Lab: Docker SWARM Quick Dive

Create a 5 nodes (3 masters, 2nodes) swarm cluster using http://play-with-docker.com

Launch a Visualizer on Master (SWARM Manager)

docker run -itd -p 8080:8080 -v /var/run/docker.sock:/var/run/docker.sock schoolofdevops/visualizer

Deploying Service with swarm - The imperative way

docker service create --name vote schoolofdevops/vote

docker service ls
docker service inspect

docker service  update --publish-add 80:80 vote

Try accessing port 80 on any of the nodes in the swarm cluster to validate.

Scaling a service

docker service scale vote=4
docker service  ls
docker service scale vote=2

Cleaning Up

docker service rm vote

Orchestrating Applications with Stack Deploy

file: stack.yml

version: "3"

networks:
  nw01:
    driver: overlay

volumes:
  db-data:

services:
  vote:
    image: schoolofdevops/vote:v1
    ports:
      - 80
    networks:
      - nw01
    depends_on:
      - redis
    deploy:
      replicas: 8
      update_config:
        parallelism: 2
        delay: 20s
      restart_policy:
        condition: on-failure  

  redis:
    image: redis:alpine
    networks:
      - nw01

  worker:
    image: schoolofdevops/vote-worker
    networks:
      - nw01
    depends_on:
      - redis
      - db

  db:
    image: postgres:9.4
    networks:
      - nw01
    volumes:
      - db-data:/var/lib/postgresql/data

  result:
    image: schoolofdevops/vote-result
    ports:
      - 5001:80
    networks:
      - nw01
    depends_on:
      - db

You could also copy the above file using the followinng command,

wget -chttps://gist.githubusercontent.com/initcron/8a5ebd534df74ab2a83e96218b56137d/raw/9e748637aed121b67ceddeca8678750596c81ab7/stack.yml

Deploy a stack

docker stack deploy --compose-file stack.yml instavote

Validate

docker stack ls

docker stack services instavote

docker service ls

docker service scale instavote_vote=4

Deploying a new version

Update stack.yml with the new version of the image

....
services:
  vote:
    image: schoolofdevops/vote:v2
  .....

    deploy:
      replicas: 8
      update_config:
        parallelism: 2
        delay: 20s
      restart_policy:
        condition: on-failure  
...

Deploy using the same command as earlier,

docker stack deploy --compose-file stack.yml instavote

Fault Tolerance

• Delete a node
• Observe the node being removed from cluster
• Observe tasks getting rescheduled automatically on available nodes