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

Netscape Navigator

Netscape Navigator

Kubernetes

κυβερνήτης

k8s

“Something to do with
containers…?

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

Docker

“Random containers doing their own sh*t”

Compose

“Foreman on Acid”

Swarm

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

=

“Batteries Included”

K8s on GCP
GKE GCE Networking
…and others

Basic Concepts

Node

Hosts running
k8s daemons

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

Pod

Basic unit of
deployment in k8s

Group of Containers

Container configurations

Shared storage

Pod
container

Pod
container
container

Pod
container
container
container

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

Scheduled together
(“co-scheduled”)

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

Node NodeNode

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

Node Node
container
container
container

Node Node
container
container
container
This will NEVER happen

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

Replica Set

Keeps track of
Pod replicas

Replica Set
replicas: 3
template:

Replica Set
replicas: 3
template:
A

Replica Set
replicas: 3
template:
A B

Replica Set
replicas: 3
template:
CA B

Replica Set
replicas: 3
template:
CA B

Replica Set
replicas: 3
template:
A B

Replica Set
replicas: 3
template:
A B D

Deployment

Manages Replica Set
state transitions

Deployment
replicas: 3
template:

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

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

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

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

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

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

Keeps track of
state change history

Deployment
replicas: 3
template:

Deployment
replicas: 3
template:
A
replicas: 3
template:

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

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

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

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

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

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

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

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

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

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

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

Services

Logical set of Pods
(and ways to access them)

Pod 10.0.96.2
Pod 10.0.96.3
Pod 10.0.96.3
Raw Pod Access

Pod 10.0.96.2
Pod 10.0.96.3
Pod 10.0.96.3
Raw Pod Access

Pod 10.0.96.2
Pod 10.0.96.3
Pod 10.0.96.3
Raw Pod Access

Pod 10.0.96.2
Pod 10.0.96.3
Raw Pod Access

Pod 10.0.96.2
Pod 10.0.96.3
Raw Pod Access

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

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

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

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

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

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

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

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

Secrets

Store pieces of
data in k8s

e.g. Identity Information

(securely)

(…in the future)

Secret
key1 → base64 value
key3 → base64 value
key2 → base64 value

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

ConfigMaps

Same as Secrets
(Unprotected)

Ingress

Services are for within
the cluster only

(New since 1.2)
Inbound connections to
internal cluster services

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

DaemonSets

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

PetSets

snip.

Questions?

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

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/