Multiple issues with document "Migrate from Docker Compose to Aspire"

[dimabarbul]

Document docs/get-started/migrate-from-docker-compose.md contains multiple issues when providing comparison of docker-compose and Aspire approaches.

Issues with Aspire Equivalent Code

1. Section "Multi-service web application":

• frontend and api services are used as docker cotnainers which have images built before docker-compose is started whereas Aspire does not build and use projects
• frontend and api services do not have ports described: in docker-compose they are mapped to static host port, in Aspire they are not
• frontend depends on api, i.e., is not started before api is ready, in Aspire they are started in parallel
• postgres does not have image specified, it is defined by package providing postgres integration and is not guaranteed to be the same as in docker-compose
• postgres username and password are not set
• postgres does not have volume attached
• frontend expects environment variable API_URL, instead it's provided only with services__api__<ENDPOINT_NAME>__0 variable only if api service has launchSettings.json (as the ports are not specified)
• api expects environment variable ConnectionStrings__DefaultConnection, but is provided with ConnectionStrings__myapp instead
• sentence "Service dependencies: depends_on becomes WithReference() which also configures service discovery." is not true: this line only configures service discovery, it has nothing to do with the startup order whereas short docker-compose depends_on syntax makes service wait until its dependency is ready
• sentence "Data persistence: Volumes are automatically managed by Aspire." is not true: postgres integration provides method .WithDataVolume() that will attach volume to correct path, but it's not done automatically - it needs to be called explicitly by client code

2. Section "Container-based services"

• postgres and redis versions are not specified
• postgres volume is not attached
• redis service port is not mapped to static port on machine in Aspire, but rather to random one
• web service image is built, but Aspire uses already built image from somewhere
• depends_on from docker-compose is not translated to .WaitFor() in Aspire

3. Section "Environment variables and configuration"

• in docker-compose we clearly see names and values for DATABASE_URL (='postgresql://user:pass@db:5432/myapp') and REDIS_URL (='redis://cache:6379'), in Aspire URLs are not set at all, instead it provides connection strings ConnectionStrings__cache (='localhost:38145,password=w1Naqt...') and ConnectionStrings__myapp (='Host=localhost;Port=42055;Username=postgres;Password=5qYKA3...;Database=myapp')
  format, username, password, ports - everything is different

4. Section "Custom networks and volumes"

• docker-compose example contains unnecessary network, which can be deleted, it is just mistake in docker-compose and is not benefit of Aspire
  docker-compose example should be corrected and Aspire equivalent should be updated accordingly (or say that Aspire does not support this); example of correct usage of custom networks can be found on docs.docker.com:

  services:
    proxy:
      build: ./proxy
      networks:
        - frontend
    app:
      build: ./app
      networks:
        - frontend
        - backend
    db:
      image: postgres
      networks:
        - backend
  
  networks:
    frontend:
    backend:

• example with external network can be shown (I think, Aspire does not support such scenario)

Other Issues

1. Section "Migration strategy" contains related link to migration from Docker Compose V1 to Docker Compose V2. I'm not sure this is in any way related to the section.

2. Section "Common issues and solutions". Not an issue per se, but it would be good to know how to migrate service which has health check using some command in docker-compose (for custom images or when integration healthcheck is not enough for some reason), e.g.:

   services:
     rabbit:
       image: rabbitmq:4.1.4-management-alpine
       healthcheck:
         test: ["CMD", "rabbitmqctl", "ping"]
         interval: 30s
         timeout: 10s
         retries: 3
         start_period: 10s