一、Redis主从同步
1.什么是主从同步
主库：只负责写数据
从库：只负责读数据(从库手动，配置文件配置)
主库只要发生更改，数据就会同步到从库
2.主从同步原理
- 副本库通过slaveof 127.0.0.1 6379命令,连接主库,并发送SYNC给主库
- 主库收到SYNC,会立即触发BGSAVE,后台保存RDB,发送给副本库
- 副本库接收后会应用RDB快照
- 主库会陆续将中间产生的新的操作,保存并发送给副本库
- 到此,我们主复制集就正常工作了
- 再此以后,主库只要发生新的操作,都会以命令传播的形式自动发送给副本库
- 所有复制相关信息,从info信息中都可以查到.即使重启任何节点,他的主从关系依然都在
- 如果发生主从关系断开时,从库数据没有任何损坏,在下次重连之后,从库发送PSYNC给主库
- 主库只会将从库缺失部分的数据同步给从库应用,达到快速恢复主从的目的
3.主从复制存在的问题
主从复制，主节点发生故障，需要做故障转移，可以手动转移：让其中一个slave变成master(哨兵)
主从复制，只能主写数据库，所以写的能力和存储能力有限(集群)
原理
1.多个sentinel（哨兵）发现并确认master有问题
2.选举出一个sentinel作为领导
3.选取一个slave作为新的master
4.通知其余slave成为新的master的slave
5.通知客户端主从变化
6.等待老的master复活成为新master的slave
二、搭建主从，配置哨兵
1.Docker拉取CentOS容器，作为本机
docker run -dit --name centos01 -p 6379:6379 -p 6380:6380 -p 6381:6381 -p 26379:26379 -p 26380:26380 -p 26381:26381 centos:7.9.2009
2.进入容器
docker exec -it centos01 bash
3.安装redis
# 1.前往用户根目录 cd ~ # 2.更换yum源，下载redis-5.0.7 curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo # 安装需要的依赖 yum install gcc vim wget make -y wget http://download.redis.io/releases/redis-5.0.7.tar.gz # 觉得安装慢的可以先下载下来，然后复制进去 docker cp /mnt/d/X_Settings/redis/redis-5.0.7.tar.gz centos01:/root/ # 3.解压安装包 tar -xzf redis-5.0.7.tar.gz # 4.进入目标文件 cd redis-5.0.7 # 5.编译安装 make && make install # 如果出现：[Errno 256] No more mirrors to try 错误 yum clean all yum makecache # 6.复制环境到指定路径完成安装 cp -r ~/redis-5.0.7 /usr/local/redis # 7.建立软连接 ln -s /usr/local/redis/src/redis-server /usr/bin/redis-server ln -s /usr/local/redis/src/redis-cli /usr/bin/redis-cli ln -s /usr/local/redis/src/redis-sentinel /usr/bin/redis-sentinel # 配置文件 vim /usr/local/redis/redis.conf # 修改 daemonize yes # 8.后台运行redis cd /usr/local/redis redis-server & # ctrl + c 停止 # 9.测试redis环境 redis-cli # ctrl + c 停止 # 10.关闭redis服务 pkill -f redis -9
删除#开头和空行后的redis.conf
bind 127.0.0.1 protected-mode yes port 6379 tcp-backlog 511 timeout 0 tcp-keepalive 300 daemonize no supervised no pidfile /var/run/redis_6379.pid loglevel notice logfile "" databases 16 always-show-logo yes save 900 1 save 300 10 save 60 10000 stop-writes-on-bgsave-error yes rdbcompression yes rdbchecksum yes dbfilename dump.rdb dir ./ replica-serve-stale-data yes replica-read-only yes repl-diskless-sync no repl-diskless-sync-delay 5 repl-disable-tcp-nodelay no replica-priority 100 lazyfree-lazy-eviction no lazyfree-lazy-expire no lazyfree-lazy-server-del no replica-lazy-flush no 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 aof-use-rdb-preamble 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 stream-node-max-bytes 4096 stream-node-max-entries 100 activerehashing yes client-output-buffer-limit normal 0 0 0 client-output-buffer-limit replica 256mb 64mb 60 client-output-buffer-limit pubsub 32mb 8mb 60 hz 10 dynamic-hz yes aof-rewrite-incremental-fsync yes rdb-save-incremental-fsync yes
4.创建文件夹，编写配置文件
cd ~
mkdir master6379 slave6380 slave6381
主master 6379
vim redis_6379.conf
daemonize yes bind 0.0.0.0 port 6379 logfile redis6379.log dbfilename dump.rdb dir /root/master6379
从slave 6380
vim redis_6380.conf
daemonize yes pidfile redis.pid bind 0.0.0.0 port 6380 logfile redis6380.log dbfilename dump.rdb dir /root/slave6380 slaveof 127.0.0.1 6379 slave-read-only yes
从 slave 6381
vim redis_6381.conf
daemonize yes pidfile redis.pid bind 0.0.0.0 port 6381 logfile redis6381.log dbfilename dump.rdb dir /root/slave6381 slaveof 127.0.0.1 6379 slave-read-only yes
5.启动一主二从
redis-server redis_6379.conf redis-server redis_6380.conf redis-server redis_6381.conf # 查看redis进程 ps aux | grep redis
6.编写哨兵配置
创建文件夹
cd ~
mkdir sentinel1 sentinel2 sentinel3
主哨兵 26379
vim sentinel_26379.conf
port 26379 daemonize yes dir /root/sentinel1 bind 0.0.0.0 logfile "sentinel_6379.log" sentinel monitor mymaster 127.0.0.1 6379 2 sentinel down-after-milliseconds mymaster 30000 sentinel parallel-syncs mymaster 1 sentinel failover-timeout mymaster 180000
从哨兵26380
vim sentinel_26380.conf
port 26380 daemonize yes dir /root/sentinel1 bind 0.0.0.0 logfile "sentinel_6380.log" sentinel monitor mymaster 127.0.0.1 6380 2 sentinel down-after-milliseconds mymaster 30000 sentinel parallel-syncs mymaster 1 sentinel failover-timeout mymaster 180000
从哨兵26381
vim sentinel_26381.conf
port 26381 daemonize yes dir /root/sentinel1 bind 0.0.0.0 logfile "sentinel_6381.log" sentinel monitor mymaster 127.0.0.1 6381 2 sentinel down-after-milliseconds mymaster 30000 sentinel parallel-syncs mymaster 1 sentinel failover-timeout mymaster 180000
7.启动三个哨兵
redis-sentinel sentinel_26379.conf redis-sentinel sentinel_26380.conf redis-sentinel sentinel_26381.conf # 查看redis-sentinel进程 ps aux | grep redis-sentinel
三、代码
import redis from redis.sentinel import Sentinel # 连接哨兵服务器(主机名也可以用域名) sentinel = Sentinel([('172.25.111.89', 26379), ('172.25.111.89', 26380), ('172.25.111.89', 26381)], socket_timeout=5) # print(sentinel) # # 获取主服务器地址 master = sentinel.discover_master('mymaster') print(master) # 获取从服务器地址 slave = sentinel.discover_slaves('mymaster') print(slave) # 读写分离 # 获取主服务器进行写入 master = sentinel.master_for('mymaster', socket_timeout=5) w_ret = master.set('foo', 'bar') slave = sentinel.slave_for('mymaster', socket_timeout=0.5) r_ret = slave.get('foo') print(r_ret)
