Docker Compose Postgres Container connection refused from hosting machine

Question

I have the following definition of docker-compose file with postgres image that I want to run and connect to it from hosting machine of my PC, but I'm getting Connection Refused localhost:5432 all the time. I realize that container has to be run on host network driver, but network mode doesn't solve this problem. What I'm doing wrong?

I run this with docker-compose -f [file] up on Windows 10 with Docker for Desktop

version: '3.7'
services:
  database:
      image: postgres:10.6
      restart: always
      ports:
        - "5432:5432"
      environment:
        - POSTGRES_USER=postgres
        - POSTGRES_PASSWORD=p0stgr@s
        - POSTGRES_DB=eagle_eye_local
      network_mode: host

When I run the same container with the following command it works:

docker container run --name postgres10.6 -e POSTGRES_PASSWORD=p0stgr@s -e POSTGRES_USER=postgres -e  POSTGRES_DB=eagle_eye_local -p 5432:5432 postgres:10.6

Answer 1

I'm assuming you are not running natively on linux but use some Docker for Desktop. Then the short answer is: Remove the network_mode: host and the compose setup will work the same way your docker run command works.

version: '3.7'
services:
  database:
      image: postgres:10.6
      restart: always
      ports:
        - "5432:5432"
      environment:
        - POSTGRES_USER=postgres
        - POSTGRES_PASSWORD=p0stgr@s
        - POSTGRES_DB=eagle_eye_local

The two examples you provided are not really equal even though they can lead to some similar results when run on a real linux host (similar in a way that on a linux host you will be able to access the postgres instance via localhost:5432 on the host machine).

If you run the given compose file on Docker for Desktop (Mac or Windows) you must keep in mind that in this case there is a VM running your containers and all commands are passed into that VM. If you don't use network_mode: host Docker will (1) expose the port correctly on the VM and (2) have some proxy process in place on your host machine (mac/windows) to forward the traffic into the VM. This basically doesn't work when you start the container with network_mode: host.

You can verify the established mapping when running docker ps under the Ports column. This will be empty if you run with network_mode: host.

For some more details see the discussions in the docker forum.