Kubernetes Cluster Upgrade / Mercari Meetup for Microservices Platform

https://mercari.connpass.com/event/92168/

Transcript

1. 2018/07/19
   Mercari Meetup for Microservices Platform
   @dtan4
   Kubernetes Cluster Upgrade
   

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2. 2
   About me
   @dtan4 (Daisuke Fujita)
   SRE @ Mercari, Inc. Microservices Platform Team
   

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3. 3
   Topics
   ● Why we have to upgrade Kubernetes cluster?
   ● How to upgrade Kubernetes cluster safely?
   ● Case: Upgrade GKE clusters in Mercari
   

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4. Why we have to upgrade Kubernetes
   cluster?
   

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5. 5
   Kubernetes Release Versioning
   ● Minor releases happens approximately every 3 months
   v1.11.0 2018-06-28 05:06:28 +0900 JST
   v1.10.0 2018-03-27 01:41:58 +0900 JST
   v1.9.0 2017-12-16 05:53:13 +0900 JST
   v1.8.0 2017-09-29 07:13:57 +0900 JST
   v1.7.0 2017-06-30 07:53:16 +0900 JST
   https://github.com/kubernetes/community/blob/6e31a546a50f6f57f3e9e1422ade0599f5e3e77d/contributors/design-proposals/release/versioning.md#supported-releases-and-component-skew
   

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6. 6
   Kubernetes Release Versioning
   ● 3 minor versions are supported
   v1.11.0 2018-06-28 05:06:28 +0900 JST
   v1.10.0 2018-03-27 01:41:58 +0900 JST
   v1.9.0 2017-12-16 05:53:13 +0900 JST
   v1.8.0 2017-09-29 07:13:57 +0900 JST
   v1.7.0 2017-06-30 07:53:16 +0900 JST
   https://github.com/kubernetes/community/blob/6e31a546a50f6f57f3e9e1422ade0599f5e3e77d/contributors/design-proposals/release/versioning.md#supported-releases-and-component-skew
   

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7. 7
   Security fixes
   

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8. 8
   Kubernetes new features
   ● Pod priority and preemption
   ● CRD versioning
   ● HPA with custom metrics
   ● ...
   

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9. 9
   3rd party integrations
   

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10. How to upgrade Kubernetes cluster safely?
    

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11. 11
    kubectl cordon
    ● Mark node as Pod-unschedulable
    ○ e.g., kubectl cordon node-02
    node-01
    Pod
    Pod
    Pod
    node-02
    Pod
    Pod
    new Pod
    ❌
    node-03
    Pod
    Pod
    SchedulingDisabled
    

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12. 12
    kubectl drain
    ● kubectl cordon + Evict Pods on the node gracefully
    ○ e.g., kubectl drain node-02
    node-01
    Pod
    Pod
    Pod
    node-02
    Pod
    Pod
    new Pod
    ❌
    node-03
    Pod
    Pod
    Pod Pod
    SchedulingDisabled
    

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13. 13
    Availability?
    ● All ‘C’ Pods are running on the same node
    node-01
    A
    A
    B
    node-02 node-03
    B
    A
    C
    C
    C
    

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14. 14
    Availability?
    ● kubectl drain node-02
    ○ All ‘C’ Pods will be terminated simultaneously
    node-01
    A
    A
    B
    node-02
    C
    C
    node-03
    B
    A
    C C
    SchedulingDisabled
    C C
    

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15. 15
    PodDisruptionBudget
    ● PodDisruptionBudget (PDB) limits the number of Pods of a
    replicated application that are down simultaneously from
    voluntary disruptions (e.g., drain, autoscaling)
    ● work well with Deployment or Replicaset
    ● Specify minAvailable or maxAvailable by the number of
    Pods or percentage
    ● Application must be running on multiple Pods
    https://kubernetes.io/docs/concepts/workloads/pods/disruptions/
    

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16. 16
    PodDisruptionBudget example
    apiVersion: policy/v1beta1
    kind: PodDisruptionBudget
    metadata:
    name: app-c
    namespace: app-c-dev
    spec:
    minAvailable: 50%
    selector:
    matchLabels:
    app: c
    

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17. 17
    PDB + kubectl drain
    ● PDB for C: minAvailable: 50% (ALLOWED DISRUPTIONS: 1)
    node-01
    A
    A
    B
    node-02 node-03
    B
    A
    C
    C
    C
    

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18. 18
    PDB + kubectl drain
    ● PDB for C: minAvailable: 50% (ALLOWED DISRUPTIONS: 1)
    ● kubectl drain node-02 keeps at least two ‘C’ Pods available
    node-01
    A
    A
    B
    node-02
    C
    node-03
    B
    A
    C
    SchedulingDisabled
    C
    C
    

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19. 19
    PDB + kubectl drain
    node-01
    A
    A
    B
    node-02
    C
    node-03
    B
    A
    C C
    SchedulingDisabled
    C
    ● PDB for C: minAvailable: 50% (ALLOWED DISRUPTIONS: 1)
    ● kubectl drain node-02 keeps at least two ‘C’ Pods available
    

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20. 20
    PDB + kubectl drain
    node-01
    A
    A
    B
    node-02 node-03
    B
    A
    C C
    SchedulingDisabled
    C C
    ● PDB for C: minAvailable: 50% (ALLOWED DISRUPTIONS: 1)
    ● kubectl drain node-02 keeps at least two ‘C’ Pods available
    

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21. 21
    GKE cluster upgrade
    1. Upgrade GKE master
    2. Upgrade GKE nodes
    ○ Rolling update existing nodes
    ○ Node pools migration
    

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22. 22
    Upgrade GKE master
    ● Zonal (single master) cluster causes control plane downtime
    ○ ~ 2 minutes
    ○ kubectl stops working
    ○ CronJob will not be kicked
    ● Regional (HA masters) cluster can be upgrade with
    zero-downtime
    ○ Existing zonal -> regional migration is not supported...
    

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23. 23
    GKE node upgrade: rolling update
    ● Upgrade existing nodes one by one
    ● Behavior of “Automatic node upgrades”
    ● Make sure that cluster capacity is enough even 1 node is down
    node-01 v1.10 node-02 v1.10 node-03 v1.10
    node-01 v1.11 node-02 v1.10 node-03 v1.10
    

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24. 24
    GKE node upgrade: node pools migration
    ● Create new node pools with new Kubernetes version
    ● Migrate all Pods on old nodes to new nodes
    ○ kubectl cordon
    ○ kubectl drain
    ● Delete old node pools
    ● Make sure that enough GCP resource capacity is prepared
    https://cloudplatform.googleblog.com/2018/06/Kubernetes-best-practices-upgrading-your-clusters-with-zero-downtime.html
    

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25. 25
    nodepool-1-10 v1.10
    GKE node upgrade: node pools migration
    node-1-10-a v1.10
    node-1-10-b v1.10
    node-1-10-c v1.10
    

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26. 26
    nodepool-1-10 v1.10
    GKE node upgrade: node pools migration
    node-1-10-a v1.10
    node-1-10-b v1.10
    node-1-10-c v1.10
    nodepool-1-11 v1.11
    node-1-11-a v1.11
    node-1-11-b v1.11
    node-1-11-c v1.11
    

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27. 27
    nodepool-1-10 v1.10
    GKE node upgrade: node pools migration
    node-1-10-a v1.10
    node-1-10-b v1.10
    node-1-10-c v1.10
    nodepool-1-11 v1.11
    node-1-11-a v1.11
    node-1-11-b v1.11
    node-1-11-c v1.11
    SchedulingDisabled
    SchedulingDisabled
    SchedulingDisabled
    

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28. 28
    nodepool-1-10 v1.10
    GKE node upgrade: node pools migration
    node-1-10-a v1.10
    node-1-10-b v1.10
    node-1-10-c v1.10
    nodepool-1-11 v1.11
    node-1-11-a v1.11
    node-1-11-b v1.11
    node-1-11-c v1.11
    SchedulingDisabled
    SchedulingDisabled
    SchedulingDisabled
    

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29. 29
    nodepool-1-10 v1.10
    GKE node upgrade: node pools migration
    node-1-10-a v1.10
    node-1-10-b v1.10
    node-1-10-c v1.10
    nodepool-1-11 v1.11
    node-1-11-a v1.11
    node-1-11-b v1.11
    node-1-11-c v1.11
    SchedulingDisabled
    SchedulingDisabled
    SchedulingDisabled
    

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30. 30
    GKE node upgrade: node pools migration
    nodepool-1-11 v1.11
    node-1-11-a v1.11
    node-1-11-b v1.11
    node-1-11-c v1.11
    

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31. Case: GKE cluster upgrade in Mercari
    

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32. 32
    Case: GKE cluster upgrade in Mercari
    1. Codenize GKE resources
    2. Create PDBs for all microservices
    3. Upgrade!
    a. Upgrade GKE master (Terraform)
    b. Create GKE node pools (Terraform)
    c. Migrate all Pods (script)
    d. Delete old GKE node pools (Terraform)
    

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33. 33
    Codenize GKE resources
    ● Existing GKE clusters were created by gcloud command
    ● We want to manage GKE (and all other cloud) resources on
    GitHub!
    ○ git log as operation history
    ○ review changes by other team members
    ○ modify resources from CI without manual operation
    

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34. 34
    Codenize GKE resources
    ● Codenize GKE resources by dtan4/terraforming-gke
    

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35. 35
    Create PDBs for all microservices
    ● Most of our microservices didn’t have PDBs
    ● Define default minAvailable by SREs
    ● Confirm microservices’ availability with developers
    

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36. 36
    Upgrade GKE master
    ● Modify Terraform code
    ● Review by team members
    ● Apply on CircleCI
    

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37. 37
    Upgrade GKE master
    

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38. 38
    Create & Delete GKE node pools
    ● Copy-and-paste & modify Terraform code
    ● Review by team members
    ● Apply on CircleCI
    

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39. 39
    Future work
    ● Enable “Automatic node upgrades”
    ○ ensure all microservices are resilient towards disruptions
    ○ reduce upgrade steps
    ● Create PDB by microservice developers themselves
    

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