Docker container names

I'm using Docker on Rails project. I found only one way to reliably link services between each other, i. e. specifying container_name in docker-compose.yml:

docker-compose.yml

version: '3'
services:
db:
container_name: sociaball_db
...
web:
container_name: sociaball_web
...
sphinx:
container_name: sociaball_sphinx
...


So now I can write something like this in database.yml and stop worrying about, say, database container randomly changing its name from db to db_1:

database.yml

db

db_1

common: &common
...
host: sociaball_db


However, I can only run three containers at the same time. Whenever I try to run docker-container up if some containers aren't down it will raise an error.

docker-container up

ERROR: for sociaball_db Cannot create container for service db: Conflict. The container name "/sociaball_db" is already in use by container "ee787c06db7b2a0205e3c1e552b6a5496545a78fe12d942fb792b27f3c38769c". You have to remove (or rename) that container to be able to reuse that name.


It is very inconvenient. It often forces explicitly deleting all the containers just to make sure they have no opportunity to break. Is there a way around that?

container_name:

docker-compose.yml

host: db

1 Answer
1

When running several containers from one compose file, there will be a default network where all containers are attached to (if not specified differently).

There is no need to reference a container by its container or hostname as docker-compose automatically sets up some dns service discovery where each docker-compose service can be resolved by its service name (the key used one level below services:.

services:

So your service called web can reach your database using the name db. No need to specify a container name for this use case. For more details please see the docker docs on networking that also demonstrates a rails app accessing a database.

web

db

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