node.js - ECONNREFUSED for Postgres on nodeJS with dockers

Question

I'm building an app running on NodeJS using postgresql. I'm using SequelizeJS as ORM. To avoid using real postgres daemon and having nodejs on my own device, i'm using containers with docker-compose.

when I run docker-compose up it starts the pg database

database system is ready to accept connections

and the nodejs server. but the server can't connect to database.

Error: connect ECONNREFUSED 127.0.01:5432

If I try to run the server without using containers (with real nodejs and postgresd on my machine) it works.

But I want it to work correctly with containers. I don't understand what i'm doing wrong.

here is the docker-compose.yml file

web:
  image: node
  command: npm start
  ports:
    - "8000:4242"
  links:
    - db
  working_dir: /src
  environment:
    SEQ_DB: mydatabase
    SEQ_USER: username
    SEQ_PW: pgpassword
    PORT: 4242
    DATABASE_URL: postgres://username:pgpassword@127.0.0.1:5432/mydatabase
  volumes:
    - ./:/src
db:
  image: postgres
  ports:
  - "5432:5432"
  environment:
    POSTGRES_USER: username
    POSTGRES_PASSWORD: pgpassword

Could someone help me please?

(someone who likes docker :) )

Answer 1

Your DATABASE_URL refers to 127.0.0.1, which is the loopback adapter (more here). This means "connect to myself".

When running both applications (without using Docker) on the same host, they are both addressable on the same adapter (also known as localhost).

When running both applications in containers they are not both on localhost as before. Instead you need to point the web container to the db container's IP address on the docker0 adapter - which docker-compose sets for you.

Change:

127.0.0.1 to CONTAINER_NAME (e.g. db)

Example:

DATABASE_URL: postgres://username:pgpassword@127.0.0.1:5432/mydatabase

to

DATABASE_URL: postgres://username:pgpassword@db:5432/mydatabase

This works thanks to Docker links: the web container has a file (/etc/hosts) with a db entry pointing to the IP that the db container is on. This is the first place a system (in this case, the container) will look when trying to resolve hostnames.