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Kubernetes

CIS 1912

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HW1 Recap

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Docker/Docker Compose

Recap

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Docker

Recap

docker run

Container

Task app

Running on port 80

Local Machine

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Docker

Recap

docker run -p 80:80

Container

Task app

Running on port 80

Local Machine

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Docker

Recap

docker run -p 80:8000

Container

Task app

Running on port 80

Local Machine

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Docker

Recap

docker run -p 8000:80

Container

Task app

Running on port 80

Local Machine

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Docker Compose

Recap

services:

web:

Image: web:v1

command: poetry run uvicorn main:app --host 0.0.0.0

--port _____

ports:

- "_____:_____"

depends_on:

- redis

​

redis:

image: redis:latest

command: ["redis-server", "--appendonly", "yes"]

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Docker Compose → k8s

Clustering Wishlist

  • Declarative
  • API-Driven
  • Open-source
  • Community
  • Technically solid
    • Horizontal scaling
    • High Availability
    • Networking
    • Observability

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What is Kubernetes?

  • Tool for orchestrating containers (Docker in our case)
  • Takes us from local development to production

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Pods

  • Base unit of work
  • Each has an IP address
  • Almost always 1 to 1 with container (like Pod 1)
  • Can be labeled for later querying
  • What happens if pod errors or fails?

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Pods

apiVersion: v1

kind: Pod

metadata:

name: static-web

labels:

app: nginx

release: stable

spec:

containers:

- name: web

image: nginx:1.21.6

ports:

- name: web

containerPort: 80

protocol: TCP

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Nodes

  • Hosts for pods
  • VMs, your laptop, physical servers
  • Main/Master & Worker nodes

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Deployments

  • Group of Pods
  • Grouped by label

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Deployments

apiVersion: apps/v1

kind: Deployment

metadata:

name: nginx-deployment

spec:

selector:

matchLabels:

app: nginx

replicas: 2 # pod count

template:

metadata:

labels:

app: nginx

spec:

containers:

- name: nginx

image: nginx:1.14.2

ports:

- containerPort: 80

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Deployments

apiVersion: apps/v1

kind: Deployment

metadata:

name: nginx-deployment

spec:

selector:

matchLabels:

app: nginx

replicas: 2 # pod count

template:

metadata:

labels:

app: nginx

spec:

containers:

- name: nginx

image: nginx:1.14.2

ports:

- containerPort: 80

If we define a deployment,

do we need to define pods?

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Services

  • Network pods together
  • Grouped by label

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Services

apiVersion: v1

kind: Service

metadata:

name: my-service

spec:

selector:

app: nginx

ports:

- protocol: TCP

port: 80

targetPort: 9376

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https://dev.to/lovestaco/6-kubernetes-ports-a-definitive-look-expose-nodeport-targetport-more-2enc

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Kubernetes Demo (github.com/cis1912/kube-demo)

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Cattle not Pets

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​

k8s in practice

…unless you h8 k8s

✨Extra Info✨

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Microservice

apiVersion: v1

kind: Service

metadata:

name: micro-service

spec:

selector:

app: MyApp

ports:

- protocol: TCP

port: 80

targetPort: 9376

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Microservice

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Microservice

  • One task at a time
  • Stateless
  • Scales separately from other services
  • Communication is key

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Microservice

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Fin

  • HW1 due next week!
  • Come to office hours!

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Fin

  • Lab 2: Local Kubernetes will be out tonight!
  • Come to office hours!

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Credits

Thanks to the kubernetes team for awesome images!!

Kube images:

https://kubernetes.io/docs/tutorials/kubernetes-basics/

Networking images:

https://matthewpalmer.net/kubernetes-app-developer/articles/kubernetes-ingress-guide-nginx-example.html

​