CI/CD with Docker - what is the final deployment step?

Question

I am developing a small website (Ruby/Sinatra) to be used internally where I work. (Simply, it crunches some source data and generates reports.)

I'm want to deploy it using Docker and have a set up that works on my dev environment, but I'm trying to understand the workflow for "production" deployment (we're using Jenkins).

I've read lots of articles about deployment workflows using Docker, but they all seem to stop at "and then push your image to the Docker registry". What seems to be missing is how to then take that image and actually update the application.

I appreciate that every application is likely to be different, but what is the next step? I'm aware of lots of different frameworks like Chef, Puppet, Ansible that could be used, but my question really is - how do I integrate that into my CI/CD pipeline? E.g. does a job "push" the changes to the production server, or should a Jenkins slave be running on the production server to execute a job directly on the server?

Answer 1

It depends on how your application is configured to run. In my case, I have a call to "docker run" in a systemd script. It's configured to just restart if it ever stops.

So, in my Jenkinsfile, after I push the image to the registry, I do a "docker pull" (my Jenkins agent is running on the same box that the application is running on), and then a "docker stop". That causes the application to exit, then restarts, which causes it to get the new version that was just pulled, and now it's running the new version.

Answer 2

There are several orchestration tools like docker-swarm, kubernetes and rancher. In docker swarm for example you create services and can update the versions in blue-green deployment manner also for just one instance (then there is no blue-green :) ) and if you just use docker run you should check your running container, stop and remove it if its running an start your docker container with the newer image version.