How to manage stateful applications in Kubernetes

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How to manage stateful applications in Kubernetes Devoxx France - 2018 1

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Florian Woerner DevOps Engineer / Cloud Architect Onmyown @woernfl florian.woerner@onmyown.io 2

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Agenda ● Context ● Volume provider ● Volumes lifecycle management ● Demo ● Conclusion 3 @woernfl

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Why should I choose Kubernetes over VMs? 4 @woernfl

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Because Kubernetes is a distributed system management framework 5

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Why would we need to manage data persistence? 6 @woernfl

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Because, stateless architecture… it does not exist 7

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Types of volumes 8

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Types of Volumes - Kubernetes Internals ● configMap ● downwardAPI ● emptyDir ● gitRepo ● hostPath ● local ● persistentVolumeClaim ● projected ● Secret ● csi 9 @woernfl

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Types of Volumes - Public Cloud 10 @woernfl ● awsElasticBlockStore ● azureDisk ● azureFile ● gcePersistentDisk

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Types of Volumes - Non Cloud Dependant ● cephfs ● fc (fibre channel) ● flocker ● glusterfs ● nfs ● iscsi ● portworxVolume ● quobyte ● rbd (Rados Block Device) ● scaleIO ● storageos ● vsphereVolume 11 @woernfl

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Any issues? 12 @woernfl

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CSI to the rescue 13

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What is CSI? ● Container Storage Interface ● Adopted by Kubernetes, Mesos and Cloud Foundry (for the moment) ● Supported as beta in Kubernetes 1.10 (planed to fall in stable for 1.12) ● Is a standardized way of exposing storage to a container 14 @woernfl

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Why is it so important? ● Common interface to multiple platforms (standardisation) ● Allow storage provider to release out of tree 15 @woernfl

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Real world scenario with Bob the dev and John the Sysadmin 16

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Scenario: Persistent Volumes and Claims 17

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Scenario: Persistent Volumes and Claims 18 @woernfl Kubernetes Node Storage (NFS, EBS, ...)

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Scenario: Persistent Volumes and Claims 19 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume

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Scenario: Persistent Volumes and Claims 20 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume Persistent Volume Claim

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Scenario: Persistent Volumes and Claims 21 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume Persistent Volume Claim Pod

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Scenario: Persistent Volumes and Claims 22 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume Persistent Volume Claim Pod

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Scenario: Dynamic Provisioning 23

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Scenario: Dynamic Provisioning 24 @woernfl Kubernetes Node Storage (NFS, EBS, ...)

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Scenario: Dynamic Provisioning 25 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Storage Class - SDD Storage Class - HDD

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Scenario: Dynamic Provisioning 26 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume Claim Storage Class - SDD Storage Class - HDD

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Scenario: Dynamic Provisioning 27 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume Persistent Volume Claim Storage Class - SDD Storage Class - HDD

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Scenario: Dynamic Provisioning 28 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume Persistent Volume Claim Pod Storage Class - SDD Storage Class - HDD

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Scenario: Dynamic Provisioning 29 @woernfl Kubernetes Node Storage (NFS, EBS, ...) Persistent Volume Persistent Volume Claim Pod Storage Class - SDD Storage Class - HDD

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Demo 30

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Conclusion 31

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References 32 ● Volumes Kubernetes Doc: https://kubernetes.io/docs/concepts/storage/volumes/ ● Kubernetes Tasks: https://kubernetes.io/docs/tasks/ ● Configure a Pod to Use a PersistentVolume for Storage: https://kubernetes.io/docs/tasks/configure-pod-container/configure-persistent-volume-storage/ ● Run a Single-Instance Stateful Application: https://kubernetes.io/docs/tasks/run-application/run-single-instance-stateful-application/ ● Run a Replicated Stateful Application: https://kubernetes.io/docs/tasks/run-application/run-replicated-stateful-application/ ● StatefulSets Kubernetes Doc: https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/ @woernfl

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Thank you! 33 Link to the repos: https://github.com/woernfl/k8s-stateful-demo