Kubernetes Presentation

A presentation of the basics concepts of Kubernetes

Plan of the session

  • Introduction
  • Theorical part
  • Practice time !

Kubernetes Ecosysteme

Kubernetes kesako ?

Informations

  • What is a cluster versus a node ?
  • What is a namespace ?
  • Kubernetes in enterprise

And why ?

  • Use kubernetes as a PaaS
  • Deployment reproductibility
  • Resources quota flexibility
  • HA and network managed easily

Kubernetes on a project

  • Several clusters

Kubernetes on a project

  • Several clusters
    • dcluster: dev cluster
    • rcluster: prod cluster

Kubernetes on a project

  • Several namespaces
    • dteam1 : dev namespace of team 1
    • iteam1 : indus namespace of team 1
    • rteam1 : prod namespace of team 1

Kubernetes on a project

  • Several namespaces
    • dteam1
    • dteam2
    • dteam3
    • iteam1
    • iteam2
    • iteam3
    • rteam1
    • rteam2
    • rteam3
    • ...

View environment

Change context to switch between namespaces

cf: cheatsheet (kcontext, kns)

CLI and configuration

  • kubectl
  • ~./kube/config
  • More on that on the practice time

Some tools

  • kubectl aliases (cf cheatsheet)
  • k9s

K9S

Basic k8s resources

  • Pods

Basic k8s resources

  • Pods

						apiVersion: v1
						kind: Pod
						metadata:
							name: nginx-web
						labels:
							app: nginx
						spec:
							containers:
								- name: web
								image: nginx
								ports:
									- name: web
									containerPort: 80
									protocol: TCP

Basic k8s resources

  • Pods

Basic k8s resources

  • Pods
  • Deployment

Basic k8s resources

  • Deployment

						apiVersion: apps/v1
						kind: Deployment
						metadata:
						name: nginx-deployment
						labels:
						app: nginx
						spec:
						replicas: 3
						selector:
						matchLabels:
						app: nginx
						template:
						metadata:
						labels:
						app: nginx
						spec:
						containers:
						- name: web
						image: nginx:1.14.2
						ports:
						- containerPort: 80

Basic k8s resources

  • Deployment

Basic k8s resources

  • Pods
  • Deployment
  • Service

Basic k8s resources

  • Service

						apiVersion: v1
						kind: Service
						metadata:
							name: nginx-service
						spec:
							selector:
								app: nginx
						ports:
							- protocol: TCP
							port: 80
							targetPort: 8100

Basic k8s resources

  • Service

Basic k8s resources

  • Pods
  • Deployment
  • Service
  • Ingress

Basic k8s resources

  • Ingress

						apiVersion: networking.k8s.io/v1
						kind: Ingress
						metadata:
							name: minimal-ingress
						annotations:
							nginx.ingress.kubernetes.io/rewrite-target: /
						spec:
							rules:
							- http:
								paths:
								- path: /app
									pathType: Prefix
									backend:
										service:
											name: nginx-service
											port:
											number: 80

Basic k8s resources

  • Ingress

Basic k8s configuration resources

  • Configmap

Basic k8s configuration resources

  • Configmap
    • Can be used as environment variables
    • Can be used as files

Basic k8s configuration resources

  • Configmap

						apiVersion: v1
						kind: ConfigMap
						metadata:
							name: game-demo
						data:
						# property-like keys; each key maps to a simple value
							ENVIRONMENT_NAME: "INDUS"
							PROFILE: "indus-profile"
						# file-like keys
							application.properties: |
								bootstrap.servers= "http://kafka-server-indus:9092"
								max.poll.records=100    
							common.properties: |
								log_level="info"
								key.serializer="io.confluent.kafka.serializers.KafkaAvroSerializer"
								value.serializer="io.confluent.kafka.serializers.KafkaAvroSerializer"

Basic k8s configuration resources

  • Configmap
  • Secret

Basic k8s configuration resources

  • Configmap
  • Secret
    • Can be used same as Configmap use
    • Are base64 encoded

Basic k8s configuration resources

  • Secret

						apiVersion: v1
						kind: Secret
						metadata:
							name: mysecret
						type: Opaque
						data:
							USERNAME: YWRtaW4=
							PASSWORD: MWYyZDFlMmU2N2Rm

Basic k8s configuration resources

  • Configmap
  • Secret
  • Pod disruption budget

Basic k8s configuration resources

  • Configmap
  • Secret
  • Pod disruption budget
    • Limit non ready replicates of your app
    • Almost mandatory for production pods

Basic k8s configuration resources

  • Pod disruption budget

						apiVersion: policy/v1
						kind: PodDisruptionBudget
						metadata:
							name: nginx-pdb
						spec:
							minAvailable: 2 # maxUnavailable # % or fixed value
							selector:
								matchLabels:
									app: nginx

Deploy your app

  • Manually with kubectl apply 💪
  • Automatically triggered with Gitlab-CI 👍
  • The old way with Jenkins jobs 👎
  • Other solutions are possible

Deploy your app

  • How an example CI works ?
    • From develop : CreateBranch 🌳

Deploy your app

  • How an example CI works ?
    • From develop : CreateBranch 🌳
    • From the release branch : ReleaseTag 🔒

Deploy your app

  • How an example CI works ?
    • From develop : CreateBranch 🌳
    • From the release branch : ReleaseTag 🔒
    • From the newly created tag : Deploy 🚀

Deploy your app

  • How an example CI works ?
    • From develop : CreateBranch 🌳
    • From the release branch : ReleaseTag 🔒
    • From the newly created tag : Deploy 🚀
    • From the release branch : Merge to master ✅

Deploy your app

  • Focus on Tag and deploy steps

Deploy your app

  • Focus on Tag and deploy steps
  • Tag :
    • It can use a generic CI to build and deploy docker image.

Deploy your app

  • Focus on Tag and deploy steps
  • Tag :
    • It can use a generic CI to build and deploy docker image.
    • Maven is mainly used for that.

Deploy your app

  • Focus on Tag and deploy steps
  • Tag :
  • Deploy :
    • Use embedded files from the current repo or centralized files from git

Deploy your app

  • Focus on Tag and deploy steps
  • Tag :
  • Deploy :
    • Use embedded files from the current repo or centralized files from git
    • Files can be templatized using a templating tool

Deploy your app

  • Focus on Tag and deploy steps
  • Tag :
  • Deploy :
    • Use the embedded files from the current repo or the centralized files
    • Files can be templatized using a templating tool
    • Kustomize can be used to reuse components

Deploy your app

  • Focus on Tag and deploy steps
  • Tag :
  • Deploy :
    • Use the embedded files from the current repo or the centralized files
    • Files are templatized using d4x cli
    • Kustomize can be used to reuse components
    • Finally, just a command `kubectl apply -k` is used to deploy your app

Practice Time ! 🍾 🎉

Configuration

  • kubectl config view

Configuration

  • kubectl config view

						➜ kubectl config view 
						kind: Config
						apiVersion: v1
						preferences: {}
						clusters:
						- cluster:
								certificate-authority-data: DATA+OMITTED
								server: http://apiserver-my-cluster.my-domain.com:8443
							name: dcluster
						contexts:
						- context:
								cluster: dcluster
								user: user_ident
								namespace: dteam1
							name: dteam1@dcluster
						current-context: dteam1@dcluster
						users:
						- name: user_ident
						  user:
								token: REDACTED

Configuration

  • kubectl config view
  • Edit it at ~/.kube/config

View resources

  • kubectl get < type >

View resources

  • kubectl get < type >

						➜ kubectl get pod 
						
						NAME                 READY  STATUS            RESTARTS  AGE
						nginx-32j54h2        1/1    Running           0         48m25s
						front-app-34s53d4    0/1    Init 0/1          0         5s
						backend-app-45r65g6  0/1    CrashloopBackoff  4         19m58s

View resources

  • kubectl get < type >
  • kubectl describe < type > < name >

View resources

  • kubectl describe < type > < name >

						➜ kubectl describe pod nginx-32j54h2
						
						Name:         nginx-32j54h2
						Namespace:    dteam1
						Priority:     0
						Node:         docker-desktop/192.168.65.4
						Start Time:   Fri, 25 Mar 2022 17:50:27 +0100
						Labels:       app=nginx
						Annotations:  
						Status:       Running
						IP:           10.1.0.15
						IPs:
							IP:  10.1.0.15
						Containers:
							nginx:
								Container ID:   docker://ec3d2dc0aafbd88c7fba3a0d9bd3f4d49030bb88c28a3c0a6649c0a80794aeaf
								Image:          nginx:latest
								Image ID:       docker-pullable://nginx@sha256:4ed64c2e0857ad21c38b98345ebb5edb01791a0a10b0e9e3d9ddde185cdbd31a
								Port:           
								Host Port:      
								State:          Running
									Started:      Mon, 28 Mar 2022 13:24:49 +0200
								Last State:     Terminated
									Reason:       Error
									Exit Code:    255
									Started:      Fri, 25 Mar 2022 17:50:29 +0100
									Finished:     Mon, 28 Mar 2022 13:24:38 +0200
								Ready:          True
								Restart Count:  1
								Environment:    
								Mounts:
									/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-m67dr (ro)
						Conditions:
							Type              Status
							Initialized       True
							Ready             True
							ContainersReady   True
							PodScheduled      True
						Volumes:
							kube-api-access-m67dr:
								Type:                    Projected (a volume that contains injected data from multiple sources)
								TokenExpirationSeconds:  3607
								ConfigMapName:           kube-root-ca.crt
								ConfigMapOptional:       
								DownwardAPI:             true
						QoS Class:                   BestEffort
						Node-Selectors:              
						Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
						                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
						Events:
							Type     Reason          Age   From     Message
							----     ------          ----  ----     -------
							Normal   SandboxChanged  29m   kubelet  Pod sandbox changed, it will be killed and re-created.
							Normal   Pulling         29m   kubelet  Pulling image "nginx:latest"
							Normal   Pulled          29m   kubelet  Successfully pulled image "nginx:latest" in 1.355729459s
							Normal   Created         29m   kubelet  Created container nginx
							Normal   Started         29m   kubelet  Started container nginx
							Normal   Killing         9s    kubelet  Container nginx definition changed, will be restarted
							Normal   Pulling         9s    kubelet  Pulling image "nginx:1.0.0"
							Warning  Failed          8s    kubelet  Failed to pull image "nginx:1.0.0": rpc error: code = Unknown desc = Error response from daemon: manifest for nginx:1.0.0 not found: manifest unknown: manifest unknown
							Warning  Failed          8s    kubelet  Error: ErrImagePull
							Warning  BackOff         7s    kubelet  Back-off restarting failed container

Start troubleshooting

  • Only pods can have logs
  • kubectl logs < name >

Start troubleshooting

  • kubectl logs < name >

						➜ kubectl logs nginx-32j54h2 
						
						2022/03/28 11:24:49 [notice] 1#1: using the "epoll" event method
						2022/03/28 11:24:49 [notice] 1#1: nginx/1.21.6
						2022/03/28 11:24:49 [notice] 1#1: built by gcc 10.2.1 20210110 (Debian 10.2.1-6)
						2022/03/28 11:24:49 [notice] 1#1: OS: Linux 5.10.104-linuxkit
						2022/03/28 11:24:49 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
						2022/03/28 11:24:49 [notice] 1#1: start worker processes
						2022/03/28 11:24:49 [notice] 1#1: start worker process 31
						...

Start troubleshooting

  • kubectl logs < name >

						➜ kubectl logs --help

						# Retrieve only logs since Xh 
						➜ kubectl logs < name > --since Xh

						# Specify a container to display his logs 
						➜ kubectl logs < name > -c < container_name >

						# Follow the new logs printed by the pod
						➜ kubectl logs < name > -f

Start troubleshooting

  • Only pods can have logs
  • kubectl logs < name >
  • Stern (on github)

Start troubleshooting

  • Stern (on github)

						➜ stern nginx
						+ nginx-0 › nginx
						+ nginx-1 › nginx
						nginx-0 nginx 2022/03/28 13:15:29 [notice] 1#1: using the "epoll" event method
						nginx-0 nginx 2022/03/28 13:15:29 [notice] 1#1: nginx/1.21.6
						nginx-0 nginx 2022/03/28 13:15:29 [notice] 1#1: start worker processes
						nginx-0 nginx 2022/03/28 13:15:29 [notice] 1#1: start worker process 31
						nginx-0 nginx 2022/03/28 13:15:29 [notice] 1#1: start worker process 32
						nginx-1 nginx 2022/03/28 13:15:05 [notice] 1#1: nginx/1.21.6
						nginx-1 nginx 2022/03/28 13:15:05 [notice] 1#1: start worker processes
						nginx-1 nginx 2022/03/28 13:15:05 [notice] 1#1: start worker process 32
						nginx-1 nginx 2022/03/28 13:15:05 [notice] 1#1: start worker process 33
						nginx-0 nginx 2022/03/28 13:15:29 [notice] 1#1: start worker process 33
						nginx-0 nginx 2022/03/28 13:15:29 [notice] 1#1: start worker process 34

Edit resources

  • kubectl delete < type > < name >
  • kubectl edit < type > < name >
  • kubectl scale < type > --replicas X < name >

Edit resources


						➜ kubectl delete pod nginx-32j54h2
						pod "nginx-32j54h2" deleted

						➜ kubectl edit deploy nginx
						... open with vim
						deployment/nginx edited
						
						➜ kubectl scale deploy --replicas 2 nginx
						deployment/nginx scaled

Troubleshooting

  • Retrieve deployment template on the doc

Troubleshooting

  • Retrieve deployment template on the doc
  • Change image reference to a fake one

Troubleshooting

  • Change image reference to a fake one

						kind: Deployment
						spec:
							template:
								spec:
									containers:
										- name: nginx
										image: nginx:1.0.0 # image not exists

Troubleshooting

  • Retrieve deployment template on the doc
  • Change image reference to a fake one
  • Add resources quota with huge values

Troubleshooting

  • Add resources quota with huge values

						kind: Deployment
						spec:
							template:
								spec:
									containers:
										- name: nginx
										resources:
											limits:
												cpu: 12 # huge amount of cpu ! => forbidden 
												memory: 30Gi
											requests:
												cpu: 500m
												memory: 175Mi

Troubleshooting

  • Add resources quota with huge values

  • kubectl describe deploy < name >
  • kubectl describe replicatset < name >

Troubleshooting

  • Try it by yourself !

Cheatsheet

Cheatsheet link

The end

Thanks for your time ! ⏱

Some questions ? 🙋‍♂️