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Semicolony ELI5 · comic

Kubernetes.

An air-traffic controller for your containers: you say what you want running, it keeps it that way.

  1. Three, please.
    desired: replicas: 3
    1

    You declare what you want: “keep three copies of this app running.”

  2. control
    2

    The controller schedules those copies (pods) onto whichever machines have room.

  3. want 3 have 3
    3

    It constantly compares what you asked for against what’s actually running.

  4. One down — replacing.
    crashed → replaced
    4

    A pod crashes? It notices the gap and starts a replacement automatically.

  5. 3 10 it fills in the rest
    5

    Need more? Change the number to ten and it fills in the rest.

  6. swap gradually — no downtime
    6

    Deploying a new version? It swaps pods gradually, so there’s no downtime.

Declare the state you want; the controller keeps reality matching it.
Semicolony semicolony.dev/eli5/kubernetes/comic
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