Alex Chiritescu

Alex Chirițescu

My #purpose is to help create #safe work #environments that enable #people to be #happy, #creative, #effective and #proud of their work.

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3 minutes read

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?

What?

Why?

What? continued

  • 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)

THE END

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