Docker Compose cannot connect to database - docker

Question

I'm using nestjs for my backend and using typeorm as ORM.
I tried to define my database and my application in an docker-compose file.
If I'm running my database as a container and my application from my local machine it works well. My program connects and creates the tables etc.
But if I try to connect the database from within my container or to start the container with docker-compose up it fails.
Always get an ECONNREFUSED Error.
Where is my mistake ?
docker-compose.yml
version: '3.1'
volumes:
dbdata:
services:
db:
image: postgres:10
volumes:
- ./dbData/:/var/lib/postgresql/data
restart: always
environment:
- POSTGRES_PASSWORD=${TYPEORM_PASSWORD}
- POSTGRES_USER=${TYPEORM_USERNAME}
- POSTGRES_DB=${TYPEORM_DATABASE}
ports:
- ${TYPEORM_PORT}:5432
backend:
build: .
ports:
- "3001:3000"
command: npm run start
volumes:
- .:/src
Dockerfile
FROM node:10.5
WORKDIR /home
# Bundle app source
COPY . /home
# Install app dependencies
#RUN npm install -g nodemon
# If you are building your code for production
# RUN npm install --only=production
RUN npm i -g #nestjs/cli
RUN npm install
EXPOSE 3000
.env
# .env
HOST=localhost
PORT=3000
NODE_ENV=development
LOG_LEVEL=debug
TYPEORM_CONNECTION=postgres
TYPEORM_HOST=localhost
TYPEORM_USERNAME=postgres
TYPEORM_PASSWORD=postgres
TYPEORM_DATABASE=mariokart
TYPEORM_PORT=5432
TYPEORM_SYNCHRONIZE=true
TYPEORM_DROP_SCHEMA=true
TYPEORM_LOGGING=all
TYPEORM_ENTITIES=src/database/entity/*.ts
TYPEORM_MIGRATIONS=src/database/migrations/**/*.ts
TYPEORM_SUBSCRIBERS=src/database/subscribers/**/*.ts
I tried to use links but it don't work in the container.

Answer 1

Take a look at your /etc/hosts inside the backend container. You will see
192.0.18.1 dir_db_1
or something like that. The IP will be different and dir will represent the dir you're in. Therefore, you must change TYPEORM_HOST=localhost to TYPEORM_HOST=dir_db_1.
Although, I suggest you set static names to your containers.
services:
db:
container_name: project_db
...
backend:
container_name: project_backend
In this case you can always be sure, that your container will have a static name and you can set TYPEORM_HOST=project_db and never worry about the name ever again.

Answer 2

You can create a network and share among two services.
Create network for db and backend services:
networks:
common-net: {}
and add the network to these two services. So your .yml file would like below after edit:
version: '3.1'
volumes:
dbdata:
services:
db:
image: postgres:10
volumes:
- ./dbData/:/var/lib/postgresql/data
restart: always
environment:
- POSTGRES_PASSWORD=${TYPEORM_PASSWORD}
- POSTGRES_USER=${TYPEORM_USERNAME}
- POSTGRES_DB=${TYPEORM_DATABASE}
ports:
- ${TYPEORM_PORT}:5432
networks:
- common-net
backend:
build: .
ports:
- "3001:3000"
command: npm run start
volumes:
- .:/src
networks:
- common-net
networks:
common-net: {}
Note1: After this change, there is no need to expose the Postgres port externally unless you have a reason for it. You can remove that section.
Note2: TYPEORM_HOST should be renamed to db. Docker would resolve the IP address of db service by itself.