE ]
then
echo "\$PIDFILE does not exist, process is not running"
else
PID=\$(cat \$PIDFILE)
echo "Stopping ..."
\$REDIS_CLI -h \$LISTEN_IP -p \$REDISPORT -a \$AUTH SHUTDOWN
while [ -x \${PIDFILE} ]
do
echo "Waiting for Redis to shutdown ..."
sleep 1
done
echo "Redis stopped"
fi
;;
restart|force-reload)
\${0} stop
\${0} start
;;
*)
echo "Usage: /etc/init.d/redis {start|stop|restart|force-reload}" >&2
exit 1
esac
END
[root@slave ~]# chmod 755 /etc/init.d/redis
[root@slave ~]# chkconfig --add redis
[root@slave ~]# cp /etc/init.d/redis /etc/init.d/redis01
[root@slave ~]# sed -i 's/6379/6380/g' /etc/init.d/redis01
[root@slave ~]# sed -i '/CONF=/s/redis.conf/redis01.conf/g' /etc/init.d/redis01
[root@slave ~]# /etc/init.d/redis start
Starting Redis server...
4390:C 04 May 02:16:45.232 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
4390:C 04 May 02:16:45.232 # Redis version=4.0.9, bits=64, commit=00000000, modified=0, pid=4390, just started
4390:C 04 May 02:16:45.232 # Configuration loaded
Redis is running...
[root@slave ~]# /etc/init.d/redis01 start
Starting Redis server...
4390:C 04 May 02:16:45.232 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
4390:C 04 May 02:16:45.232 # Redis version=4.0.9, bits=64, commit=00000000, modified=0, pid=4390, just started
4390:C 04 May 02:16:45.232 # Configuration loaded
Redis is running...
[root@slave ~]# netstat -utpln |grep redis
tcp 0 0 192.168.100.102:6379 0.0.0.0:* LISTEN 11864/redis-server
tcp 0 0 192.168.100.102:6380 0.0.0.0:* LISTEN 11877/redis-server
[root@ slave ~]# redis -h 192.168.100.102 -a 123123 -p 6379
192.168.100.102:6379> exit
[root@ slave ~]# redis -h 192.168.100.102 -a 123123 -p 6380
192.168.100.102:6380> exit
?配置master角色的文件；
[root@master ~]# sed -i '450s/^\(.\).\{22\}/min-slaves-to-write 2/g' /usr/local/redis/redis.conf
##設(shè)置slave節(jié)點(diǎn)的數(shù)量，如果slave節(jié)點(diǎn)數(shù)量少于此值，那么master節(jié)點(diǎn)將停止客戶端的一切寫(xiě)請(qǐng)求
[root@master ~]# sed -n '451s/^\(.\).\{22\}/min-slaves-max-lag 10/g' /usr/local/redis/redis.conf
##master與slave之間同步數(shù)據(jù)的超時(shí)時(shí)間，若超過(guò)此時(shí)間，master節(jié)點(diǎn)將停止客戶端的一切寫(xiě)操作
[root@master ~]# /etc/init.d/redis restart
Stopping ...
Redis stopped
Starting Redis server...
1638:C 15 May 16:32:08.301 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
1638:C 15 May 16:32:08.301 # Redis version=4.0.9, bits=64, commit=00000000, modified=0, pid=1638, just started
1638:C 15 May 16:32:08.301 # Configuration loaded
Redis is running...
?配置slave角色的文件；
[root@slave ~]# sed -i '281s/^\(.\).\{32\}/slaveof 192.168.100.101 6379/g' /usr/local/redis/redis.conf
##指定master的ip地址以及端口
[root@slave ~]# sed -i '288s/^\(.\).\{29\}/masterauth 123123/g' /usr/local/redis/redis.conf
##指定master的連接密碼
[root@slave ~]# /etc/init.d/redis restart
/var/run/redis_6379.pid does not exist, process is not running
Starting Redis server...
4387:C 18 May 03:24:00.027 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
4387:C 18 May 03:24:00.027 # Redis version=4.0.9, bits=64, commit=00000000, modified=0, pid=4387, just started
4387:C 18 May 03:24:00.027 # Configuration loaded
Redis is running...
[root@slave ~]# sed -i '281s/^\(.\).\{32\}/slaveof 192.168.100.101 6379/g' /usr/local/redis/redis01.conf
[root@slave ~]# sed -i '288s/^\(.\).\{29\}/masterauth 123123/g' /usr/local/redis/redis01.conf
[root@slave ~]# /etc/init.d/redis01 restart
Stopping ...
Redis stopped
Starting Redis server...
Redis is running...
?驗(yàn)證主從復(fù)制；
[root@master ~]# redis -h 192.168.100.101 -a 123123 -p 6379 ##在master節(jié)點(diǎn)上創(chuàng)建鍵值對(duì)
192.168.100.101:6379> set name xiaoming
OK
192.168.100.101:6379> keys *
1) "name"
192.168.100.101:6379> get name
"xiaoming"
192.168.100.101:6379> info replication ##查看復(fù)制信息
# Replication
role:master
connected_slaves:2
min_slaves_good_slaves:2
slave0:ip=192.168.100.102,port=6380,state=online,offset=522,lag=1
slave1:ip=192.168.100.102,port=6379,state=online,offset=522,lag=1
master_replid:46ec2c7e971d337d060d183d3a0c1313c5dd1683
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:522
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:522
192.168.100.101:6379> exit
[root@slave ~]# redis -h 192.168.100.102 -p 6379 -a 123123 ##登錄slave節(jié)點(diǎn)驗(yàn)證鍵值同步情況，并測(cè)試無(wú)法寫(xiě)入
192.168.100.102:6379> keys *
1) "name"
192.168.100.102:6379> get name
"xiaoming"
192.168.100.102:6380> set name1 xiaohong
(error) READONLY You can't write against a read only slave.
192.168.100.102:6379> exit
[root@slave ~]# redis -h 192.168.100.102 -p 6380 -a 123123
192.168.100.102:6380> keys *
1) "name"
192.168.100.102:6380> get name
"xiaoming"
192.168.100.102:6380> exit
[root@master ~]# reboot ##重啟master節(jié)點(diǎn)，驗(yàn)證redis默認(rèn)的RDB持久化
[root@master ~]# /etc/init.d/redis restart
[root@master ~]# redis -h 192.168.100.101 -a 123123 -p 6379
192.168.100.101:6379> keys *
1) "name"
192.168.100.101:6379> exit
[root@slave ~]# redis -h 192.168.100.102 -p 6380 -a 123123
192.168.100.102:6380> keys *
1) "name"
192.168.100.102:6380> get name
"xiaoming"
192.168.100.102:6380> exit
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