Kubernetes Concepts and Terms explained at a very high level

1. Kubernetes in
20 minutes
HDE Monthly Technical Session
July 22, 2016
Daisuke Maki @lestrrat

3. Netscape Navigator

4. Netscape Navigator

5. Kubernetes

6. κυβερνήτης

7. k8s

8. “Something to do with
containers…?

9. •You know about containers
•You know about orchestration
•You know about the painful art of
deploying stuff
Assumptions

10. Docker

11. “Random containers doing their own sh*t”

12. Compose

13. “Foreman on Acid”

14. Swarm

15. “Clustering and Discovery”
(hey, we’re getting somewhere!)

16. =

17. “Batteries Included”

18. K8s on GCP
GKE GCE Networking
…and others

19. Basic Concepts

20. Node

21. Hosts running
k8s daemons

22. Node
kubelet
Node
kubelet
Node
kubelet
Master
Scheduler
etc..
API

23. Pod

24. Basic unit of
deployment in k8s

25. Group of Containers

26. Container configurations

27. Shared storage

28. Pod
container

29. Pod
container
container

30. Pod
container
container
container

31. Pod
container
container
container
nginx
app
redis/cache
e.g.

32. Scheduled together
(“co-scheduled”)

33. Guaranteed to be
on the same node
(“co-located”)

34. Node NodeNode

35. Node NodeNode
Depends on each node’s resource availability
and each pod’s resource requirements

36. Node Node
container
container
container

37. Node Node
container
container
container
This will NEVER happen

38. Miscellaneous
• Each pod has its own IP address
• Pods are expected to be stateless

39. Replica Set

40. Keeps track of
Pod replicas

41. Replica Set
replicas: 3
template:

42. Replica Set
replicas: 3
template:
A

43. Replica Set
replicas: 3
template:
A B

44. Replica Set
replicas: 3
template:
CA B

45. Replica Set
replicas: 3
template:
CA B

46. Replica Set
replicas: 3
template:
A B

47. Replica Set
replicas: 3
template:
A B D

48. Deployment

49. Manages Replica Set
state transitions

50. Deployment
replicas: 3
template:

51. Deployment
replicas: 3
template:
Replica Set A
replicas: 3
template:

52. Deployment
replicas: 3
template:
Replica Set A
replicas: 3
template:
Change some settings,
please!

53. Deployment
replicas: 3
template:
Replica Set A
replicas: 3
template:
2
Change some settings,
please!

54. Deployment
replicas: 3
template:
Replica Set A
replicas: 3
template:
Replica Set B
replicas: 2
template:
2
Change some settings,
please!

55. Deployment
replicas: 3
template:
Replica Set A
replicas: 3
template:
Replica Set B
replicas: 2
template:
2
Change some settings,
please!

56. Deployment
replicas: 3
template:
Replica Set B
replicas: 2
template:
2
Change some settings,
please!

57. Keeps track of
state change history

58. Deployment
replicas: 3
template:

59. Deployment
replicas: 3
template:
A
replicas: 3
template:

60. Deployment
replicas: 3
template:
A
replicas: 3
template:
Change some settings,
please!

61. Deployment
replicas: 3
template:
A
replicas: 3
template:
2
Change some settings,
please!

62. Deployment
replicas: 3
template:
A
replicas: 3
template:
B
replicas: 2
template:
2
Change some settings,
please!

63. Deployment
replicas: 3
template:
A
replicas: 3
template:
B
replicas: 2
template:
2
Change some settings,
please!

64. Deployment
replicas: 3
template:
B
replicas: 2
template:
2
Change some settings,
please!

65. Deployment
replicas: 3
template:
B
replicas: 2
template:
2
Oh wait, I actually
didn’t want to do that…

66. Deployment
replicas: 3
template:
B
replicas: 2
template:
2
Oh wait, I actually
didn’t want to do that…
3

67. Deployment
replicas: 3
template:
B
replicas: 2
template:
2
Oh wait, I actually
didn’t want to do that…
rollback
3

68. Deployment
replicas: 3
template:
B
replicas: 2
template:
2
Oh wait, I actually
didn’t want to do that…
rollback
A
replicas: 3
template:
3

69. Deployment
replicas: 3
template:
B
replicas: 2
template:
2
Oh wait, I actually
didn’t want to do that…
rollback
A
replicas: 3
template:
3

70. Deployment
replicas: 3
template:
2
Oh wait, I actually
didn’t want to do that…
A
replicas: 3
template:
3

71. Services

72. Logical set of Pods
(and ways to access them)

73. Pod 10.0.96.2
Pod 10.0.96.3
Pod 10.0.96.3
Raw Pod Access

74. Pod 10.0.96.2
Pod 10.0.96.3
Pod 10.0.96.3
Raw Pod Access

75. Pod 10.0.96.2
Pod 10.0.96.3
Pod 10.0.96.3
Raw Pod Access

76. Pod 10.0.96.2
Pod 10.0.96.3
Raw Pod Access

77. Pod 10.0.96.2
Pod 10.0.96.3
Raw Pod Access

78. Pod 10.0.96.3
role=web
Access Via Service
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

79. Pod 10.0.96.3
role=web
Access Via Service
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

80. Pod 10.0.96.3
role=web
Access Via Service
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

81. Pod 10.0.96.3
role=web
Access Via Service
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

82. Access Via Service
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

83. Access Via Service
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

84. Access Via Service
Pod 10.0.96.6
role=web
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

85. Access Via Service
Pod 10.0.96.6
role=web
Pod 10.0.96.4
role=web
Service
match role=web
Pod 10.0.96.2
role=web
Pod 10.0.96.5
role=db

86. Secrets

87. Store pieces of
data in k8s

88. e.g. Identity Information

89. (securely)

90. (…in the future)

91. Secret
key1 → base64 value
key3 → base64 value
key2 → base64 value

92. Pod
container
volumes
container:
volumeMounts:
- name: certificates
mountPath: /etc/ssl/certs
volumes:
- name: certificates
secret:
secretName: ca-certificates

93. ConfigMaps

94. Same as Secrets
(Unprotected)

95. Ingress

96. Services are for within
the cluster only

97. (New since 1.2)
Inbound connections to
internal cluster services

98. Please checkout my presentation
https://docs.google.com/presentation/d/
11ZN6qgiuZZfVyhBK2hjp1vhp_5N0DOGnAmhPreS3L5A/pub?
start=false&loop=false&delayms=3000

99. DaemonSets

100. Ensure nodes run a copy of a Pod
Node
prometheus-exporter prometheus-exporter prometheus-exporter
Node Node

101. PetSets

102. snip.

103. Questions?

104. Appendix: ECS vs GKE
https://railsadventures.wordpress.com/2015/12/06/why-we-
chose-kubernetes-over-ecs/

105. If you want to play with k8s, I’m doing this entirely on GCP/GKE…
Come Join https://slack-invite-dot-builderscon-1248.appspot.com/