Kubernetes Workflow for Absolute Beginners

Hello Everyone, let’s discuss the kubernetes workflow. Whenever we are executing any command let’s say “kubectl create pod nginx”, how the pod request work in the backend and how a pod is got created:

1. The request is authenticated first and validated.
2. The “kube-api-server” creates a POD object, without assigning it to a node, updates the information of the newly created pod in “ETCD Cluster” and updated/shows us a message that a POD is got created.
3. The “kube-scheduler” which is continually monitoring the “kube-api-server” gets to know that a new pod is got created with no node assigned to it.
4. The “kube-scheduler” identifies the right node (according to pod resource requirement, pod/node affinity rules, labels & selectors etc.) to place the new POD and communicate back to the “kube-api-server” (with the information of the right node for the pod)
5. The “kube-api-server” again updates the information to the “ETCD Cluster” received from “kube-scheduler”.
6. The “kube-api-server” then passed the same information to the “kubelet” on the appropriate worker node identified by “kube-scheduler” in the 4th step.
7. The “kubelet” then creates the pod on node and instructs the “Container Runtime Engine” to deploy the application image/container.
8. Once done, the “kubelet” updates the information/status of the pod back to the “kube-api-server”.
9. And “kube-api-server” updates the information/data back in the “ETCD Cluster”.

Kubernetes workflow

And that’s how a pod is got created.

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Refer Other useful Kubernetes Articles:

Node Affinity In Kubernetes

Kubernetes Services for Absolute Beginners — NodePort

Kubernetes Services for Absolute Beginners — ClusterIP

Kubernetes Services for Absolute Beginners — LoadBalancer

labels-and-selectors-in-kubernetes

Kubernetes workflow for Absolute Beginners

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