Docker Swarm Contd

• Each Docker Host can be manager or worker
• In Docker Swarm we specify the desired state
• Terminology
• Nodes:
  • The instance where docker is installed.
  • Two Types
  • Manager Node:
    • We communicate with Manager to specify our service definitions
    • This node will assign unit of work called as tasks to the Worker nodes
  • Worker Node:
    • They recieve & execute the tasks dispatched from manager node
    • An agent runs on the worker node and reports on the tasks assigned to it
• Swarm Setup:
• 3 ubuntu instances and install docker (ensure each instance is atleast 2 vcpus 4 GB of RAM)
  
• Install Docker on all the three nodes
• On the designated manager node execute

docker swarm init --advertise-addr 172.31.46.65

* Now login into worker nodes and execute docker swarm join command
docker swarm join --token SWMTKN-1-3cwg22o4p780ip3enz9g5ijzqogl1v5s1a89egwcp56j5pkyk1-5baqd98h34xiabjrtmp0oiqxz 172.31.46.65:2377
* Verify The nodes docker node ls in the manager

* verify the networks in the manager and nodes docker network ls

* now lets create service

docker service create --replicas 3 --name apache httpd

* To delete the service execute docker service rm apache

• Now Lets create a docker service and verify the network connectity
  
• Exercise: Specify how to verify communication between containers on different nodes in swarm