Docker compose, accessing a Postgres container from an other container

Question

I have this really simple setup with a web app in one container and a Postgres service running in another container.

I need to connect to the Postgres container and thought PGHOST="db" would point to that container ..?

But I keep getting Error: getaddrinfo ENOTFOUND "db" at GetAddrInfoReqWrap.onlookup that I read as; can't find the "db" host ...

What am I missing here?

version: "3.9"
services:
  web:
    build: .
    ports:
      - "8081:3011"
    links:
      - db
    environment:
      - PGHOST="db"
      - PGDATABASE="testdb"
      - PGUSER="postgres"
      - PGPASSWORD="postgres"
  db:
    image: postgres
    ports:
      - "5432:5432"
    volumes:
      - /usr/local/var/postgresql@13

Pretty sure this was already answered somewhere else, but you don't need the " around db — Xapadoan
– Xapadoan, Commented Oct 21, 2021 at 14:10
if you want to use quotes you should quote the full string and not just a part of it, but in YAML you don't need quotes most of the time. — The Fool
– The Fool, Commented Oct 21, 2021 at 14:22

Ayzrian · Accepted Answer · 2021-10-21 14:22:52Z

1

Try this config. You don't need quotes when passing env variables. And it is better to use depends_on here to make sure DB is up and running before your app starts.

version: "3.9"
services:
  web:
    build: .
    ports:
      - "8081:3011"
    depends_on:
      - db
    environment:
      - PGHOST=db
      - PGDATABASE=testdb
      - PGUSER=postgres
      - PGPASSWORD=postgres
  db:
    image: postgres
    ports:
      - "5432:5432"
    volumes:
      - /usr/local/var/postgresql@13

edited Oct 21, 2021 at 14:22

answered Oct 21, 2021 at 14:16

Ayzrian

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4 Comments

Xapadoan Over a year ago

You may want to add a depends_on clause for the web service. I'm not sure if the links clause is needed here

Ayzrian Over a year ago

@Hollyol, thanks edited the answer.

The Fool Over a year ago

its better to design the app to work without depends_on with retry logic and things like that.

David Maze Over a year ago

depends_on: doesn't actually ensure the database is up and running; see Docker Compose wait for container X before starting Y. (It does avoid a DNS-lookup error and is generally good practice, though.)

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