Github Actions db service container not reachable - docker

Question

I have the following Github Actions pipeline:
name: Elixir CI
on:
push:
branches:
- '*'
pull_request:
branches:
- '*'
jobs:
build:
name: Build and test
runs-on: ubuntu-latest
services:
postgres:
image: postgres
env:
POSTGRES_USER: postgres
POSTGRES_PASSWORD: password
POSTGRES_PORT: 5432
options: >-
--health-cmd pg_isready
--health-interval 10s
--health-timeout 5s
--health-retries 5
ports:
- 5432:5432
steps:
- uses: actions/checkout#v2
- name: Docker Setup Buildx
uses: docker/setup-buildx-action#v1.6.0
with:
install: true
- name: building image
env:
DATABASE_HOST: postgres
DATABASE_PORT: 5432
run: |
docker build --build-arg DATABASE_HOST=$DATABASE_HOST -t backend:test -f Dockerfile.ci .
I have a single build step for an Elixir app: the dockerfile is a multistage one, the first stage runs the tests and builds the production app, and the second copies the application folder/tar.
DATABASE_HOST is the variable that my Elixir app looks for to connect to the test environment.
I have the need to run tests against Postgres, so I spawn a container service with it. I have executed the build both in a container and outside of it, but I always have the following error:
...
#19 195.9 14:10:58.624 [error] GenServer #PID<0.9316.0> terminating
#19 195.9 ** (DBConnection.ConnectionError) tcp connect (postgres:5432): non-existing domain - :nxdomain
#19 195.9 (db_connection 2.4.1) lib/db_connection/connection.ex:100: DBConnection.Connection.connect/2
#19 195.9 (connection 1.1.0) lib/connection.ex:622: Connection.enter_connect/5
#19 195.9 (stdlib 3.14.2.2) proc_lib.erl:226: :proc_lib.init_p_do_apply/3
#19 195.9 Last message: nil
...
So apparently postgres:5432 is not reachable, am I missing something ?

Answer 1

The problem is in DATABASE_HOST: postgres I think.
The service container exports 5432 port to host, so for docker build, it should use host's ip address to visit that postgres service like next:
- name: building image
env:
DATABASE_PORT: 5432
run: |
DATABASE_HOST=$(ifconfig -a eth0|grep inet|grep -v 127.0.0.1|grep -v inet6|awk '{print $2}'|tr -d "addr:")
docker build --build-arg DATABASE_HOST=$DATABASE_HOST -t backend:test -f Dockerfile.ci .
Above will first use ifconfig to get virtual machine's ip(docker host's ip), then pass to docker build to let build container to visit the postgres.