Resource:

• This is an open source container orchestration framework (coordination and management of multiple containers)

• Helps manage containers → Kubernettes helps manage applications which are made up of Containers, and helps you manage them in different environments (Cloud, Physical machines, VMs, or even Hybrid envs)

• What problems does K8s solve?

  • From Monolith to Microservers

  • Increased usage of containers

    

  • Rise of containers → we need a container management tool to manage them across multiple environments

• Features of K8s

  • High availability, and scale up and down as needed
  • Disaster recovery → Backup and restore

• Kubernetes Architecture

  • 1 master node (Virtual or Physical Machine) which is connected by worker nodes
  • Each worker node has a Kubelet node on it (Kubernettes process which allows the clusters to communicate w/ each other, and execute tasks, etc)
  • Each worker node has containers deployed on it (of different applications)
  • Worker node is where the applications are running (containerized microservices)
  • Worker nodes have higher workload, and much bigger and more resources (as they run the apps)
  • Master node → Runs several k8s processes: API, Controller Manager, and Scheduler
  • Master Node → Control Plane Nodes (Handful of master process, but much more important as it has control to everything!)
  • Usually we run multiple copies of master nodes incase we lose 1 or 2, we can still manager our containers with the replacement
    • API server, entry point to the kubernettes cluster → This is the process which different clients can talk to i.e. UI, APIs, CLI
    • Controller Manager → Keeps track of whats happening in the cluster (if something needs to be repaired, if a container died and needs to be restarted.. etc)
    • Scheduler → Ensures Pods placements (Responsible for scheduling containers on different nodes based on capacity, and load)
    • ETCD → Kubernettes backing store (Contains the Current State of the K8s at any time → has configuration data of and state of every worker node
      • Also used for backup and restore by snapshotting all states from this etcd
    • Virtual Network → Allows the communication between master and worker nodes → Creates one unified machine

• Kubernetes Components — There is alot!

  

  • We will look at each component w/ the help of building a simple webapp, with a database
  • Worker Node / Node → VM or physical server
  • Application Pod → Smallest unit in Kubernetes, which offers abstraction over container. This creates a running env on top of the container → This allows us to switch away to any container (don’t have to be tied to just Docker, … etc)
    • Usually 1 app / pod
    • pod can be a Database on the same worker node
    • Each pod gets it’s own IP address, which allows us to communicate w/ each other using that IP address
    • New IP address on creation
  • Pod → Layer on top of the container → Abstraction over container → Allows us to replace containers,