Docker Swarm

Docker Swarm Initialization

1.Install Docker and initial

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2. Initialize Docker Swarm Cluster

Select everyone to set up cluster.

docker swarm init --advertise-addr <cluster_ip>        

You can get a swarm token like this?ddocker swarm join --token SWMTKN-1-2142i8zn <cluster_ip>:2377

• If you want?mutiple managers, use?docker swarm join-token manager?to get manager token.?docker swarm join-token worker?to get worker token.
• We can also use?docker node promote <NODE_NAME>?to promote a node to manager.

3. Add Nodes

Use?docker swarm join --token SWMTKN-1-2142i8zn <cluster_ip>:2377?to add nodes.

4. Remove Nodes

Use?docker swarm leave?to remove nodes.

5. View Nodes and Services

Use?docker node ls?to view nodes. Use?docker service ls?to view services.

Docker Swarm Configuration Examples

1. Create a nginx service

docker service create --name test-nginx --publish 80:80 --replicas 3 nginx        

2. Check service status

docker service ls
docker service ps test-nginx # check nginx service        

3. Scale service

docker service scale test-nginx=5        

4. Remove service

docker service rm test-nginx        

Docker Swarm Compose

1. Docker Compose file

version: '3.8'

services:
  web:
    image: nginx:latest
    hostname: "{{.Service.Name}}-{{.Task.Slot}}"
    ports:
      - "80:80"
    deploy:
      replicas: 3
      restart_policy:
        condition: on-failure
      placement:
        constraints:
          - node.role == worker
    networks:
      - webnet

networks:
  webnet:        

placement.constraints means the node must be a worker node. It is optional.

2. Run Compose

docker stack deploy -c docker-compose.yaml test_nginx        

3. Change replicas number

Modify replicas number in docker-compose.yaml, and run Compose again.

docker stack deploy -c docker-compose.yaml test_nginx        

4. Remove Compose

docker stack rm test_nginx