Alex Chiri's Blog

What and Why is (there) Kubernetes?

Not long ago, I posted a small article called "Why is (there) Kubernetes?". Its content inspired me to create a short presentation trying to answer the questions "What and Why is there Kubernetes?". See below the recording and its summary after.

What and Why is there Kubernetes?

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What? continued

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  • Let's have a look at this again
  • I see Kubernetes being composed of logical 2 components
    • Master and Workers
    • An imperfect analogy
      • Master <-> our brain
      • Workers <-> the other parts of our body that our brain controls
    • The Master includes (besides other components)
      • The API server - most of the communication with the cluster and between its components happens through the API
      • etcd - a key value database where the state of the cluster is kept (the cluster "memory")
    • Zooming on a Worker (which is basically a VM) - a cluster can have several workers
      • There are several Kubernetes processes
      • And a number of pods which each contain 1 or more Docker containers
      • The services deployed on the cluster run in these containers
  • When we deploy a service, we tell Kubernetes what is the end state we want (how many instances of the service, how should it be exposed outside the cluster etc.)
  • And if it has the resources available, it will make it happen
    • Kubernetes will try to spread the instances (pods) along its worker nodes
    • Or if it doesn't have enough nodes with available resources, it might put all instances (pods) on the same node
  • One more thing... namespaces
    • Pods, services, many Kubernetes resources are organised in namespaces across nodes
    • Namespaces provide isolation between the resources in the cluster
    • You can assign roles to users and give them access to do specific actions on specific namespaces
    • In reality, pods might look more like this when it comes to namespace distribution across nodes
      • (rectangles are pods of different sizes, colours represent the namespace they are part of)


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