DevOps Classroom Series – 10/Nov/2020

Docker Multihost Networking and Swarm

• Create 3 servers connected to each other with in a network and install docker on all the three servers

• How can we enable communication b/w two container running on different hosts

• Docker has network driver which is called as overlay which can help in connecting two containers running on different hosts

• Refer Here to understand overlay networks

• When we are working with multiple docker hosts. It becomes extreemly important for us to ensure

  • avoid failures
  • Scale the containers
  • Simplicity
  • Zero Downtime deployments

• What we are looking for some software which manages this cluster and Orchestrate. This is exactly where Docker Swarm, Kubernetes and Apache mesos (many more) come into play.

• Docker Swarm creates an overlay network b/w multiple nodes. Refer Here

• Docker Swarm is a cluster and it has two types of nodes

  • Manager Node:
    • This is point of contact for us to execute the desired state (Service).
    • This nodes dispatches a unit of work (task) to the worker nodes
    • You can have multiple manager nodes (only one will be primary manager)
  • Worker Node:
    • They recieve and execute the tasks dispatched from manager nodes
    • Mulitple Nodes can be created
    • Agent that runs on this node reports the status of tasks assigned to it back to manager

• Docker Swarm Representation

• Create the docker swarm cluster as mentioned in the above link

• Generally docker services will be exposed to the outside world using load balancers.

• Experiment by doing

  • docker network ls (on manager and worker nodes)

• Some reference applications for conterization

  • openmrs
  • shopizer
  • nopcommerce (linux)