DevOps Classroomnotes 25/Jun/2022

Docker Networking

• Docker Networking Architecture is based on Container Network Model (CNM)
• Refer Here for the docker container networking article

Cluster

• A server cluster is group of two or more nodes (servers), that run in parallel to acheive a common goal
• A cluster functions as if it were a single system. A user accessing the cluster should not need to know whether the system is a cluster or individual machine
• Benifits:
  • High Availability
  • Load Balancing
  • Scaling
  • Performance
• To manage clusters we generally use cluster orchestration software
• Container Orchestration Softwares
  • Docker Swarm
  • Kubernetes
  • Mesos
• Using Container Orchestration Softwares, we enable
  • multi node setups
  • we express the desired state rather than commands to create containers
• Generally Orchestration softwares have two kinds of nodes
  • master nodes (manager)
  • nodes (worker)
• To decide which node is manager there are consensus algorithms like RAFT etc which will choose the manager by election.

Docker Swarm Setup

• Refer Here for the article
• Create 3 ubuntu instances and install docker in them
• explore swarm command line
  
  
• Note the output

Swarm initialized: current node (4zbhonvbfzpzs2dzbbgjcmfz3) is now a manager.

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

    docker swarm join --token SWMTKN-1-02wrpqrep3ytgxynjurslwjseu4898o1vvbi0cozh00eth7ova-aswifi8z4zrdwmnl51nzyd7li 172.31.7.10:2377

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

• When the swarm is initialized docker will create an overlay network
  
• Docker has one more subcommand node
  
  
• Basic interaction diagram
  
• In swarm we create services
  
  
  
  
• Note: Sending the image to docker hub
  
• For experimentation lets use the container image shaikkhajaibrahim/qttestapp:1.0 Refer Here
• Create a service using test app docker service create --name testapp --replicas 2 --publish published=5001,target=5000 shaikkhajaibrahim/qttestapp:1.0
  
• To access the test app use any nodes ip with 5001
• Understanding how overlay works Refer Here