How to use act with a workflow that needs access to a local database?

[centranoisacs]

My CI workflow runs integration tests that need a PostgreSQL database. On GitHub Actions this works with the services: block:

services:
  postgres:
    image: postgres:16
    ports:
      - 5432:5432

When I run this locally with act push, the service container starts but my test container can't connect to it. localhost:5432 doesn't resolve from inside the job container.

I tried --network host but that broke other things. Also tried using the service label as hostname (postgres:5432) like you would on GitHub Actions but that doesn't work either.

What's the right way to handle service containers with act? Do I need to set up a Docker network manually?

[mehvetero]

the service container hostname works on real github actions because they set up a docker network + DNS alias automatically. act doesn't do that by default.

what works for me:

1. skip the service container and run postgres yourself:

docker run -d --name pg -p 5432:5432 -e POSTGRES_PASSWORD=test postgres:16
act push --env DATABASE_URL=postgresql://postgres:test@host.docker.internal:5432/test

host.docker.internal resolves from inside the job container on docker desktop. on linux you might need --add-host=host.docker.internal:host-gateway.

2. or if you want to keep the service container in your workflow, pass --network host to act and change your test config to connect to localhost:5432 instead of postgres:5432.

option 1 is more reliable. the built-in service container support in act has always been flaky with networking.