Running commands on docker container from the host - node.js

Question

Code first, it will be easier to explain what I'm after.
docker-compose.yml
version: '3.4'
services:
db:
user: '${UID}:${GID}'
image: postgres
container_name: postgres
ports:
- '5432:5432'
restart: always
environment:
POSTGRES_HOST: db
POSTGRES_USER: root
POSTGRES_PASSWORD: secret
POSTGRES_DATABASE: foo
PGDATA: /var/lib/postgresql/data/db
volumes:
- ./db/data:/var/lib/postgresql/data/db
- db-init.sh:/docker-entrypoint-initdb.d/:ro
cache:
image: redis:alpine
container_name: redis
sysctls:
net.core.somaxconn: '511'
ports:
- '6379:6379'
command: ['--requirepass "secret"']
api:
image: node:alpine
container_name: api
working_dir: /var/www/app
command: sh -c "npm start"
ports:
- '5000:5000'
volumes:
- node_modules:/var/www/app/node_modules
- .:/var/www/app
env_file: .env
depends_on:
- db
- cache
volumes:
node_modules:
postgres connection settings for node.js app:
export const {
POSTGRES_USER = 'root',
POSTGRES_PASSWORD = 'secret',
POSTGRES_HOST = 'db',
POSTGRES_PORT = 5432,
POSTGRES_DATABASE = 'foo',
} = process.env
issue:
When using service or container name (db or postgres) for the POSTGRES_HOST setting of node app:
I can successfully connect to, and query, the database.
I'm not able to run commands from host which affect the container. For example, seeding db won't work:
npx knex --esm seed:run
This makes sense, as the DNS resolution for db / postgres is taken care of by docker and those only have meaning on the network connecting the containers. Commands run from the host and targeting that container will fail as host doesn't know how to resolve the DNS here.
On the other hand, when using localhost for the POSTGRES_HOST setting of node app:
Queries to postgres from api will fail.
Commands run from the host, like npx knex --esm seed:run, will succeed.
Again, this makes perfect sense. Addressing container as localhost from host will work thanks to the port forwarding in docker-compose.yml. But in the context of the container, it refers to that very container: for api localhost means itself, and its trying to find a database on localhost:5432 or api:5432.
I want to have working inter-container network and also run commands from the host, addressing the said containers. I'm aware of two approaches to achieve that:
Use container / service name as POSTGRES_HOST, and run commands against the containers with:
docker exec -it <container_name> <command>
Assign static ips to the containers and use those instead of service / container names.
Do I have any other options here?

Answer 1

since you are exposing the database ports on the host machine you can do the following.
Use service or container name (db or postgres) for the POSTGRES_HOST, this way it will work for Docker containers.
when you run the seed command form the host, overwrite the POSTGRES_HOST. This can be done in this way
$ export POSTGRES_HOST=127.0.0.1
$ npx knex --esm seed:run
or in one step
$ POSTGRES_HOST=127.0.0.1 npx knex --esm seed:run