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Kubernetes Introduction
- 1. One of the most unpolished Kubernetes introduction presentations ever given on a Thursday afternoon from Freiburg, Germany, ever Martin Danielsson -- 2017-01-05 Haufe-Lexware GmbH & Co. KG, CTO Office Twitter: @donmartin76, GitHub: DonMartin76
- 2. You might have figured, this is the Kubernetes logo
- 3. Thank you for your attention! Just kidding.
- 4. What is Kubernetes? “Kubernetes is an open-source platform for automating deployment, scaling, and operations of application containers across clusters of hosts, providing container-centric infrastructure.” http://kubernetes.io/docs/whatisk8s/ Holy smokes!Which means?
- 5. What does Kubernetes do? • Provide a runtime environment for Docker containers • Scale and load balance docker containers • Abstract away the infrastructure containers run on • Monitor/health check containers • Declarative definition for running containers • Update containers (also rolling updates) • Storage mounting (allow abstracting infrastructure) • Service discovery and exposure • Labelling and selection of any kind of object (we‘ll get to this)
- 6. What does Kubernetes fucking not do? • Provide any additional services than just Docker • Compile or build your source code (needs images) • Provide real orchestration, relies on containers working independently • Mandate or provide any kind of special configuration language • You’re free to do whatever you want • But: You have to find out a way yourself
- 8. Recap - Docker? Docker Host (e.g. Ubuntu 16.04 LTS) Container nginx Container node.js App Container PostgreSQL • Docker containers share Kernel with Host • Many containers can efficiently run on one Host • Powerful developer tooling • Dockerfiles are used to build images • A Docker Registry can store Docker images • Haufe’s registry.haufe.io • Official hub.docker.com • Docker Engine used by Kubernetes under the hood • Kubernetes is alternative to Docker Swarm • Older, more mature • Used e.g. by GCE (Google Container Engine)
- 9. Kubernetes and Docker • Kubernetes adds functionality to Docker • Manages a set of Docker Hosts, forming a Cluster • Takes care of Container scheduling • Supervises Docker containers • Kubernetes is replacement/alternative for Docker Swarm
- 10. Node workload workload workload Node workload workload workload Kubernetes Master(s) apiserver controllers Node workload workload workload All blue boxes are Docker Hosts (VMs) Kubernetes Components are also running as stateless containers! etcd (cluster) scheduler Deployment Architecture
- 11. Node 1 Kubernetes Runtime Pod X Container A Container B Pod Y Container C Node 2 Pod Y Container C Pod Z Container D Node 3 Pod Z Container D Pod X Container A Container B
- 12. Deployment Replica Set Pod Spec Abstractions (1) - “Boxes in boxes” Container Spec Container Spec Docker image Environment variables Storage Claims Node selector Service labels How many Pods should run? How are updates handled? Rolling/recreation
- 13. Abstractions (2) - Services Pod Pod Pod Pod PodService B, select “B”, http://ser vice-b A A A B B Service A, select “A” e.g., http://ser vice-a
- 14. Abstractions (3) - Other things • Jobs (one-off containers) • DaemonSets (one container per node) • StatefulSet (handles lifetime of pods differently)
- 15. Exposing Services (1) - NodePort Node 1 Node 2 Node 3 Service A 31234 (non-privileged) 31234 31234 Can be used to put an external Load Balancer in front of a service
- 16. Exposing Services (2) - LoadBalancer Node 1 Node 2 Node 3 Service A • Depends on Cloud Provider (Azure, AWS,…) how this is done • Will provision a Load Balancer on the cloud provider’s infrastructure • (e.g. Elastic LB, Azure LB,…) LB
- 17. Exposing Services (3) - Ingress Kubernetes Cluster Service A Service B Service C Pod Pod Pod Pod Pod Pod Pod Pod Pod … LB Ingress Definition Ingress Controller (SNI, TLS) • E.g., “route Host x.y.z to Service A”, “Use TLS Certificate abc for host x.y.z” • Abstract definition of rules • Implemented by Ingress Controller • Flexible; leverages “LoadBalancer” on cloud provider • Can provide SNI (Server Name Indication) and TLS termination
- 18. Working with kubectl $ kubectl apply -f deployment.yml Created deployment “nginx” $ Kubernetes Master(s) apiserver scheduler ~/.kube/config Authentication/ Authorization • kubectl is a convenient way to talk to the Kubernetes API • Uses ~/.kube/config for AuthN/Z
- 19. Example kubectl YAML file apiVersion: extensions/v1beta1 kind: Deployment metadata: name: idesk-mobile-2851 spec: replicas: 2 # keep the latest three deployments on k8s revisionHistoryLimit: 3 template: metadata: labels: service: idesk-mobile-2851 feature: "false” spec: containers: - env: - name: API_GATEWAY_HOST value: https://api.idesk-apim.haufe-ep.de - name: CLIENT_ID value: "ad283bd8273bdbe9a72bdef” image: "aurora/aurora.mobile.client:v2851” name: idesk-mobile ports: - containerPort: 80 protocol: TCP restartPolicy: Always imagePullSecrets: - name: aurora-registry-haufe-io $ kubectl apply -f idesk-mobile.yml Created deployment “idesk-mobile-2851” $ kubectl get po NAME READY STATUS RESTARTS AGE idesk-mobile 1/2 Running 0 10s $ Container(s) Pod Replica Set Deployment
- 20. Example Service YML apiVersion: v1 kind: Service metadata: labels: service: idesk-mobile-2851 feature: ”true” name: idesk-mobile-2851 spec: type: NodePort ports: - name: “https” port: 443 protocol: TCP targetPort: 443 nodePort: 31851 selector: service: idesk-mobile-2851 status: loadBalancer: {} Reachable over any Agent IP: https://aurora-k8s.haufe-ep.de:31851
- 21. Demo • Add an nginx Deployment • Add a service • Expose service via an Ingress definition • Kubernetes Dashboard • Deleting with a selector filter
- 22. Example Ingress YML apiVersion: extensions/v1beta1 kind: Ingress metadata: name: nginx-demo spec: rules: - host: nginx-demo.donmartin76.com http: paths: - path: backend: serviceName: nginx-demo servicePort: 80