Building Redis Cluster with docker-compose

Redis is very notorious key-value store, very fast and stable. However, there are some situations which we need real time applications and scale up our application in some high traffic moments.

Bellow I paste my final docker-compose file and to explain some important parts. In that case, my application is build on NodeJS with MariaDb.

version: '3.5'
services:
  app:
    build:
      context: ./
      dockerfile: Dockerfile
    ports:
      - 3000:3000
    environment:
      REDIS_NODE_1: redis-node-1:6373
      REDIS_NODE_2: redis-node-2:6374
      REDIS_NODE_3: redis-node-3:6375
      REDIS_NODE_4: redis-node-4:6376
      REDIS_NODE_5: redis-node-5:6377
      REDIS_NODE_6: redis-node-6:6378
    volumes:
      - '.:/usr/src/app'
      - nodemodules:/usr/local/app/node_modules
    networks:
      app_subnet:
        ipv4_address: 172.20.0.10
    depends_on:
      - db
      - redis-cluster
db:
    image: mariadb
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: feedback
      MYSQL_DATABASE: feedback
      MYSQL_USER: feedback
      MYSQL_PASSWORD: feedback
    volumes:
      - db-data:/var/lib/mysql
    ports:
      - 3306:3306
    networks:
      app_subnet:
        ipv4_address: 172.20.0.20
redis-cluster:
    image: 'redis:6.0-alpine'
    command: redis-cli --cluster create 172.20.0.31:6373 172.20.0.32:6374 172.20.0.33:6375 172.20.0.34:6376 172.20.0.35:6377 172.20.0.36:6378 --cluster-replicas 1 --cluster-yes
    networks:
      app_subnet:
        ipv4_address: 172.20.0.30
    depends_on:
      - redis-node-1
      - redis-node-2
      - redis-node-3
      - redis-node-4
      - redis-node-5
      - redis-node-6
redis-node-1:
    image: 'redis:6.0-alpine'
    command: redis-server /usr/local/etc/redis/redis.conf
    ports:
      - '6373:6373'
    volumes:
      - redis-node-1-data:/var/lib/redis
      - ./docker/redis-node-1.conf:/usr/local/etc/redis/redis.conf
    networks:
      app_subnet:
        ipv4_address: 172.20.0.31
redis-node-2:
    image: 'redis:6.0-alpine'
    command: redis-server /usr/local/etc/redis/redis.conf
    ports:
      - '6374:6374'
    volumes:
      - redis-node-2-data:/var/lib/redis
      - ./docker/redis-node-2.conf:/usr/local/etc/redis/redis.conf
    networks:
      app_subnet:
        ipv4_address: 172.20.0.32
redis-node-3:
    image: 'redis:6.0-alpine'
    command: redis-server /usr/local/etc/redis/redis.conf
    ports:
      - '6375:6375'
    volumes:
      - redis-node-3-data:/var/lib/redis
      - ./docker/redis-node-3.conf:/usr/local/etc/redis/redis.conf
    networks:
      app_subnet:
        ipv4_address: 172.20.0.33
redis-node-4:
    image: 'redis:6.0-alpine'
    command: redis-server /usr/local/etc/redis/redis.conf
    ports:
      - '6376:6376'
    volumes:
      - redis-node-4-data:/var/lib/redis
      - ./docker/redis-node-4.conf:/usr/local/etc/redis/redis.conf
    networks:
      app_subnet:
        ipv4_address: 172.20.0.34
redis-node-5:
    image: 'redis:6.0-alpine'
    command: redis-server /usr/local/etc/redis/redis.conf
    ports:
      - '6377:6377'
    volumes:
      - redis-node-5-data:/var/lib/redis
      - ./docker/redis-node-5.conf:/usr/local/etc/redis/redis.conf
    networks:
      app_subnet:
        ipv4_address: 172.20.0.35
redis-node-6:
    image: 'redis:6.0-alpine'
    command: redis-server /usr/local/etc/redis/redis.conf
    ports:
      - '6378:6378'
    volumes:
      - redis-node-6-data:/var/lib/redis
      - ./docker/redis-node-6.conf:/usr/local/etc/redis/redis.conf
    networks:
      app_subnet:
        ipv4_address: 172.20.0.36
volumes:
  db-data:
  redis-node-1-data:
  redis-node-2-data:
  redis-node-3-data:
  redis-node-4-data:
  redis-node-5-data:
  redis-node-6-data:
  nodemodules:
networks:
  app_subnet:
    driver: bridge
    ipam:
      config:
        - subnet: 172.20.0.0/24

1 —Static IP

Static IP is required because redis-cluster doesn't works with domains. In that case, I have to create a docker subnet network to make all redis nodes together in the same network

In addition, I have to set port for each redis node to avoid port collision inside docker network.

Moreover, the same port specified on docker-compose ports argument must be the same port specified on redis.conf file

Let's take a look of redis.conf file

port 6373
cluster-enabled yes
cluster-config-file nodes.conf
cluster-node-timeout 5000
appendonly yes

I have to create a redis.conf for each node available in the cluster. I my situation, I have 6 redis nodes, so I need 6 redis.conf files.

The only difference among all redis.conf files is port number. Pay attention to ensure port number the same inside redis.conf file and ports arguments in docker-compose.yml

2 —Mount Redis data volume

It's make data available to whole cluster and application when containers start over again

3 — Docker container to create the cluster

When all redis node are up, I have to join all them in a cluster. To achieve it, I create redis-cluster service to run redis-cli cluster command.

Remember, as I said before, redis-cli cluster only works with static IP, so when I have to pay attention on IP and ports values.

The purpose of the service is only to run redis-cli cluster. There is no problem service dies when the command has been finished

Final thoughts

My article is focused on Redis cluster, so of that, I don’t explain anything about NodeJs and Mariadb services.

However, feel free to ask me for information about it. It Will be a pleasure to help you :)

References:

• https://iamvishalkhare.medium.com/create-a-redis-cluster-faa89c5a6bb4
• https://www.dltlabs.com/blog/how-to-setup-configure-a-redis-cluster-easily-573120
• https://serverfault.com/questions/812156/redis-cluster-error-moved