How to setup psycopg2 in a docker container running on a droplet?

I’m trying to wrap a scraping project in a Docker container to run it on a droplet. The spider scraps a website and then writes the data to a postgres database. The postgres database is already running and managed by Digitalocean.

When I run the command locally to test, everything is fine:

docker compose up

I can visualize the spider writing on the database.

Then, I use github action to build and push my docker image on a registry each time I push the code with the script:

name: CI

# 1
# Controls when the workflow will run.
on:
  # Triggers the workflow on push events but only for the master branch
  push:
    branches: [ master ]

  # Allows you to run this workflow manually from the Actions tab
  workflow_dispatch:
    inputs:
      version:
        description: 'Image version'
        required: true
#2
env:
  REGISTRY: "registry.digitalocean.com/*****-registery"
  IMAGE_NAME: "******-scraper"
  POSTGRES_USERNAME: ${{ secrets.POSTGRES_USERNAME }}
  POSTGRES_PASSWORD: ${{ secrets.POSTGRES_PASSWORD }}
  POSTGRES_HOSTNAME: ${{ secrets.POSTGRES_HOSTNAME }}
  POSTGRES_PORT: ${{ secrets.POSTGRES_PORT }}
  POSTGRES_DATABASE: ${{ secrets.POSTGRES_DATABASE }}
  SPLASH_URL: ${{ secrets.SPLASH_URL }}

#3
jobs:
  build-compose:
    name: Build docker-compose
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2

    - name: Insall doctl
      uses: digitalocean/action-doctl@v2
      with:
        token: ${{ secrets.DIGITALOCEAN_ACCESS_TOKEN }}

    - name: Login to DO Container Registry with short-lived creds
      run: doctl registry login --expiry-seconds 1200

    - name: Remove all old images
      run: if [ ! -z "$(doctl registry repository list | grep "****-scraper")" ]; then doctl registry repository delete-manifest ****-scraper $(doctl registry repository list-tags ****-scraper | grep -o "sha.*") --force; else echo "No repository"; fi

    - name: Build compose
      run: docker compose -f docker-compose.yaml up -d

    - name: Push to Digital Ocean registery
      run: docker compose push

  deploy:
    name: Deploy from registery to droplet
    runs-on: ubuntu-latest
    needs: build-compose

Then I ssh root@ipv4 manually to my droplet in order to install docker, docker compose and run the image from the registry with:

# Login to registry
docker login -u DO_TOKEN -p DO_TOKEN registry.digitalocean.com
# Stop running container
docker stop ****-scraper
# Remove old container
docker rm ****-scraper
# Run a new container from a new image
docker run -d --restart always --name ****-scraper registry.digitalocean.com/****-registery/****-scraper

As soon as the python script starts on the droplet I have the error:

psycopg2.OperationalError: could not connect to server: No such file
or directory Is the server running locally and accepting connections
on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

It seems like I’m doing something wrong and I can’t find how to fix this so far.
I would appreciate some help explanations.

Thanks,

My Dockerfile:

# As Scrapy runs on Python, I run the official Python 3 Docker image.
FROM python:3.9.7-slim

# Set the working directory to /usr/src/app.
WORKDIR /usr/src/app

# Install libpq-dev for psycopg2 python package
RUN apt-get update 
    && apt-get -y install libpq-dev gcc

# Copy the file from the local host to the filesystem of the container at the working directory.
COPY requirements.txt ./

# Install Scrapy specified in requirements.txt.
RUN pip3 install --no-cache-dir -r requirements.txt

# Copy the project source code from the local host to the filesystem of the container at the working directory.
COPY . .

# For Slash
EXPOSE 8050

# Run the crawler when the container launches.
CMD [ "python3", "./****/launch_spiders.py" ]

My docker-compose.yaml

version: "3"

services:
  splash:
    image: scrapinghub/splash
    restart: always
    command: --maxrss 2048 --max-timeout 3600 --disable-lua-sandbox --verbosity 1
    ports:
      - "8050:8050"
  launch_spiders:
    restart: always
    build: .
    volumes:
      - .:/usr/src/app
    image: registry.digitalocean.com/****-registery/****-scraper
    depends_on:
      - splash