phaniamt / docker-swarm

docker-swarm deployment with zero downtime

Create a docker-compose file for nginx stack and deploy it

version: '3.7'
networks:
  nginx:
    external: false
services:
  nginx:
    image: nginx:1.18
    ports:
      - '8088:80'
    deploy:
      replicas: 4
      update_config:
        parallelism: 2
        order: start-first
        failure_action: rollback
        delay: 10s
      rollback_config:
        parallelism: 0
        order: stop-first
      restart_policy:
        condition: any
        delay: 5s
        max_attempts: 3
        window: 120s
    healthcheck:
      test: ["CMD", "service", "nginx", "status"]
    networks:
      - nginx

Deploy the docker stack

docker stack deploy -c docker-compose.yml nginx

List the docker stacks

docker stack ls

List the docker services

docker service ls

List the running docker containers

docker ps

Update the docker image tag in the docker-compose file

version: '3.7'
networks:
  nginx:
    external: false
services:
  nginx:
    image: nginx:1.19
    ports:
      - '8088:80'
    deploy:
      replicas: 4
      update_config:
        parallelism: 2
        order: start-first
        failure_action: rollback
        delay: 10s
      rollback_config:
        parallelism: 0
        order: stop-first
      restart_policy:
        condition: any
        delay: 5s
        max_attempts: 3
        window: 120s
    healthcheck:
      test: ["CMD", "service", "nginx", "status"]
    networks:
      - nginx

Update the docker stack

docker stack deploy -c docker-compose.yml nginx

List the docker stacks

docker stack ls

List the docker services

docker service ls

List the running docker containers

docker ps

Ref Links

https://medium.com/better-programming/zero-downtime-deployment-with-docker-swarm-d84d8d9d9a14 https://docs.docker.com/compose/compose-file/#update_config

Docker swarm health check

version: '3.7'

networks:
  nginx:
    external: false

services:

# --- NGINX ---
  nginx:
    image: nginx:1.19
    ports:
      - '8088:80'
    deploy:
      replicas: 4
      update_config:
        parallelism: 2
        order: start-first
        failure_action: rollback
        delay: 10s
      rollback_config:
        parallelism: 0
        order: stop-first
      restart_policy:
        condition: any
        delay: 5s
        max_attempts: 3
        window: 120s
    healthcheck:
      test: curl --fail -s http://localhost:80/ || exit 1
      interval: 5s
      timeout: 3s
      retries: 3
      start_period: 10s
    networks:
      - nginx

Test the health check

Login inside the any one of the container

docker ps
docker exec -it containerid bash

Move index.html to /tmp so that health check command will get 400 status code and will become unhealthly

mv  /usr/share/nginx/html/index.html /tmp/

check the conatiners again . if health check fails , Docker swarm will kill that container and create the new container

docker service ps
docker ps