Kubernetes Steps of an API Request in API Server

Links: 111 KodeCloud Index
Recommended Reads: Admission Controllers

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Steps of an API Request

• Details on what happens when we submit a request to the k8s API:
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  • 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:
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References

• Kubernetes API Explained - YouTube

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Last updated: 2023-05-11