docker-compose, run a script after container has started?

This is the way I use for calling a script after a container is started without overriding the entrypoint.

In my example, I used it for initializing the replicaset of my local MongoDB

services:
  mongo:
    image: mongo:4.2.8
    hostname: mongo
    container_name: mongodb
    entrypoint: ["/usr/bin/mongod","--bind_ip_all","--replSet","rs0"]
    ports:
      - 27017:27017
  mongosetup:
    image: mongo:4.2.8
    depends_on:
      - mongo
    restart: "no"
    entrypoint: [ "bash", "-c", "sleep 10 && mongo --host mongo:27017 --eval 'rs.initiate()'"]      

• In the first part, I simply launch my service (mongo)
• The second service use a “bash” entry point AND a restart: no <= important

I also use a depends_on between service and setup service for manage the launch order.