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Kubernetes Steps of an API Request

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Recommended Reads: Admission Controllers

Steps of an API Request

  • Details on what happens when we submit a request to the k8s API:
    • attachments/Pasted image 20230510130038.jpg
    • When we do a k apply command then the yaml file is converted to JSON by kubectl and then sent to the API server.
    • The first component of the API server is the API HTTP Handler.
      • It is an HTTP server listening for requests.
    • The second component of the API server is Authentication.
      • It checks if the user or the service account should be allowed to access the cluster.
    • The third component of the API server is Authorization (RBAC).
      • This checks if the user or the service account can list, delete, create resources in the cluster.
      • This is where RBAC rules are evaluated.
    • The fourth component of the API server is Mutation Admission Controller.
      • It looks at our YAML and modifies/mutates it.
      • For example if we forget to add the default storage class to our yaml then the mutation admission controller will add it.
    • The fifth component of the API server is Schema Validation.
      • It validates if the resource we have sent has a valid schema. Basically checking if the yaml is valid or not.
    • The sixth component of the API server is Validation Admission Controller.
      • It comes in when we try to deploy a pod in a namespace that DOES NOT exist.
  • To read more on validating or mutating admission controller read this.
If we manage to pass the Validation Admission Controller then our yaml file is saved in etcd.
  • Examples of custom admission controllers:
    • attachments/Pasted image 20230510130301.jpg

References

Last updated: 2023-05-11