How to rebuild and update a container without downtime with docker-compose?

Question

I enjoy a lot using docker-compose.

Eg. on my server, when I want to update my app with minor changes, I only need to git pull origin master && docker-comp

Answer 1

The problem is that restart will restart your current containers, which is not what you want.

As an example, I just did this

• change the docker file for one of the images
• call docker-compose build to build the images
• call docker-compose down¹ and docker-compose up
  • docker-compose restart will NOT work here
  • using docker-compose start instead also does not work

To be honest, i'm not completly sure you need to do a down first, but that should be easy to check.¹ The bottomline is that you need to call up. You will see the containers of unchanged images restarting, but for the changed image you'll see recreating.

The advantage of this over just calling up --build is that you can see the building-process first before you restart.

1: from the comments; down is not needed, you can just call up --build. Down has some "down"-sides, including possible being destructive to your (volume-)data.

Answer 2

You can use Swarm. Init swarm first by docker swarm init command and use healthcheck in docker-compose.yml.

Then run below command:

docker stack deploy -c docker-compose.yml project_name

instead of

docker-compose up -d.

When docker-compose.yml file is updated only run this command again:

docker stack deploy -c docker-compose.yml project_name

Docker Swarm will create new version of services and stop old version after that.