WRITELOOP

KUBERNETES COMPONENTS

2020 January 22

(reference: https://www.youtube.com/watch?v=Krpb44XR0bk&feature=youtu.be)

Concepts

Master: the node responsible for the workload orchestration Minion: the node that will run a workload A node can have both roles.

Components:

Node

A machine (physical or virtual) will be a master/minion.

Pod

A single unit of work. It can have one or more containers.

Service

Runs inside a node. Exposes ports internally and/or externally. It is also a load balancer.

Ingress

Receives requests and forwards them to services.

ConfigMap

“Environment variables” that you attach to a pod.

Secret

Sensitive “environment variables”, like passwords, api keys, certificates.

Volumes

“External hard drives” to the cluster. k8s does not manage volumes, just attaches itself to them.

Deployment

In practice, is what you work with. With a deployment you specify app replicas, scale apps up and down, etc…. Apps like DBs cannot be replicated using deployments, since they are more sensitive to simultaneous writes.

Statefulset

Replication/deployments for apps like DBs. It makes sure reads and writes are synchonized.