Attaching multiple compose clusters to a pre-existing Docker network

docker-compose.client_cluster.yml

# Should be in ./client_cluster/docker-compose.yml
services:
  client_cluster:
    container_name: client_container
    build:
      context: .
      dockerfile: ./Dockerfile
    networks:
      - ctalk

networks:
  ctalk:
    name: cluster_talk
    external: true

docker-compose.server_cluster.yml

# Should be in ./server_cluster/docker-compose.yml
services:
  server_container:
    container_name: server_container
    build:
      context: .
      dockerfile: ./Dockerfile
    ports:
      - 8000:8000
    networks:
      - ctalk

networks:
  ctalk:
    name: cluster_talk
    external: true

Dockerfile.client_cluster

# Should be in ./client_cluster/Dockerfile
FROM python:3.9-bullseye

ADD ./entrypoint.sh /entrypoint.sh

ENTRYPOINT ["/entrypoint.sh"]

Dockerfile.server_cluster

# Should be in ./server_cluster/Dockerfile
FROM python:3.9-bullseye

RUN mkdir -p /var/www/html \
 && echo "HELLO, WORLD" > /var/www/html/index.html

WORKDIR /var/www/html

ENTRYPOINT ["python3", "-m", "http.server", "8000"]

entrypoint.sh

#!/bin/bash
# Should be in ./client_cluster/entrypoint.sh
sleep 3
for i in 1 2 3 4 5 6 7 8 9; do
    echo "Calling out to the server container:"
    curl -s server_container:8000
    echo "Sleeping 3..."
    sleep 3
done

echo "Got to the last loop iteration, exiting."

main.sh

# Commands to execute to make them talk to each other on a Docker network
docker network create cluster_talk
cd server_cluster
docker-compose up -d
cd ../client_cluster
docker-compose up