Knexfile not reading environment variables?

Question

I'm building a node/express service using docker and knex for database interaction. I have an env_file (defined in docker-compose file) that has some environment variables defined. The app is reading them correctly, as a console.log(process.env.DATABASE_USER); will log the correct value.

I followed the knex documentation to setup a knexfile that looks like so:

module.exports = {
  development: {
    client: 'pg',
    connection: {
      host: process.env.DATABASE_HOST,
      port: process.env.DATABASE_PORT,
      user: process.env.DATABASE_USER,
      password: process.env.DATABASE_PASSWORD,
      database: process.env.DATABASE_NAME_DEV,
    },
    migrations: {
      directory: __dirname + '/db/migrations',
    },
    seeds: {
      directory: __dirname + '/db/seeds',
    },
  },
};

If I hardcode the values into the knexfile, all is well. I can connect to the database, run migrations, etc.

When I use my environment variables (like above), they return undefined. Why is that?

UPDATE:

My docker compose file--api.env is just a basic .env file:

version: '3.3'

services:
  db:
    container_name: db
    build:
      context: ./services/api/src/db
      dockerfile: Dockerfile
    ports:
      - 5435:5432
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres

  nginx:
    container_name: nginx
    build: ./services/nginx
    restart: always
    ports:
      - 80:80
    depends_on:
      - api
    links:
      - api

  api:
    container_name: api
    build:
      context: ./services/api
      dockerfile: Dockerfile
    volumes:
      - './services/api:/usr/src/app'
      - './services/api/package.json:/usr/src/app/package.json'
    ports:
      - 8887:8888
    env_file: ./api.env
    depends_on:
      - db
    links:
      - db

  client:
    container_name: client
    build:
      context: ./services/client
      dockerfile: Dockerfile
    volumes:
      - './services/client:/usr/src/app'
    ports:
     - 3007:3000
    environment:
      - NODE_ENV=development
    depends_on:
      - api
    links:
      - api

Dockerfile for api service:

FROM node:latest

RUN mkdir /usr/src/app
WORKDIR /usr/src/app

ENV PATH /usr/src/app/node_modules/.bin:$PATH

ADD package.json /usr/src/app/package.json
RUN npm install

CMD ["npm", "start"]

Answer 1

dotenv reads the vars from the files on same level as it is, so if your knexfile is not on the same directory level with you .env, you may want to set the path. Something like this:

import dotenv from 'dotenv'
dotenv.config({ path: '../../.env' })

You can read the docs for more details https://www.npmjs.com/package/dotenv