How to update rails app on production with Docker and Fig with zero downtime?

Question

I am using Docker and Fig for my Rails/Postgres app.

What is the best way to push updates to Rails app to production? Currently I am running the following script on production but it causes about 10 seconds of downtime:

sudo fig pull web
sudo fig up -d web

I guess the downtime happens when Fig recreates the web container.

Here is a fig.xml file I use on production.

db:
  image: postgres:9.3
  volumes_from:
    - db-data
  ports:
    - 5432
web:
  image: myaccount/my_private_repo
  command: bundle exec unicorn -p 3000 -c ./config/unicorn.rb
  volumes_from:
    - gems-2.1
  ports:
    - "80:3000"
  links:
    - db

The demo of the app is here: https://github.com/evgenyneu/docker-rails-fig-sample

Answer 1

The normal way to approach this is to run the app on multiple servers behind a load balancer. Do a rolling upgrade where one server at a time is stopped, new version pulled, and new version runs so as to preserve uptime.