図で理解する Descheduler #k8sjp #ymju / Introduction to Descheduler

Kubernetes Meetup Tokyo 19 (Yahoo! JAPAN MEETUP共催) で発表した資料です
https://k8sjp.connpass.com/event/126207/

Transcript

1. ਤͰཧղ͢Δ Descheduler 19/05/31 Kubernetes Meetup Tokyo #19 / Yahoo! JAPAN MEETUP #32
 @ponde_m
3. Descheduler ? ?
4. Scheduler ͷ͓͞Β͍
5. Kubernetes ͷΞʔΩςΫνϟ API Server Contoroller
 Manager Scheduler etcd
6. Kubernetes ͷΞʔΩςΫνϟ API Server Contoroller
 Manager Scheduler etcd Scheduler Pod Λ Node ΁ׂΓ౰ͯΔ Scheduler
7. Scheduler • Pod ͷ࡞੒࣌ʹεέδϡʔϦϯάΛߦ͏ • Kubernetes Ϋϥελ͸ಈతʹมԽ͢Δ • Node ͷϦιʔεʹภΓ͕ग़Δ • taints, label ͕มߋ͞Εͯ΋
 εέδϡʔϦϯά͞Εͨ Pod ͸ͦͷ·· • Node ͕૿͑ͯ΋εέδϡʔϦϯά͞Εͨ Pod ͸ͦͷ·· • Node Ͱো֐͕ൃੜ͠, 
 Pod ͕ଞͷ Node ʹҠಈͨ͋͠ͱͦͷ··
8. Scheduler • Pod ͷ࡞੒࣌ʹεέδϡʔϦϯάΛߦ͏ • Kubernetes Ϋϥελ͸ಈతʹมԽ͢Δ • Node ͷϦιʔεʹภΓ͕ग़Δ • taints, label ͕มߋ͞Εͯ΋
 εέδϡʔϦϯά͞Εͨ Pod ͸ͦͷ·· • Node ͕૿͑ͯ΋εέδϡʔϦϯά͞Εͨ Pod ͸ͦͷ·· • Node Ͱো֐͕ൃੜ͠, 
 Pod ͕ଞͷ Node ʹҠಈͨ͋͠ͱͦͷ·· • Kubernetes Ϋϥελ͸ಈతʹมԽ͢Δ • Node ͷϦιʔεʹภΓ͕ग़Δ • taints, label ͕มߋ͞Εͯ΋
 εέδϡʔϦϯά͞Εͨ Pod ͸ͦͷ·· • Node ͕૿͑ͯ΋εέδϡʔϦϯά͞Εͨ Pod ͸ͦͷ·· • Node Ͱো֐͕ൃੜ͠, 
 Pod ͕ଞͷ Node ʹҠಈͨ͋͠ͱͦͷ·· Pod ͷ࡞੒࣌ʹ͔͠
 εέδϡʔϦϯά
 ͯ͘͠Εͳ͍ͷͰ
 ͜ͷΑ͏ͳ໰୊͕ग़ͯ͘Δ
9. Node Node Node * 2
10. Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod ֤ϊʔυʹಉ͡ Pod ͕ 6 ͭ
11. Node Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod NEW!!
12. Node Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Node طʹ Node ʹ
 εέδϡʔϦϯά͞Ε͍ͯΔ Pod ͸Ҡಈͯ͘͠Εͳ͍
13. Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod Pod ͜͏ͳͬͯ΄͍͠
14. Descheduler
15. Descheduler • github.com/kubernetes-incubator/descheduler • ҠಈՄೳͳ Pod Λݟ͚ͭͯ࡟আͯ͘͠ΕΔ • ࠶εέδϡʔϧ͸ Scheduler ͕ߦ͏ • Kubernetes ͷ Job ͱ࣮ͯ͠ߦͤ͞Δ
16. Descheduler • github.com/kubernetes-incubator/descheduler • ҠಈՄೳͳ Pod Λݟ͚ͭͯ࡟আͯ͘͠ΕΔ • ࠶εέδϡʔϧ͸ Scheduler ͕ߦ͏ • Kubernetes ͷ Job ͱ࣮ͯ͠ߦͤ͞Δ ҠಈՄೳͳ Pod ର৅ͷ Pod Λ Ͳ͏΍ܾͬͯΊΔͷ͔
17. Policy and Strategies • Descheduler Ͱ͸, ࡟আ͢Δ Pod ͷϙϦγʔΛ
 ϑΝΠϧͰఆٛ͢Δ • 4 ͭͷετϥςδΛ૊Έ߹Θͤͯઃఆ͢Δ • RemoveDuplicates • LowNodeUtilization • RemovePodsViolatingInterPodAntiAffinity • RemovePodsViolatingNodeAffinity
18. RemoveDuplicates Pod Pod Pod • Replica Set / Replication Controller / Deployment / Job
 ʹඥ͍͍ͮͯΔ Pod ͕֤ Node Ͱ 1 ͚ͭͩͰ͋Δ͜ͱΛ֬ೝ͢Δ • ෳ਺഑ஔ͞ΕͯͨΒ࡟আ͢Δ
19. RemoveDuplicates Pod Pod Pod
20. RemoveDuplicates Pod Pod Pod Pod ͕
 ଞͷ Node ʹҠಈ
21. RemoveDuplicates Pod Pod Node Pod Node ͕ੜ͖ฦͬͯ΋
 Pod ͸໭ͬͯ͜ͳ͍
22. RemoveDuplicates Pod Pod Pod Pod ͕
 ࠶εέδϡʔϦϯά͞ΕΔ Pod Run Descheduler
23. LowNodeUtilization • Ϧιʔεͷ࢖༻཰͕௿͍ Node ΁
 Ϧιʔεͷ࢖༻཰͕ߴ͍ Node ͔Β
 Pod Λ࠶εέδϡʔϧ͢Δ͜ͱΛ໨తͱ͍ͯ͠Δ • Pod ͷ Resource requests ͕ܭࢉʹ༻͍ΒΕΔ • thresholds ʹઃఆͨ͠ᮢ஋ΛԼճΔͱ
 Node ͷϦιʔε࢖༻཰͕௿͍ͱΈͳ͞ΕΔ • targetThresholds ʹઃఆͨ͠ᮢ஋Λ্ճΔͱ
 Node ͷϦιʔε࢖༻཰͕ߴ͍ͱΈͳ͞ΕΔ
24. LowNodeUtilization • Ϧιʔεͷ࢖༻཰͕௿͍ Node ΁
 Ϧιʔεͷ࢖༻཰͕ߴ͍ Node ͔Β
 Pod Λ࠶εέδϡʔϧ͢Δ • thresholds ʹઃఆͨ͠ᮢ஋ΛԼճΔͱ
 Node ͷϦιʔε࢖༻཰͕௿͍ͱΈͳ͞ΕΔ • targetThresholds ʹઃఆͨ͠ᮢ஋Λ্ճΔͱ
 Node ͷϦιʔε࢖༻཰͕ߴ͍ͱΈͳ͞ΕΔ • thresholds ʹઃఆͨ͠ᮢ஋ΛԼճΔͱ
 Node ͷϦιʔε࢖༻཰͕௿͍ͱΈͳ͞ΕΔ CPU / RAM / Pod ਺ ͷᮢ஋
 ԼճΔͱϦιʔε࢖༻཰͕௿͍ Node ͱ൑ఆ͞ΕΔ
25. LowNodeUtilization • Ϧιʔεͷ࢖༻཰͕௿͍ Node ΁
 Ϧιʔεͷར༻཰͕ߴ͍ Node ͔Β
 Pod Λ࠶εέδϡʔϧ͢Δ • thresholds ʹઃఆͨ͠ᮢ஋ΛԼճΔͱ
 Node ͷϦιʔε࢖༻཰͕௿͍ͱΈͳ͞ΕΔ • targetThresholds ʹઃఆͨ͠ᮢ஋Λ্ճΔͱ
 Node ͷϦιʔε࢖༻཰͕ߴ͍ͱΈͳ͞ΕΔ CPU / RAM / Pod ਺ ͷᮢ஋
 ্ճΔͱϦιʔε࢖༻཰͕ߴ͍ Node ͱ൑ఆ͞ΕΔ • targetThresholds ʹઃఆͨ͠ᮢ஋Λ্ճΔͱ
 Node ͷϦιʔε࢖༻཰͕ߴ͍ͱΈͳ͞ΕΔ
26. LowNodeUtilization Pod Pod Pod Pod Pod Pod thresholds: “pods": 2 targetThresholds: “pods”: 2
27. LowNodeUtilization Pod Pod Pod Pod Pod Pod thresholds: “pods": 2 targetThresholds: “pods”: 2 Pod Pod Pod targetThresholds: “pods”: 2 Pod ਺ 2 Λ௒͑ͨΒ
 ௥͍ग़͠ର৅
28. LowNodeUtilization Pod Pod Pod Pod Pod Pod thresholds: “pods": 2 targetThresholds: “pods”: 2 Pod thresholds: “pods": 2 Pod ਺ 2 ະຬͳΒ
 ଞͷ Node ͔Β
 Pod ΛҠಈͤͯ͞΋͍͍
29. LowNodeUtilization Pod Pod Pod Pod Pod thresholds: “pods": 2 targetThresholds: “pods”: 2 Pod Pod Run Descheduler
30. RemovePodsViolatingInterPodAntiAffinity • Inter-Pod Anti-Affinity ʹ
 ҧ൓͍ͯ͠Δ Pod ͕࡟আ͞ΕΔ • Inter-Pod Anti-Affinity • ಛఆͷϥϕϧΛ࣋ͬͨ Pod ͸ಉ͡ Node ʹ
 εέδϡʔϦϯά͠ͳ͍Α͏ʹ͢Δ΍ͭ
31. Pod C RemovePodsViolatingInterPodAntiAffinity Pod B Pod A Node
32. Pod C RemovePodsViolatingInterPodAntiAffinity Pod B Pod A Node Pod C Pod B Pod A Pod ͕ Node Ͱ
 ಈ͍͍ͯΔঢ়ଶͰ Pod B ͱ Pod C ʹ
 Pod A ͱಉ͡ϊʔυͰͷ
 ࣮ߦΛېࢭ͢Δ 
 Anti-Affinity rule Λ
 ௥Ճ͢Δ
33. Pod C RemovePodsViolatingInterPodAntiAffinity Pod B Pod A Node Anti-Affinity ͸
 εέδϡʔϧ͞ΕΔ͔࣌͠
 ݟͯ͘Εͳ͍ͷͰ
 Pod ͸Ҡಈͯ͘͠Εͳ͍
34. Pod C RemovePodsViolatingInterPodAntiAffinity Pod B Pod A Pod ͕
 ࠶εέδϡʔϦϯά͞ΕΔ Pod A Run Descheduler
35. RemovePodsViolatingNodeAffinity • Node Affinity ʹҧ൓͍ͯ͠Δ Pod ͕࡟আ͞ΕΔ • Node Affinity • Pod Λಛఆͷ Node ʹ
 εέδϡʔϦϯά͢ΔΑ͏ʹ͢Δ΍ͭ
36. Pod C Pod B Pod A Node RemovePodsViolatingNodeAffinity node: gopher-a node: gopher-b
37. Pod C Pod B Pod A Node RemovePodsViolatingNodeAffinity node: gopherA node: gopherB Pod A node: gopher-a Pod C Pod B Pod A ͸ node: gopher-a ͷϥϕϧͷ Node ʹ
 εέδϡʔϧ͢Δ
 Node Affinity
38. Pod C Pod B Pod A Node RemovePodsViolatingNodeAffinity node: gopher-a node: gopher-b Pod C Pod B Pod A Node node: gopher-a node: gopher-b ϥϕϧͷ෇͚ସ͑Λߦ͏
39. RemovePodsViolatingNodeAffinity Pod C Pod B Pod A Node node: gopher-a node: gopher-b Node Affinity ͸
 εέδϡʔϧ͞ΕΔ͔࣌͠
 ݟͯ͘Εͳ͍ͷͰ
 Pod ͸Ҡಈͯ͘͠Εͳ͍
40. RemovePodsViolatingNodeAffinity Pod C Pod B Pod A node: gopher-a node: gopher-b Pod A Run Descheduler Pod ͕
 ࠶εέδϡʔϦϯά͞ΕΔ
41. Pod ͷཱͪୀ͖ • ҎԼͷϧʔϧͰߦΘΕΔ • Critical Pods ͸ର৅֎ • Replica Set / Replication Controller / Deployment / Job
 ʹඥ͍͍ͮͯͳ͍ Pod ͸ର৅֎ • DaemonSet ͷ Pod ͸ର৅֎ • ϩʔΧϧετϨʔδΛ࣋ͭ Pod ͸ର৅֎ • QoS classes ͕ BestEffort ͷ Pod ͸ Guaranteed/ Burstable
 ΑΓ΋༏ઌͯ͠࡟আ͞ΕΔ
42. ͓͠·͍ Gopher ͘Μ͸͔͜͜Β: https://gopherize.me/