docker compose部署主从复制的实现

目录

• 配置解析
• 服务搭建
• 目录结构
• Compose File
• 实例配置
• 启动服务
• 测试

受限于 Redis 单点性能，加上我们对数据天生就有的备份的需求，因此 Redis 提供了主从复制的服务。

本文记录了通过 docker compose 搭建一主双从的 Redis 服务。

配置解析

################################# REPLICATION #################################

# 【Slave】连接 Master 的配置
# slaveof 172.25.0.101 6379

# 【Slave】只读模式
# slave-read-only yes

# 【Slave】密码
# masterauth <master-password>

# 【Slave】复制期间是否允许响应查询，可能会返回脏数据
# slave-serve-stale-data yes

# 【Slave】Slave 晋级为 Master 的优先级，仅哨兵模式下生效
# slave-priority 100

# 【Slave】Slave 向 Master 报告的自己的 IP
# slave-announce-ip 5.5.5.5

# 【Slave】Slave 向 Master 报告的自己的端口
# slave-announce-port 1234

# 【Slave】Slave ping Master 的时间间隔
# repl-ping-slave-period 10

# 【Master/Slave】超时时间
# repl-timeout 60

# 【Master】Diskless 就是直接将要复制的 RDB 文件写入到 Socket 中，而不会先存储到磁盘上
repl-diskless-sync no

# 【Master】若开启 Diskless，会等待指定秒之后再进行复制，以便让更多客户端可以在窗口期内连接，并行传送
# repl-diskless-sync-delay 5

# 【Master】是否开启 Nagle 算法，可以减少流量占用，但会同步得慢些
repl-disable-tcp-nodelay no

# 【Master】环形缓冲日志的大小，给 Slave 断开之后重连使用，避免全量复制，默认 1mb
# repl-backlog-size 1mb

# 【Master】当 Master 断连所有 Slave 指定时间后，Master 会清空 backlog
# repl-backlog-ttl 3600

# 【Master】当低于指定个 Slave 连接时，Master 拒绝所有写操作
# min-slaves-to-write 3

# 【Master】当延迟高于指定秒数时，Master 拒绝所有写操作
# min-slaves-max-lag 10

服务搭建

目录结构

replication/
├── docker-compose.yml
├── master
│   ├── data
│   └── redis.conf
├── slave1
│   ├── data
│   └── redis.conf
└── slave2
    ├── data
    └── redis.conf

Compose File

定义了一个子网，方便操作，对外暴露 6371（Master）、6372、6373 端口。

version: "3"

networks:
  redis-replication:
    driver: bridge
    ipam:
      config:
        - subnet: 172.25.0.0/24

services:
  master:
    image: redis
    container_name: redis-master
    ports:
      - "6371:6379"
    volumes:
      - "./master/redis.conf:/etc/redis.conf"
      - "./master/data:/data"
    command: ["redis-server", "/etc/redis.conf"]
    restart: always
    networks:
      redis-replication:
        ipv4_address: 172.25.0.101

  slave1:
    image: redis
    container_name: redis-slave-1
    ports:
      - "6372:6379"
    volumes:
      - "./slave1/redis.conf:/etc/redis.conf"
      - "./slave1/data:/data"
    command: ["redis-server", "/etc/redis.conf"]
    restart: always
    networks:
      redis-replication:
        ipv4_address: 172.25.0.102

  slave2:
    image: redis
    container_name: redis-slave-2
    ports:
      - "6373:6379"
    volumes:
      - "./slave2/redis.conf:/etc/redis.conf"
      - "./slave2/data:/data"
    command: ["redis-server", "/etc/redis.conf"]
    restart: always
    networks:
      redis-replication:
        ipv4_address: 172.25.0.103

实例配置

Master：

基本不用配置，最简单的是指定一个端口就好了。

port 6379
protected-mode no

repl-diskless-sync no
repl-disable-tcp-nodelay no

Slave：

实例的配置保持一致就可以了，因为定义了子网，不存在端口冲突。

port 6379
protected-mode no

slaveof 172.25.0.101 6379
slave-read-only yes
slave-serve-stale-data yes

启动服务

ocker-compose up -d
Creating network "replication_redis-replication" with driver "bridge"
Creating redis-slave-1 ... done
Creating redis-master  ... done
Creating redis-slave-2 ... done

查看 Master 日志，可以看到接受了两个 Slave 的复制请求：

1:M 18 Aug 2021 15:50:31.772 * Replica 172.25.0.102:6379 asks for synchronization
1:M 18 Aug 2021 15:50:31.772 * Full resync requested by replica 172.25.0.102:6379
1:M 18 Aug 2021 15:50:31.772 * Replication backlog created, my new replication IDs are '5d27746f14ee9be9694d794f96de6ba14a669dd1' and '0000000000000000000000000000000000000000'
1:M 18 Aug 2021 15:50:31.772 * Starting BGSAVE for SYNC with target: disk
1:M 18 Aug 2021 15:50:31.773 * Background saving started by pid 19
19:C 18 Aug 2021 15:50:31.777 * DB saved on disk
19:C 18 Aug 2021 15:50:31.777 * RDB: 0 MB of memory used by copy-on-write
1:M 18 Aug 2021 15:50:31.822 * Background saving terminated with success
1:M 18 Aug 2021 15:50:31.823 * Synchronization with replica 172.25.0.102:6379 succeeded
1:M 18 Aug 2021 15:50:32.170 * Replica 172.25.0.103:6379 asks for synchronization
1:M 18 Aug 2021 15:50:32.170 * Full resync requested by replica 172.25.0.103:6379
1:M 18 Aug 2021 15:50:32.170 * Starting BGSAVE for SYNC with target: disk
1:M 18 Aug 2021 15:50:32.171 * Background saving started by pid 20
20:C 18 Aug 2021 15:50:32.175 * DB saved on disk
20:C 18 Aug 2021 15:50:32.175 * RDB: 0 MB of memory used by copy-on-write
1:M 18 Aug 2021 15:50:32.225 * Background saving terminated with success
1:M 18 Aug 2021 15:50:32.226 * Synchronization with replica 172.25.0.103:6379 succeeded

查看 Slave 日志，可以看到连接建立的全过程：

1:S 18 Aug 2021 15:50:31.771 * Connecting to MASTER 172.25.0.101:6379
1:S 18 Aug 2021 15:50:31.771 * MASTER <-> REPLICA sync started
1:S 18 Aug 2021 15:50:31.771 * Non blocking connect for SYNC fired the event.
1:S 18 Aug 2021 15:50:31.771 * Master replied to PING, replication can continue...
1:S 18 Aug 2021 15:50:31.772 * Partial resynchronization not possible (no cached master)
1:S 18 Aug 2021 15:50:31.773 * Full resync from master: 5d27746f14ee9be9694d794f96de6ba14a669dd1:0
1:S 18 Aug 2021 15:50:31.823 * MASTER <-> REPLICA sync: receiving 175 bytes from master to disk
1:S 18 Aug 2021 15:50:31.823 * MASTER <-> REPLICA sync: Flushing old data
1:S 18 Aug 2021 15:50:31.823 * MASTER <-> REPLICA sync: Loading DB in memory
1:S 18 Aug 2021 15:50:31.828 * Loading RDB produced by version 6.2.5
1:S 18 Aug 2021 15:50:31.828 * RDB age 0 seconds
1:S 18 Aug 2021 15:50:31.828 * RDB memory usage when created 1.83 Mb
1:S 18 Aug 2021 15:50:31.829 * MASTER <-> REPLICA sync: Finished with success

测试

登录 Master，尝试写入新 Key。

127.0.0.1:6371> set hello world
OK

登录 Slave，查看能否读取到：

127.0.0.1:6372> get hello
"world"

Slave 尝试写操作：

127.0.0.1:6372> set hello redis
(error) READONLY You can't write against a read only replica.

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