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

Transcript

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

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   None
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   ࠓ೔࿩͢͜ͱ • Kubernetes ͷΞʔΩςΫνϟʹ͍ͭͯ • Kubernetes ͷιʔείʔυΛಡΉࡍʹ
 ໾ʹཱͭ࿩ Go ͷษڧձ͚ͩͲ

   Kubernetes ͱ͸ͳΜͧ΍
 Έ͍ͨͳ࿩͕݁ߏ͋Γ·͢ (Gopher ͘Μ͸͍ͬͺ͍ग़·͢)
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   Kubernetes ͱ͸

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   Kubernetes ͱ͸ • ίϯςφΛಈ͔ͨ͢ΊͷϓϥοτϑΥʔϜ • ίϯςφΛ͍͍ײ͡ʹӡ༻͢ΔͨΊͷػೳΛ ͍ͬͺ͍͍࣋ͬͯΔ • σϓϩΠ, εέʔϦϯά,

   ࣗݾम෮ etc… k8s ͬͯॻ͔ΕͨΓ͢Δͷ͸
 Kubernetes ͕ (k + 8 จࣈ + s) ͔ͩΒ
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   Kubernetes ͷ
 ΞʔΩςΫνϟ

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   • ΞʔΩςΫνϟʹ͍ͭͯཧղ͢Δͱ,
 ࣗ෼ͷಡΈ͍ͨ෦෼ͷίʔυ͕
 Ͳͷίϯϙʔωϯτʹ͋Δͷ͔Θ͔Δ • ͦΕͧΕͷίϯϙʔωϯτͱ
 ͦͷ੹຿ʹ͍ͭͯཧղ͠Α͏ Kubernetes ͷΞʔΩςΫνϟ ࣍ͷϖʔδ͔Βͬ͘͟Γͱ


   ਤΛ༻͍ͯઆ໌͠·͢
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   Kubernetes ͷΞʔΩςΫνϟ Master Node Node API API

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   Kubernetes ͷΞʔΩςΫνϟ Master Node Node API API

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    Kubernetes ͷΞʔΩςΫνϟ API Server Contoroller
 Manager Scheduler etcd

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    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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    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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    Kubernetes ͷΞʔΩςΫνϟ API Server Contoroller
 Manager Scheduler etcd Scheduler Pod

    (ίϯςφ) Λϊʔυ΁ׂΓ౰ͯΔ
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    Kubernetes ͷΞʔΩςΫνϟ API Server Contoroller
 Manager Scheduler etcd ϦιʔεͷӬଓԽʹ࢖ΘΕΔ෼ࢄ KVS

    etcd
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    Kubernetes ͷΞʔΩςΫνϟ Master Node Node API API

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

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

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

    kubelet ֤ϊʔυͰಈ࡞͢Δ Service ͷఆٛΛݩʹϧʔςΟϯά ͯ͘͠ΕΔωοτϫʔΫϓϩΩγ kube-proxy
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    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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    Kubernetes ͷ ιʔείʔυʹ͍ͭͯ

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    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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    Kubernetes ͷιʔείʔυʹ͍ͭͯ • ϒϥ΢β͔Β௥͏࣌͸ SourceGraph Λ
 ೖΕΔͱศར • ϒϥ΢β͔Β Code

    Jump Ͱ͖Δ • https://about.sourcegraph.com/
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    Kubernetes ͷιʔείʔυʹ͍ͭͯ • Kubernetes ͷίϯϙʔωϯτͷ࣮૷Ͱ͸
 github.com/spf13/cobra ͕࢖ΘΕ͍ͯΔ • Server ͱͯ͠ৼΔ෣͏΋ͷ΋

    cobra Ͱ࣮૷͞Ε͍ͯΔ • ࣮ߦ࣌ͷ Option ͰύϥϝʔλΛ౉ͨ͠ΓͰ͖Δ
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    main package ͸ Ͳ͜ʹ͋Δͷ͔

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

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

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    • main package ͸ͦͷ഑Լʹ͋Δ main package ͸Ͳ͜ʹ͋Δͷ͔

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    None
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    Controller ʹ͍ͭͯ

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    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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    • 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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    Controller ʹ͍ͭͯ Contoroller
 Manager Controller (goroutine) Controller (goroutine) Controller (goroutine)

    ىಈ • ࣮ࡍʹͲΜͳײ͡ͳͷ͔ίʔυͰݟͯΈΔ
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    ͜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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    Controller ͷ໊લͱ Controller Λ࣮ߦ͢ΔͨΊͷؔ਺

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    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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    ͖ͬ͞ͷ map Λ for Ͱճͯ͠ ͜͜Ͱ Controller ͷ࣮ߦؔ਺ΛݺΜͰΔ

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    ྫ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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    ίϯετϥΫλͰ Controller Λ࡞ͬͯ goroutine Ͱ Controller Λ࣮ߦ

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    ·ͱΊ • Kubernetes ͷΞʔΩςΫνϟ͸
 ͓֮͑ͯ͘ͱ໾ʹཱͭ • Kubernetes ͷιʔείʔυ͸ҙ֎ʹಡΊΔ • Go

    ͸ಡΈ΍͍͢ ΈΜͳ΋ಡ΋͏
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    ͓·͚

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

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    ͓͠·͍