Kubernetes のソースコードとの付き合い方 #gounco / Kubernetes source code reading

Go(Un)Conference（Goあんこ）LT大会 6kg で発表した資料です
https://gounconference.connpass.com/event/129090/

Transcript

1. Kubernetes ͷ
   ιʔείʔυͱͷ
   ෇͖߹͍ํ
   19/05/27 Go(Un)ConferenceʢGo͋Μ͜ʣLTେձ 6kg

   @ponde_m
   

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3. ࠓ೔࿩͢͜ͱ
   • Kubernetes ͷΞʔΩςΫνϟʹ͍ͭͯ
   • Kubernetes ͷιʔείʔυΛಡΉࡍʹ

   ໾ʹཱͭ࿩
   Go ͷษڧձ͚ͩͲ Kubernetes ͱ͸ͳΜͧ΍

   Έ͍ͨͳ࿩͕݁ߏ͋Γ·͢ (Gopher ͘Μ͸͍ͬͺ͍ग़·͢)
   

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4. Kubernetes ͱ͸
   

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5. Kubernetes ͱ͸
   • ίϯςφΛಈ͔ͨ͢ΊͷϓϥοτϑΥʔϜ
   • ίϯςφΛ͍͍ײ͡ʹӡ༻͢ΔͨΊͷػೳΛ
   ͍ͬͺ͍͍࣋ͬͯΔ
   • σϓϩΠ, εέʔϦϯά, ࣗݾम෮ etc…
   k8s ͬͯॻ͔ΕͨΓ͢Δͷ͸

   Kubernetes ͕ (k + 8 จࣈ + s) ͔ͩΒ
   

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6. Kubernetes ͷ

   ΞʔΩςΫνϟ
   

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7. • ΞʔΩςΫνϟʹ͍ͭͯཧղ͢Δͱ,

   ࣗ෼ͷಡΈ͍ͨ෦෼ͷίʔυ͕

   Ͳͷίϯϙʔωϯτʹ͋Δͷ͔Θ͔Δ
   • ͦΕͧΕͷίϯϙʔωϯτͱ

   ͦͷ੹຿ʹ͍ͭͯཧղ͠Α͏
   Kubernetes ͷΞʔΩςΫνϟ
   ࣍ͷϖʔδ͔Βͬ͘͟Γͱ

   ਤΛ༻͍ͯઆ໌͠·͢
   

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8. Kubernetes ͷΞʔΩςΫνϟ
   Master
   Node
   Node
   API
   API
   

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9. Kubernetes ͷΞʔΩςΫνϟ
   Master
   Node
   Node
   API
   API
   

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10. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    Contoroller

    Manager
    Scheduler
    etcd
    

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11. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    Contoroller

    Manager
    Scheduler
    etcd
    API Server
    Kubernetes ͷ ϦιʔεΛ؅ཧ͢Δ API Server
    શͯͷϦιʔεૢ࡞͸ API Server Λܦ༝ͯ͠ߦ͏
    

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12. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    Contoroller

    Manager
    Scheduler
    etcd
    Contoroller

    Manager
    API Server Ͱ͸Ϧιʔε৘ใͷ CRUD ͙Β͍͔͠ߦͳͬͯ
    ͓ΒͣɺϦιʔεʹର͢Δ࣮ࡍͷॲཧͷத਎͸ Controller
    ͱݺ͹ΕΔίϯϙʔωϯτ͕ඇಉظͰߦͳ͍ͬͯΔ
    Controller (goroutine)
    Controller (goroutine)
    Controller (goroutine)
    ىಈ
    

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13. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    Contoroller

    Manager
    Scheduler
    etcd
    Scheduler
    Pod (ίϯςφ) Λϊʔυ΁ׂΓ౰ͯΔ
    

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14. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    Contoroller

    Manager
    Scheduler
    etcd
    ϦιʔεͷӬଓԽʹ࢖ΘΕΔ෼ࢄ KVS
    etcd
    

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15. Kubernetes ͷΞʔΩςΫνϟ
    Master
    Node
    Node
    API
    API
    

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16. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    kube-proxy
    Pod
    Pod
    Pod
    Internet
    kubelet
    

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17. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    kubelet kube-proxy
    Pod
    Pod
    Pod
    Internet
    kubelet
    ֤ϊʔυͰಈ࡞͢Δ
    Pod Λىಈ, ؅ཧ͢ΔΤʔδΣϯτ
    kubelet
    

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18. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    kube-proxy
    Pod
    Pod
    Pod
    Internet
    kube-proxy
    kubelet
    ֤ϊʔυͰಈ࡞͢Δ
    Service ͷఆٛΛݩʹϧʔςΟϯά
    ͯ͘͠ΕΔωοτϫʔΫϓϩΩγ
    kube-proxy
    

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19. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    kube-proxy
    Pod
    Pod
    Pod
    Internet
    Pod
    Pod
    Pod
    kubelet
    Container Runtime
    Docker Ҏ֎΋ಈ͘
    Pod
    Pod
    Pod
    

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20. Kubernetes ͷ
    ιʔείʔυʹ͍ͭͯ
    

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21. Kubernetes ͷιʔείʔυʹ͍ͭͯ
    • github.com/kubernetes/kubernetes
    • Go Modules ରԠͯ͠ΔͷͰ go mod ίϚϯ
    υΛ࣮ߦ͢ΔͱϏϧυͰ͖ΔΑ͏ʹͳΔ
    • ಡΉ࣌͸ IDE ͰίʔυδϟϯϓΛ࢖͓͏
    4݄͙Β͍ʹ Go Modules ରԠͨ͠

    https://github.com/kubernetes/kubernetes/pull/74877
    

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22. Kubernetes ͷιʔείʔυʹ͍ͭͯ
    • ϒϥ΢β͔Β௥͏࣌͸ SourceGraph Λ

    ೖΕΔͱศར
    • ϒϥ΢β͔Β Code Jump Ͱ͖Δ
    • https://about.sourcegraph.com/
    

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23. Kubernetes ͷιʔείʔυʹ͍ͭͯ
    • Kubernetes ͷίϯϙʔωϯτͷ࣮૷Ͱ͸

    github.com/spf13/cobra ͕࢖ΘΕ͍ͯΔ
    • Server ͱͯ͠ৼΔ෣͏΋ͷ΋ cobra Ͱ࣮૷͞Ε͍ͯΔ
    • ࣮ߦ࣌ͷ Option ͰύϥϝʔλΛ౉ͨ͠ΓͰ͖Δ
    

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24. main package ͸
    Ͳ͜ʹ͋Δͷ͔
    

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25. main package ͸Ͳ͜ʹ͋Δͷ͔
    • cmd package ͷதΛݟΔͱ֤ίϯϙʔωϯτ͝
    ͱʹ͞Βʹ package ͕෼͔Ε͍ͯΔ
    

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26. github.com/kubernetes/
    kubernetes/cmd/
    ͖ͬ͞ݟͨΑ͏ͳ໊લ͕ͪΒ΄Β
    

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27. • main package ͸ͦͷ഑Լʹ͋Δ
    main package ͸Ͳ͜ʹ͋Δͷ͔
    

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29. Controller ʹ͍ͭͯ
    

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30. Kubernetes ͷΞʔΩςΫνϟ
    API Server
    Contoroller

    Manager
    Scheduler
    etcd
    Contoroller

    Manager
    API Server Ͱ͸Ϧιʔε৘ใͷ CRUD ͙Β͍͔͠ߦͳͬͯ
    ͓ΒͣɺϦιʔεʹର͢Δ࣮ࡍͷॲཧͷத਎͸ Controller
    ͱݺ͹ΕΔίϯϙʔωϯτ͕ඇಉظͰߦͳ͍ͬͯΔ
    Controller (goroutine)
    Controller (goroutine)
    Controller (goroutine)
    ىಈ
    ͓͞Β͍
    

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31. • Ϧιʔεʹର͢Δ࣮ࡍͷॲཧͷத਎͸ Controller ͱݺ͹ΕΔί
    ϯϙʔωϯτ͕ඇಉظͰߦͳ͍ͬͯΔ
    • ྫ͑͹ Deployment ͷಈ͖ͷ࣮૷͕ݟ͍ͨʂ

    ͬͯͳͬͨ࣌ʹ API Server ͷίʔυΛಡΈʹߦͬͯ΋

    Կ΋ॻ͍ͯͳ͍
    • Controller Λಡ΋͏
    Controller ʹ͍ͭͯ
    ͜ͷ͜ͱΛ஌Βͣʹ࠷ॳ API Server ͷίʔυಡΜͰ·ͨ͠
    

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32. Controller ʹ͍ͭͯ
    Contoroller

    Manager
    Controller (goroutine)
    Controller (goroutine)
    Controller (goroutine)
    ىಈ
    • ࣮ࡍʹͲΜͳײ͡ͳͷ͔ίʔυͰݟͯΈΔ
    

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33. ͜Μͳײ͡ͷ map Ͱఆٛ͞Ε͍ͯΔ
    https://github.com/kubernetes/kubernetes/blob/v1.14.2/
    cmd/kube-controller-manager/app/
    controllermanager.go#L341-L384
    

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34. Controller ͷ໊લͱ
    Controller Λ࣮ߦ͢ΔͨΊͷؔ਺
    

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35. func StartControllers() Ͱ Controller ΛൃՐ
    (ΊͬͪΌίʔυ࡟ͬͯΔ)
    https://github.com/kubernetes/kubernetes/blob/v1.14.2/
    cmd/kube-controller-manager/app/
    controllermanager.go#L461-L501
    

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36. ͖ͬ͞ͷ map Λ for Ͱճͯ͠
    ͜͜Ͱ Controller ͷ࣮ߦؔ਺ΛݺΜͰΔ
    

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37. ྫͱͯ͠ Deployment ͷ Controller ͷ࣮ߦؔ਺
    https://github.com/kubernetes/kubernetes/blob/v1.14.2/
    cmd/kube-controller-manager/app/apps.go#L82-L97
    

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38. ίϯετϥΫλͰ Controller Λ࡞ͬͯ
    goroutine Ͱ Controller Λ࣮ߦ
    

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39. ·ͱΊ
    • Kubernetes ͷΞʔΩςΫνϟ͸

    ͓֮͑ͯ͘ͱ໾ʹཱͭ
    • Kubernetes ͷιʔείʔυ͸ҙ֎ʹಡΊΔ
    • Go ͸ಡΈ΍͍͢
    ΈΜͳ΋ಡ΋͏
    

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40. ͓·͚
    

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41. ໾ʹཱͭϦϯΫͱ͔
    • github.com/jamiehannaford/what-happens-when-k8s
    • Kubernetes ͕ىಈ͔ͯ͠ΒͲΜͳ͜ͱΛ͍ͯ͠Δ͔

    ιʔείʔυϨϕϧͰղઆͯ͘͠ΕΔ
    • ͳΜͱ೔ຊޠ ver ΋͋Δ
    • ιʔείʔυͷϦϯΫ͕ݹ͔ͬͨΓ, ϦϯΫ੾Εͩͬͨ
    Γ͢ΔͷͰ PR Λग़ͦ͏! (ग़ͯ͠Δ)
    

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42. ໾ʹཱͭϦϯΫͱ͔
    • https://gopherize.me/
    • Զ͚ͩͷ࠷ߴʹ͔Θ͍͍ Gopher ܅Λ࡞ΕΔαΠτ
    

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43. ͓͠·͍
    

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