参与复制的Redis实例划分为主节点（master）和从节点（slave）。
默认情况下，Redis都是主节点。每个从节点只能有一个主节点，而主节点可以同时具有多个从节点。
复制的数据流是单向的，只能由主节点复制到从节点。
配置复制的方式有以下三种：
1）在配置文件中加入slaveof{masterHost}{masterPort}随Redis启动生效。
2）在redis-server启动命令后加入--slaveof{masterHost}{masterPort}生效。
3）直接使用命令：slaveof{masterHost}{masterPort}生效（配置认证：config set masterauth 123456）。
1、主节点 redis_6379
# egrep -v "^#|^$" /etc/redis.d/redis_6379.conf
bind 0.0.0.0
protected-mode yes
port 6379
tcp-backlog 511
timeout 0
tcp-keepalive 300
daemonize yes
supervised no
pidfile /var/run/redis_6379.pid
loglevel notice
logfile /var/log/redis/redis_6379.log
databases 16
save 900 1
save 300 10
save 60 10000
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump.rdb
dir /var/lib/redis_6379
slave-serve-stale-data yes
slave-read-only yes
repl-diskless-sync no
repl-diskless-sync-delay 5
repl-disable-tcp-nodelay no
slave-priority 100
requirepass 123456
appendonly no
appendfilename "appendonly.aof"
appendfsync everysec
no-appendfsync-on-rewrite no
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb
aof-load-truncated yes
lua-time-limit 5000
slowlog-log-slower-than 10000
slowlog-max-len 128
latency-monitor-threshold 0
notify-keyspace-events ""
hash-max-ziplist-entries 512
hash-max-ziplist-value 64
list-max-ziplist-size -2
list-compress-depth 0
set-max-intset-entries 512
zset-max-ziplist-entries 128
zset-max-ziplist-value 64
hll-sparse-max-bytes 3000
activerehashing yes
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
hz 10
aof-rewrite-incremental-fsync yes
2、从节点 redis_6380
# egrep -v "^#|^$" /etc/redis.d/redis_6380.conf
bind 0.0.0.0
protected-mode yes
port 6380
tcp-backlog 511
timeout 0
tcp-keepalive 300
daemonize yes
supervised no
pidfile /var/run/redis_6380.pid
loglevel notice
logfile /var/log/redis/redis_6380.log
databases 16
save 900 1
save 300 10
save 60 10000
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump.rdb
dir /var/lib/redis_6380
slave-serve-stale-data yes
slave-read-only yes
repl-diskless-sync no
repl-diskless-sync-delay 5
repl-disable-tcp-nodelay no
slave-priority 100
requirepass 123456
appendonly no
appendfilename "appendonly.aof"
appendfsync everysec
no-appendfsync-on-rewrite no
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb
aof-load-truncated yes
lua-time-limit 5000
slowlog-log-slower-than 10000
slowlog-max-len 128
latency-monitor-threshold 0
notify-keyspace-events ""
hash-max-ziplist-entries 512
hash-max-ziplist-value 64
list-max-ziplist-size -2
list-compress-depth 0
set-max-intset-entries 512
zset-max-ziplist-entries 128
zset-max-ziplist-value 64
hll-sparse-max-bytes 3000
activerehashing yes
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
hz 10
aof-rewrite-incremental-fsync yes
3、在从节点启动复制
# redis-cli -p 6380 -a 123456
127.0.0.1:6380> config set masterauth 123456
OK
127.0.0.1:6380> slaveof 127.0.0.1 6379
127.0.0.1:6380> info replication
# Replication
role:slave
master_host:192.168.1.188
master_port:6379
master_link_status:up
master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:15
slave_priority:100
slave_read_only:1
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
4、查看主节点状态
# redis-cli -p 6379 -a 123456
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.1.188,port=6380,state=online,offset=1387,lag=0
master_repl_offset:1387
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:1386
5、复制测试
127.0.0.1:6379> set name imkh
OK
127.0.0.1:6379> get name
"imkh"
127.0.0.1:6380> get name
"imkh"
6、断开复制
断开复制主要流程：
1）断开与主节点复制关系。
2）从节点晋升为主节点。
从节点断开复制后并不会抛弃原有数据，只是无法再获取主节点上的数据变化。
127.0.0.1:6380> slaveof no one
OK
127.0.0.1:6380> info replication
# Replication
role:master
connected_slaves:0
master_repl_offset:2381
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:0
master_repl_offset:2409
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:2408
7、切主操作
切主操作流程如下：
1）断开与旧主节点复制关系。
2）与新主节点建立复制关系。
3）删除从节点当前所有数据。
4）对新主节点进行复制操作。
运维提示
切主后从节点会清空之前所有的数据，线上人工操作时小心slaveof在错误的节点上执行或者指向错误的主节点。
127.0.0.1:6380> get name
"imkh"
127.0.0.1:6380> slaveof 192.168.1.188 6381
OK
127.0.0.1:6380> info replication
# Replication
role:slave
master_host:192.168.1.188
master_port:6381
master_link_status:up
master_last_io_seconds_ago:3
master_sync_in_progress:0
slave_repl_offset:1
slave_priority:100
slave_read_only:1
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
127.0.0.1:6380> get name
(nil)
127.0.0.1:6380> get age
"20"
参考：《Redis开发与运维》
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