Cannot connect to Postgres database with Sequelize using docker-compose

Question

I can't manage to authenticate my postgres database. I am using docker-compose. Please find below the relevant files and logs. Is something about my connection string wrong?

docker-compose.yml

version: "3.8"
services:
  app:
    build:
      context: ./
      target: dev
    volumes:
      - .:/src
    command: npm run start:dev
    ports:
      - "3000:3000"
    depends_on:
      - postgres
    environment:
      DATABASE_URL: postgres://votetracker@postgres/codes
      POSTGRES_PASSWORD: password
      NODE_ENV: development
      DEBUG: nodejs-docker-express:*
  postgres:
    image: postgres
    restart: always
    ports:
      - "5432:5432"
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: codes

db.js

const { Sequelize } = require("sequelize");
const sequelize = new Sequelize("postgres://user:pass@database:5432/codes");

const authenticate = async () => {
  try {
    await sequelize.authenticate();
    console.log("Connection has been established successfully.");
  } catch (error) {
    console.error("Unable to connect to the database:", error);
  }
};
module.exports = { authenticate };

When running docker-compose up , this is the output:

postgres_1  | The files belonging to this database system will be owned by user "postgres".
postgres_1  | This user must also own the server process.
...
postgres_1  | Success. You can now start the database server using:
postgres_1  |
postgres_1  |     pg_ctl -D /var/lib/postgresql/data -l logfile start
...
postgres_1  | server started
postgres_1  | CREATE DATABASE
...
postgres_1  | PostgreSQL init process complete; ready for start up.
...
postgres_1  | 2022-01-23 17:32:03.824 UTC [1] LOG:  database system is ready to accept connections
...
app_1       | Your app is running on port 3000
app_1       | Unable to connect to the database: ConnectionError [SequelizeConnectionError]: getaddrinfo EAI_AGAIN database

Answer 1

You're almost there. When you need to connect to another container on a docker-compose bridge network, you use the service name as the hostname.

So instead of

const sequelize = new Sequelize("postgres://user:pass@database:5432/codes");

you need

const sequelize = new Sequelize("postgres://user:pass@postgres:5432/codes");