Zero downtime docker, with docker-compose and nginx

deploy.sh

 --> script pull or build image

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

zero_downtime_deploy() {
  service_name=name_of_service_docker_compose
  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)

  echo $new_container_ip

  sleep 5


## Curl new container if the response is 200 so deploy new container
  if [[ $(curl -o /dev/null -s -w "%{http_code}\n" --max-time 3 http://$new_container_ip:5000) = 200 ]];
     then
        # 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
     else
        docker-compose up -d --no-deps --scale $service_name=1 --no-recreate $service_name
        
        echo "Gagal deploy, CHECK RUNNING CONTAINER"
  fi

}

zero_downtime_deploy

docker-compose.yaml.example

version: '3.8'

services:
  backend:
    image: nginx-test
    build: .
    restart: always

  reverse-proxy:
    container_name: nginx-lb
    image: nginx
    volumes:
      - ./default.conf:/etc/nginx/conf.d/default.conf
    ports:
      - 80:80

Dockerfile.example

FROM nginx:alpine
COPY index.html /usr/share/nginx/html

index.html

Test zero downtime