How do you apply docker to actual projects? If there are 20 cloud servers, one or several Dockers will run on each server. Dockers have web applications inside. If the application is updated, how will it be pushed to these 20 servers?
Web application is applied on github and automatically deployed by jenkins. After updating on github, jenkins starts, pull code to docker image, then push to docker hub, then pull new image on 20 machines, then start new container and close old container.
This is the deployment method for web applications. If docker is a database, it is another matter.