K8s Architecture

Question 1

what are the 3 processes to manage a pod?

Answer 1

container run time (like docker eg) (needs to be installed on every node)
kubelet (scheduler) communicates with container run time and the node (it takes configuration and runs a pod with container inside) (assigns resources like cpu, ram storage etc to the node)
kubeproxy allows you to forward requests from services to pods (this must be installed on every node) (this is also intelligent because it will forward requests from application to the database inside the same node to not gain more overhead)

Question 2

What do master nodes do?

Answer 2

They decide whether to schedule a pod

They decide whether to restart a pod if a replica pod dies.

Question 3

What 4 processes run on master node to control cluster state and worker nodes?

Answer 3

API server (used when you want to deploy application into a cluster interact with api server using a client like a ui or Kubernetes dashboard).

This is like a cluster gateway which gets updates or queries from cluster. also acts as gatekeeper for authentication.

Scheduler (schedule a request for a new pod, Api server will authenticate your request then hand it over to scheduler to start application on one of worker nodes). Kubelet will then execute the request.

Controller manager detects state changes (crashing of pods for example). This makes a request to the scheduler to recycle dead pods, calculates which nodes should have new pods. Then makes a request to kubelet to actually re-start those pods.

etcd is key value store of cluster state. Every change is updated in the key value store (when a pod dies or when pod gets scheduled)

Question 4

What is minikube?

Answer 4

1 node cluster
master and worker processes run on one node
docker pre installed
runs using a hypervisor such as virtual box.

Question 5

What is Kubectl?

Answer 5

way to create components on the node.

basically a cli

Question 6

What is the layers of abstraction

Answer 6

deployment
replicaset
pod
container