Memo Of Docker Swarm

 Reference: https://github.com/docker/labs/blob/master/beginner/chapters/votingapp.md

First, create a Swarm.

$ docker swarm init
Swarm initialized: current node (o9grw63b1jc3kjvxehln2vush) is now a manager.
To add a worker to this swarm, run the following command:
    docker swarm join --token SWMTKN-1-3bxzfkmh9gz4l7ap3qx395br876l6p2uwupeuqhtdws83k8i0y-clyn1usfm5x0jqianoc8j8j7e 192.168.65.3:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

Second, Create a Docker Compose file. names docker-stack.yml

version: "3"
services:

  redis:
    image: redis:alpine
    ports:
      - "6379"
    networks:
      - frontend
    deploy:
      replicas: 1          # deploy only 1 node 
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure
  db:
    image: postgres:9.4
    volumes:
      - db-data:/var/lib/postgresql/data
    networks:
      - backend
    deploy:
      placement:
        constraints: [node.role == manager]
  vote:
    image: dockersamples/examplevotingapp_vote:before
    ports:
      - 5000:80
    networks:
      - frontend
    depends_on:
      - redis
    deploy:
      replicas: 2          # deploy 2 nodes for balance.
      update_config:
        parallelism: 2
      restart_policy:
        condition: on-failure
  result:
    image: dockersamples/examplevotingapp_result:before
    ports:
      - 5001:80
    networks:
      - backend
    depends_on:
      - db
    deploy:
      replicas: 1            # deploy only 1 node 
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure

  worker:
    image: dockersamples/examplevotingapp_worker
    networks:
      - frontend
      - backend
    deploy:
      mode: replicated
      replicas: 1             # deploy only 1 node 
      labels: [APP=VOTING]
      restart_policy:
        condition: on-failure
        delay: 10s
        max_attempts: 3
        window: 120s
      placement:
        constraints: [node.role == manager]

  visualizer:
    image: dockersamples/visualizer
    ports:
      - "8080:8080"
    stop_grace_period: 1m30s
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    deploy:
      placement:
        constraints: [node.role == manager]

networks:
  frontend:
  backend:

volumes:
  db-data:

Third, deploy it, and then we will look more deeply into the details:

docker stack deploy --compose-file docker-stack.yml vote
Creating network vote_frontend
Creating network vote_backend
Creating network vote_default
Creating service vote_vote
Creating service vote_result
Creating service vote_worker
Creating service vote_redis
Creating service vote_db

Fourth, to verify your stack has deployed, use docker stack services vote

$ docker stack services vote
ID            NAME         MODE        REPLICAS  IMAGE
25wo6p7fltyn  vote_db      replicated  1/1       postgres:9.4
2ot4sz0cgvw3  vote_worker  replicated  1/1       dockersamples/examplevotingapp_worker:latest
9faz4wbvxpck  vote_redis   replicated  2/2       redis:alpine
ocm8x2ijtt88  vote_vote    replicated  2/2       dockersamples/examplevotingapp_vote:before
p1dcwi0fkcbb  vote_result  replicated  2/2       dockersamples/examplevotingapp_result:before

If you take a look at docker-stack.yml, you will see that the file defines

• vote container based on a Python image
• result container based on a Node.js image
• redis container based on a redis image, to temporarily store the data.
• .NET based worker app based on a .NET image
• Postgres container based on a postgres image

do vote by http://localhost:5000/

check vote result by http://localhost:5001/

check visualizer by http://localhost:8080/

Fifth, update the compose, and redeploy .

$ docker stack deploy --compose-file docker-stack.yml vote
Updating service vote_db (id: xtj2cfti451f0m2o8c512l47b)
Updating service vote_vote (id: ur903zugvgqqfqtbk7icf66me)
Updating service vote_result (id: wkvh4w7ajcj1chup9ip6fmf97)
Updating service vote_worker (id: nmwilsr6r8f0re9005faaz5yu)
Updating service vote_visualizer (id: zl6q0johuc1bar77cumywfl3p)
Updating service vote_redis (id: 9p1nzisw7d7ostpf79e76qiu9)

then 
do vote by http://localhost:5000/
check vote result by http://localhost:5001/

 Sixth, Remove the stack

$ docker stack rm vote
Removing service vote_db
Removing service vote_redis
Removing service vote_result
Removing service vote_visualizer
Removing service vote_vote
Removing service vote_worker
Removing network vote_frontend
Removing network vote_backend
Removing network vote_default