Docker application deployment

What I do is tag all my images by version in addition to tagging then "latest". So I have one image with multiple tags. Just tag it with more than one. When you tag by version, it lets you move around the "latest" tag without problems:

docker build -t=myApp .
docker tag myApp:latest myApp:0.8.1

Now when you docker images you'll see the same image listed twice, just with different tags (both "latest" and "0.8.1"). So when you go to build something like you mention:

# the original container is still running while this builds ...
docker build -t=myApp .
# now tag "latest" to the newest version
docker tag myApp:latest myApp:0.8.2
# and now you can just stop and restart the container ...
docker rename myApp myApp-old
docker run -d --name=myApp -p 80:80 myApp:latest

This is something you could do, but it looks like you're really needing a way to swap containers without any downtime. Zero-downtime container changes.

There is a process I have used for a couple of years now of using an Nginx reverse proxy for your Docker containers. Jason Wilder details in this blog post the process for doing so.

I'll give you an overview of what this will do for you. The jwilder/nginx-proxy docker image will serve as a reverse proxy for your containers, and by default it round-robin load-balances inbound connections to containers based on the hostname. After you build and run a container with the same VIRTUAL_HOST environment variable, nginx-proxy automatically round-robin load-balances the two containers. This way, you can start the new container, and it will begin servicing requests. Then you can just bring down your other, old container. Zero-downtime updates.

Just some details: The nginx-proxy image uses Jason Wilder's docker-gen utility to automatically grab the docker container information and then route requests to each. What this means is that you start your normal containers with a new environment variable (VIRTUAL_HOST) and nginx-proxy will automatically begin routing inbound requests to the container. This is best used to "share" a port (e.g. tcp/80) among many containers. Also this reverse proxy means it can handle HTTPS as well as HTTP authentication, so that you don't have to handle it inside your web containers. The backend is unencrypted (HTTP) but since it's on the same host, no problem.