Zero-downtime deployment script for Docker Compose, Django, and Nginx.

django-compose-rollout.sh

#!/bin/sh
#
# Zero-downtime deployment script for Docker Compose and Nginx (+ Django)
# Inspired by https://www.tines.com/blog/simple-zero-downtime-deploys-with-nginx-and-docker-compose
#
# (c) Romein van Buren 2024
# SPDX-License-Identifier: WTFPL
#

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

zero_downtime_deploy() {
    service_name=app
    old_container_id=$(docker compose ps -q $service_name | 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=$(docker ps -q | head -n1)
    new_container_ip=$(docker inspect -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $new_container_id)
    curl --silent --include --retry-connrefused --retry 30 --retry-delay 1 --fail --header "Host: 0.0.0.0" http://$new_container_ip:8000/ > /dev/null || exit 1

    # Run migrations and collect static assets
    docker exec $new_container_id python manage.py collectstatic --noinput
    docker exec $new_container_id python manage.py migrate

    # 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
}

sudo docker build --no-cache -t app:latest .
zero_downtime_deploy