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Kubernetes
Kubernetes is an open-source container orchestration system originally developed by Google in 2014. It provides a platform to manage the lifecycle and networking of containerized applications across clusters of hosts. Kubernetes handles tasks like replication, rollouts, and health checking and allows developers to deploy containerized applications without worrying about infrastructure management. It uses concepts like pods, nodes, controllers and services to abstract away the details of deploying and maintaining applications in production.
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Kubernetes
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- 2. “The views, thoughts,opinions are solely to myself and does not represent my current and previous employers.”
- 5. Kubernetes • From Google,2014. Currently Open Source. • Container Orchestration Engine • Replaces AWS EC2, Azure compute, … • Monolithic, one-size fits all collection of functions • Core of Google Cloud Platform
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- 7. - 90’s • BuyHardware • Install O/S, dependencies • Operate service & infra. • Idea • Application code
- 8. - 2010 • BuyLess Hardware • Operate service & infra. • Idea • Application code • Install O/S, dependencies
- 9. - 2016 • Operateinfra. • Idea • Application code • Install O/S, dependencies • Operate service
- 10. - Current • Operateinfra. • Idea • Application code, faster • Install O/S, dependencies, faster • Operate service, faster
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- 12. Docker • Uses resourceisolation features of Linux kernel • cgroup for isolating usage of CPUs, disk I/O • namespaces for isolating process IDs, hostname, file system • Lightweight image without O/S - “Build once, run everywhere” • Minutes to boot VM vs. Second to start container
- 13. Docker’s so good… AndI need to run 1000s dockers?
- 15. Kubernetes • Manages life-cycleof containers (≈ EC2) • Controllers for replication and coordination of containers (≈ Autoscaling, CloudFormation) • Manages networking and storage (≈ EC2, Elastic IP) • Convenient object management (≈ IAM, Tagging) • Built-in Cloud integration
- 16. Pod • The basicbuilding block: 90% of dev time spent here • Encapsulates application container • A pod runs a single container: most use-cases • A pod runs multiple containers
- 17. Pod kubectl get pods kubectldescribe pod myapp-pod kubectl delete pod myapp-pod kubectl logs myapp-pod kubectl exec myapp-pod -it /bin/sh
- 18. Node • Host machinerunning Pods (containers) • VM or physical machine • VM Instances in EC2, GCP, … • Runs kubelet, kube-proxy, and docker • CPU and memory capacity for scheduling • SRE’s concern (add, retire, upgrade)
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- 20. Controllers • Pod =unit of single or co-located containers • Controllers = Coordination over set of pods • E.g., front-end pods, database pods, … • Unit of deployments (where as Pod is unit of debugging)
- 21. Replication Controller kubectl create-f ./replication.yaml replication controller “nginx” created
- 22. More Controllers • Deployments:changes actual state of pods to desired state • StatefulSets: guarantees about the ordering and uniqueness of pods • DaemonSet: ensures all Nodes run a copy of a pod • Jobs: run batch type pods • The list grows…
- 23. Services • Not reallyabout services … • Pods are ephemeral • External endpoint: public IP, stable port, and DNS • Equivalent to Elastic IP or load balancer in EC2 • Iptable as implementation mechanism
- 24. Typical design sofar Next things are clever
- 25. Objects • Persistent entities:Pod, Node, Controllers, Services, … • Declarative spec describes desired state • K8 ensures actual state = desired state • Declarative programming vs. service oriented architecture
- 27. Getting a jobdone S3 EC2 IAM ELB May I get the image ID? Can you run this image? Can I get the password? Can you run it behind LB?
- 28. Wow such cloud Iam so empowered!
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- 30. Labels and Selectors •Objects can be labeled (key-value pair) • Match one object kinds to another • Schedule pods to nodes • Map service/controllers to set of pods
- 32. Such Cloud way What’sthe image ID? Wth, dependency updated! Crap, instances crashed What’s the current ID? Ok change it now
- 33. Label Things changed, but I’llfigure them out
- 34. Secrets • Object thatcontains a sensitive data • Passwords, OAuth token, etc • Production service needs secure token passed to Pods
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- 37. Kubernetes • Maybe Googleinvented a weapon against AWS • Monolithic architecture with collection of useful tools • Declarative style makes it easier to program • Go for it. It works really well.