Blue/green zero-downtime deployments using Traefik

This is a demo repo exploring how to support blue/green deployments with zero downtime using Traefik. It's based on Max Countryman's blog post.

It's not intended for production use right away - the Traefik dashboard and API are unsecured and there's no TLS.

Start the Traefik reverse proxy:

docker compose --c=traefik --file docker-compose.traefik.yml up --detach

Access the Traefik dashboard at http://localhost:8080/dashboard

Run the ./deploy deployment script:

Starting blue-web container
[+] Running 1/1
 ✔ Container blue-web  Started                                                                                                                                                                   0.1s
Waiting for blue-web to become healthy...
blue-web is healthy
Checking if Traefik recognizes blue-web...
Traefik recognizes blue-web as healthy

A sample web app should deploy and become accessible at http://localhost.

Run docker ps and you should see the blue-web container running:

CONTAINER ID   IMAGE                     COMMAND                  CREATED          STATUS              PORTS                                          NAMES
d9ba1d66fc75   nginxdemos/hello:latest   "/docker-entrypoint.…"   59 seconds ago   Up 59 seconds       80/tcp                                         blue-web
0270e2e71273   traefik:v2.9              "/entrypoint.sh trae…"   36 minutes ago   Up About a minute   0.0.0.0:80->80/tcp, 127.0.0.1:8080->8080/tcp   traefik

Run the deployment script again to simulate a new version.

Now docker ps shows that the green container is running and the blue container has been stopped:

CONTAINER ID   IMAGE                     COMMAND                  CREATED          STATUS          PORTS                                          NAMES
95881a3001b1   nginxdemos/hello:latest   "/docker-entrypoint.…"   39 seconds ago   Up 38 seconds   80/tcp                                         green-web
0270e2e71273   traefik:v2.9              "/entrypoint.sh trae…"   37 minutes ago   Up 2 minutes    0.0.0.0:80->80/tcp, 127.0.0.1:8080->8080/tcp   traefik