主从复制

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作用

  1. 数据副本
  2. 扩展读性能

一主多从，一从只能有一个主节点

数据从 主节点 单向流向 从节点

实现方式

  1. slaveof 命令 (取消 slaveof no one)
  2. 配置
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slaveof ip port 
slave-read-only yes

测试

一般不建议将 主从 放在同一主机上
redis-6379.conf 示例

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bind 127.0.0.1
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
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes
dbfilename dump-6379.rdb
dir /var/lib/redis
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
appendonly no
appendfilename "appendonly-6379.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

redis-6380.conf

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slaveof 127.0.0.1 6379

查看信息

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root@tj:~# redis-server redis-6380.conf
root@tj:~#   redis-cli -p 6380 info replication
# Replication
role:slave
master_host:127.0.0.1
master_port:6379
master_link_status:up
master_last_io_seconds_ago:3
master_sync_in_progress:0
slave_repl_offset:210
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:fa8a9a58b8cd9209163293f46f5d4b534a157163
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:210
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:210

root@tj:~# redis-cli  info replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6380,state=online,offset=336,lag=0
master_replid:fa8a9a58b8cd9209163293f46f5d4b534a157163
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:336
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:336

查看同步

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root@tj:~# redis-cli
127.0.0.1:6379> set hello world
OK
127.0.0.1:6379> exit

root@tj:~# redis-cli -p 6380 get hello
"world"

root@tj:~#  redis-cli -p 6380 set hello java
(error) READONLY You can't write against a read only replica.

root@tj:~#  redis-cli -p 6380  slaveof no one  # 取消
OK
root@tj:~# redis-cli -p 6380 info replication
# Replication
role:master
connected_slaves:0
master_replid:a4ff8594101ef9742847344ca7e6ae80deb3cff7
master_replid2:fa8a9a58b8cd9209163293f46f5d4b534a157163
master_repl_offset:997
second_repl_offset:941
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:997

root@tj:~#  redis-cli -p 6380 set hello java
OK

runId 与 偏移量

runId 标识，会在重启后发生过改变

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redis-cli -p 6379 info server |grep run

备节点 感知主节点 runId 变化后，会全量复制

偏移量： 主备 偏移量达到一致的时候，数据一致