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

by d-kuro

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

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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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Controller ʹ͍ͭͯ

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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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͓͠·͍