Redis connection refused between Vagrant and Docker - docker

Question

I have a docker like this:
version: '3.5'
services:
RedisServerA:
container_name: RedisServerA
image: redis:3.2.11
command: "redis-server --port 26379"
volumes:
- ../docker/redis/RedisServerA:/data
ports:
- 26379:26379
expose:
- 26379
RedisServerB:
container_name: RedisServerB
image: redis:3.2.11
command: "redis-server --port 6379"
volumes:
- ../docker/redis/RedisServerB:/data
ports:
- 6379:6379
expose:
- 6379
Now I do a vagrant ssh and do
ping RedisServerA
ping RedisServerB
They both work.
Now I try to connect to the redis server:
redis-cli -h RedisServerB
Works fine
Then I try to connect to the other
redis-cli -h RedisServerA -p 26739
It says:
Could not connect to Redis at RedisServerA:26739: Connection refused
Could not connect to Redis at RedisServerA:26739: Connection refused
Twice.
What am I missing here?

Answer 1

Typically in this setup you'd let each container run on its "natural" port. For connections from outside Docker you need the ports: mapping, and you'd access a container via its published port on the host's IP address. For connections between Docker containers (assuming they're on the same network, and if you used bare docker run, you manually created that network), you use the container name and the container's internal port number.
We can clean up the docker-compose.yml file by removing some unnecessary lines (container_name: and expose: don't really have a practical effect) and letting the image run its default command: on the default port, and only remapping with ports:. We'd get:
version: '3.5'
services:
RedisServerA:
image: redis:3.2.11
volumes:
- ../docker/redis/RedisServerA:/data
ports:
- 26379:6379
RedisServerB:
image: redis:3.2.11
volumes:
- ../docker/redis/RedisServerB:/data
ports:
- 6379:6379
Between containers, you'd use the default port
redis-cli -h RedisServerA
redis-cli -h RedisServerB
From outside Docker you'd use the server's host name and the published ports
redis-cli -h server.example.com -p 23679
redis-cli -h server.example.com