redis-cluster

Redis sentinel with Docker Compose

Using Docker Compose to setup a redis cluster with sentinel.

This project was inspired by the project of @mdevilliers

Prerequisite

Install Docker and Docker Compose in testing environment.

If you are using Windows, please execute the following command before "git clone" to disable changing the line endings of script files into DOS format:

git config --global core.autocrlf false

Docker Compose template of Redis cluster

The template defines the topology of the Redis cluster:

services:
  master:
    image: redis:latest
    container_name: redis-master
    networks:
      - redis-net

  slave:
    image: redis:latest
    command: redis-server --slaveof redis-master 6379
    depends_on:
    - master
    networks:
      - redis-net

  sentinel:
    build:
      context: ./sentinel
      dockerfile: Dockerfile
    environment:
    - SENTINEL_DOWN_AFTER=5000
    - SENTINEL_FAILOVER=5000
    depends_on:
    - master
    - slave
    networks:
      - redis-net

networks:
  redis-net:
    driver: bridge

Notes:

1. Updated the version format to '3.9'.
2. Added the container_name parameter for each service to specify container names.
3. Replaced use of links with depends_on to define dependencies between services.
4. The Dockerfile path for the sentinel service is specified in the build parameter.
5. The path to the build context for sentinel services is specified in the context parameter.
6. The redis:latest image is used instead of a specific version to get the latest available version of Redis.
7. The declaration of links for the slave service has been removed, since it is already defined in the command section.

Please make sure the Dockerfile path for the sentinel service and the build context (./sentinel) are correctly specified and refer to your project file structure.

There are following services in the cluster:

• master: Redis master
• slave: Redis slave
• sentinel: Redis sentinel

The sentinels are configured with a "mymaster" instance with the following properties:

sentinel monitor mymaster redis-master 6379 2
sentinel down-after-milliseconds mymaster 5000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 5000

The details could be found in sentinel/sentinel.conf.

The default values of the environment variables for Sentinel are as following:

• SENTINEL_QUORUM: 2
• SENTINEL_DOWN_AFTER: 30000
• SENTINEL_FAILOVER: 180000

Play with it

Build the sentinel Docker image:

docker compose build .

Start the redis cluster:

docker compose up -d

Check the status of redis cluster:

docker compose ps

The result is:

         Name                        Command               State          Ports        
--------------------------------------------------------------------------------------
redis-cluster-sentinel-1  sentinel-entrypoint… redis ...   Up      26379/tcp, 6379/tcp 
redis-cluster-slave-1     docker-entrypoint.sh redis ...   Up      6379/tcp     
redis-master              docker-entrypoint.sh redis ...   Up      6379/tcp            

Scale out the instance number of sentinel:

docker compose scale sentinel=3

Scale out the instance number of slaves:

docker compose scale slave=2

Check the status of redis cluster:

docker compose ps

The result is:

         Name                        Command               State          Ports        
--------------------------------------------------------------------------------------
redis-cluster-sentinel-1   sentinel-entrypoint… redis ...   Up      26379/tcp, 6379/tcp 
redis-cluster-sentinel-2   sentinel-entrypoint… redis ...   Up      26379/tcp, 6379/tcp 
redis-cluster-sentinel-3   sentinel-entrypoint… redis ...   Up      26379/tcp, 6379/tcp 
redis-cluster-slave-1      docker-entrypoint.sh redis ...   Up      6379/tcp            
redis-cluster-slave-2      docker-entrypoint.sh redis ...   Up      6379/tcp            
redis-master               docker-entrypoint.sh redis ...   Up      6379/tcp            

Execute the test scripts:

./test.sh

to simulate stop and recover the Redis master. And you will see the master is switched to slave automatically.

Or, you can do the test manually to pause/unpause redis server through:

docker pause redis-master
docker unpause redis-master

And get the sentinel infomation with following commands:

docker exec redis-cluster-sentinel-1 redis-cli -p 26379 SENTINEL get-master-addr-by-name mymaster

---

master ip

docker inspect -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' redis-master

References

1: https://github.com/mdevilliers/docker-rediscluster
2: https://registry.hub.docker.com/r/bitnami/redis-sentinel
3: https://docs.docker.com/compose/
4: https://www.docker.com

License

Apache 2.0 license