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How Kubernetes scheduler works
- 1. How Kubernetes Scheduler works HimaniAgrawal @himani_93
- 2. Agenda ● Scheduling inKubernetes ● Scheduler use cases ● How it works? ● Demo ● New in scheduler
- 3. Credits: Julia Evans(@b0rk)
- 4. In Kubernetes, scheduling refersto making sure that Pods are matched to Nodes so that Kubelet can run them. Ref: https://kubernetes.io/docs/concepts/scheduling/kube-scheduler/
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- 6. What can beachieved through scheduler? ● Ensure pods gets required resources ● Prioritize workload ● Configure geographical distance ● Reserve nodes for specific pods
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- 8. What scheduler needs? 12 3 Need to know a pod is NOT assigned to a node Choose a best fit node on which the pod can run Assign the pod to the node
- 9. What scheduler needs? 12 3 Need to know a pod is NOT assigned to a node Choose a best fit node on which the pod can run Assign the pod to the node
- 10. Scheduler is basically aKubernetes Controller
- 11. Kubernetes Controller Current stateTakes necessary actions so that desired state is achieved Once desired state is achieved, it updates the state of resources This continuously runs in a loop Credits: LEGO
- 12. What scheduler needs? 12 3 Need to know a pod is NOT assigned to a node Choose a best fit node on which the pod can run Assign the pod to the node
- 13. What scheduler needs? 12 3 Need to know a pod is NOT assigned to a node Choose a best fit node on which the pod can run Fi2 Assign the pod to the node a Filtering
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- 15. Pod manifest apiVersion: "v1" kind:Pod metadata: name: sansa spec: nodeName: "" containers: image: busybox
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- 28. What scheduler needs? 12 3 Need to know a pod is NOT assigned to a node Choose a best fit node on which the pod can run Fi2 Assign the pod to the node a Filtering b Scoring
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- 30. What scheduler needs? 12 3 Need to know a pod is NOT assigned to a node Choose a best fit node on which the pod can run Assign the pod to the node
- 31. Binding apiVersion: "v1" kind: Pod metadata: name:sansa spec: nodeName: "8" containers: image: busybox
- 32. API Server SchedulerKubelet create pod watch (create pod) create binding watch (create bind) Container Engine create container apiVersion: "v1" kind: Pod metadata: name: sansa spec: image: busybox Pod Manifest How event triggering happens?
- 33. Demo Picture Credits: AshleyMcNamara
- 34. Demo ● nodeSelector ● nodeAffinity ●podAffinity ● taints and tolerations
- 35. What else? ● Extensible,https://kubernetes.io/docs/reference/command-line-tools-reference/kube-scheduler/ ● Custom Scheduler, https://kubernetes.io/docs/tasks/administer-cluster/configure-multiple-schedulers/ ● Even Pod Spreading, https://github.com/kubernetes/enhancements/blob/master/keps/sig- scheduling/20190221-even-pods-spreading.md ● Scheduling Framework, https://github.com/kubernetes/enhancements/blob/master/keps/sig- scheduling/20180409-scheduling-framework.md ● Batch Scheduling https://github.com/kubernetes/enhancements/blob/master/keps/sig-scheduling/34-20180703- coscheduling.md
- 36. References ● Kubernetes CommunityDocs ● https://jvns.ca/blog/2017/07/27/how-does-the-kubernetes-scheduler-work/ ● What Happens when k8s
- 37. Getting Involved ➔ GithubRepo https://github.com/kubernetes/kubernetes/tree/master/pkg/s cheduler ➔ Mailing List: kubernetes-sig-scheduling https://groups.google.com/forum/#!forum/kubernetes-sig- scheduling ➔ Slack: #sig-scheduling https://kubernetes.slack.com/messages/C8TSNPY4T
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