Docker deployment - one machine - no downtime

Question

I have only one small web project to be run through the Docker and only one machine where I can't use virtualization and I don't really need that either. I would like to know how can I deploy my application to VPS with Docker without any downtime.

For now, I am just using a repository and creating docker container with docker-compose (including some configuration for production through specific .yaml file).

I guess the best would be to use Swarm, but I think it's not possible since I could only use one machine.

Answer 1

Here's a simple approach we’ve used in production with just nginx and docker-compose: https://engineering.tines.com/blog/simple-zero-downtime-deploys

Basically, it’s this bash script:

reload_nginx() {  
  docker exec nginx /usr/sbin/nginx -s reload  
}

zero_downtime_deploy() {  
  service_name=tines-app  
  old_container_id=$(docker ps -f name=$service_name -q | tail -n1)

  # bring a new container online, running new code  
  # (nginx continues routing to the old container only)  
  docker-compose up -d --no-deps --scale $service_name=2 --no-recreate $service_name

  # wait for new container to be available  
  new_container_id=$(docker ps -f name=$service_name -q | head -n1)
  new_container_ip=$(docker inspect -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $new_container_id)
  curl --silent --include --retry-connrefused --retry 30 --retry-delay 1 --fail http://$new_container_ip:3000/ || exit 1

  # start routing requests to the new container (as well as the old)  
  reload_nginx

  # take the old container offline  
  docker stop $old_container_id
  docker rm $old_container_id

  docker-compose up -d --no-deps --scale $service_name=1 --no-recreate $service_name

  # stop routing requests to the old container  
  reload_nginx  
}

Answer 2

Single machine deployments are a great use case for Swarm. You can do "rolling updates" if your services that make it possible for zero downtime service updates (assuming your running 2 containers of a service).

Obviously, you won't have hardware or OS level fault-tolerance, but Swarm is a better solution for production then the docker-compose cli.

See all my reasons for using Swarm in this case in my GitHub AMA on the subject: Only one host for production environment. What to use: docker-compose or single node swarm?

See my YouTube video on an example of rolling updates.