Docker networking contd..

• Lets look at the following scenario
  
• As number of Docker Hosts increase the complexity of running containers becomes difficult to manage.
• A container in one host (srv1) trying to connect to container in other host (srv3) is not possible with bridge network
• Failure scenarios:
  • What happens if the srv1 is down
  • What happens when a container in srv1 is down
• Performing the above actions are tedious.
• Lets just think of networking perspective, docker has a mode called as swarm which enables multi-host docker networking and also it gives orchestration features.

Docker Swarm

• Overview
  
• Refer Here for the blog
• Refer Here for the networking and interfaces
• All the nodes should be reachable to each other
• docker should be installed on all the nodes
• Create two linux servers and install docker in it
• Select any linux server (node-1 – powershell in images) and initialize swarm

qtdevops@dockernode-1:~$ docker swarm init --advertise-addr "10.2.0.6"
Swarm initialized: current node (qo5x9l0pngi8k20zeisrv5lc9) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join --token SWMTKN-1-3prx9d5k19977wurpimwl1v0ufon8e22u6uns3s3d38aa4c3rx-9stw2ke6ytpwutuggn1zb0kn3 10.2.0.6:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

• On the manager two extra docker networks will be created
  
• Pictorial reprsentation
  
• Now execute docker swarm join command on the node-2
  
• Lets look at networks
  
• Communication from one to other container will look as shown below
  
• Lets see the list of nodes in docker swarm manager
  
• Lets create a service of nginx

docker service create --replicas 2 --name nginx-srv nginx