docker-compizo

Deploys a new version of Docker Compose service without downtime.

This project is an Elixir port of docker-rollout with minor improvements.

Requirements

• Elixir 1.14 or later
• Docker with docker compose support.

Usage

First, write the compose.yaml for your application.

Then, run:

$ docker-compizo -f compose.yaml <service>

Above command will:

1. deploy all other services except <service>.
2. deploy <service>:
   • if the <service> is not running, <service> will be deployed directly.
   • if the <service> is running, and when one of the following conditions is met, <service> will be deployed carefully, without downtime:
     • if the compose config hash of <service> is changed.
     • if the replicas of <service> is changed.
   • in other cases, nothing will be deployed.

See docker-compizo --help and examples in examples directory for more usage.

Limits

• A proxy is required to route traffic. Traefik is recommended.
• Services scaled by docker-compizo cannot have container_name and ports defined in compose.yaml, as it's not possible to run multiple containers with the same name or port mapping.
• Each deployment will increase the index of container names. For example, project-service-1 will be project-service-2.

Guidelines

• It's better to provide healthcheck to containers. In conjunction with healthchecks, it is easier to only route traffic to the new containers when they're ready.

How it works?

docker-compizo achieves zero downtime deployment by a simple blue/green strategy:

1. scaling the service for more containers
2. waiting for the new containers to be ready
3. removing the old containers

Why?

Using container orchestration tools like Kubernetes, Nomad or vice versa is usually an overkill for most projects.

I prefer the simple solution - Docker Compose. But, using docker compose up to deploy a new version of a service causes downtime because the containers are stopped before the new containers are created. Nowadays, this kind of downtime is unacceptable for end users.

docker-compizo tries to maintain a balance between a simple solution and a good end-user experience.

About the name

Compizo (/kəmˈpaɪzoʊ/) is a compound word formed by combining compose and and zero deployment:

docker-compizo = docker-compose + zero deployment

TODO

• Rewrite this project with Docker engine API.
• Integrate with a default proxy, such as docker-easy-haproxy.
• Support connection draining.

License

MIT