TLDR: Do not put any double quotes or single quotes into the environment parameter in the docker-compose.yml file. Do we really need the long version of the story?
Instead of this:
version: '3.2'
services:
mongo:
image: mongo:4.1.13-bionic
environment:
- MONGO_DATABASE=market-inventory
ports:
- "27017:27017"
networks:
- service-local
web:
build: .
expose:
- "3000"
ports:
- "3000:3000"
environment:
- MONGO_URL="mongodb://mongo/market-inventory"
depends_on:
- mongo
networks:
- service-local
networks:
service-local:
driver: bridge
Use this instead:
version: '3.2'
services:
mongo:
image: mongo:4.1.13-bionic
environment:
- MONGO_DATABASE=market-inventory
ports:
- "27017:27017"
networks:
- service-local
web:
build: .
expose:
- "3000"
ports:
- "3000:3000"
environment:
- MONGO_URL=mongodb://mongo/market-inventory
depends_on:
- mongo
networks:
- service-local
networks:
service-local:
driver: bridge
Now this is odd as I don’t present the problem first. I usually starts with a problem, then the solution. So my problem was that my app is not able to connect to my MongoDB server due to some connection refused error. I tried to debug it by logging in into the container and pinged the MongoDB server and it actually responded.
It turns out that my NestJS app captured the environment variable MONGO_URL with double quotes after I tried to log it. I just removed the double quotes and it already works. Now, there is actually an alternative syntax that will prevent that issue.
environment:
MONGO_INITDB_ROOT_USERNAME: root
MONGO_INITDB_ROOT_PASSWORD: example
However, I didn’t changed my config anymore. Maybe later. Maybe never. Will find out.