This document provides an overview of Kubernetes, an open-source system for automating deployment, scaling, and management of containerized applications. It describes basic Kubernetes components like pods, replication controllers, services, deployments, and replica sets. It explains how Kubernetes is used to group and schedule containers, maintain desired pod counts, update applications seamlessly with rolling updates, and more. The document also notes Kubernetes was inspired by Google's internal container systems and can manage applications across cloud and bare-metal environments.

1. Kubernetes Overview
Sebastian Scheele

2. What is this Docker thing?
• A company?
• A format?
• An API?

3. Basic Docker components
3

4. Kube what?
4

5. Kubernetes
Greek for “Helmsman”; also the root of the words
“governor” and “cybernetic”
• Runs and manages containers
• Inspired and informed by Google’s experiences and
internal systems
• Supports multiple cloud and bare-metal
environments
• Supports multiple container runtimes
• 100% Open source, written in Go
Manage applications, not machines

6. Everything at Google runs
in containers:
• Gmail, Web Search, Maps, ...
• MapReduce, batch, ...
• GFS, Colossus, ...
• Even Google’s Cloud Platform: VMs
run in containers!
Google launch over 2 billion
containers per week

7. Start with a Cluster
• Laptop to high-availability multi-node cluster
• Hosted or self managed
• On-Premise or Cloud
• Bare Metal or Virtual Machines
• Most OSes (inc. RedHat Atomic, Fedora, CentOS)
• Or just a bunch of Raspberry Pis
• Many options, See Matrix for details
Kubernetes Cluster Matrix: http://bit.ly/1MmhpMW

8. etcd
scheduler
controller-
manager
apiserver
kubelet docker kube-proxy iptables
1. User sends Pod request to API
server
2. API server saves pod info to etcd
(unscheduled)
3. Scheduler finds unscheduled pod
and schedules it to node.
4. Kubelet sees pod scheduled to it
and tells docker to run the
container.
5. Docker runs the container.
1
2
5
3
4

9. Kubelet Kubelet Kubelet
Kubernetes Master
Scheduler
API Server
Start with a Cluster

10. Picture of Whales

11. The atom of scheduling for containers
Represents an application specific logical
host
Hosts containers and volumes
Each has its own routable (no NAT) IP
address
Ephemeral
• Pods are functionally identical and therefore
ephemeral and replaceable
Pod
Web Server
Volume
Consumers
A pod of whales containers

12. Pods
Pod
Git
Synchronizer
Node.js App
Container
Volume
Consumersgit Repo
Can be used to group multiple containers &
shared volumes
Containers within a pod are tightly
coupled
Shared namespaces
• Containers in a pod share IP, port and IPC
namespaces
• Containers in a pod talk to each other through
localhost

13. Pod Networking (across nodes)
Pods have IPs which are routable
Pods can reach each other without NAT
• Even across nodes
No Brokering of Port Numbers
These are fundamental requirements
Many solutions
• GCE Advanced Routes, AWS Flannel, Weave,
OpenVSwitch, Cloud Provider
10.1.2.0/24
10.1.1.0/24
10.1.1.211 10.1.1.2
10.1.2.106
10.1.3.0/24
10.1.3.4510.1.3.17
10.1.3.0/24

14. Client
Pod
Container
Pod
Container
Pod
ContainerContainer
A logical grouping of pods that perform the same
function
• grouped by label selector
Load balances incoming requests across
constituent pods
Choice of pod is random but supports session
affinity (ClientIP)
Gets a stable virtual IP and port
• also a DNS nametype = FE
Services
Service
Label selector:
type = FE
VIP
type = FE type = FE type = FE

15. Pod
Pod
frontend
Pod
frontend
Pod Pod
type = FE
version = v2
type = FE version = v2
● Metadata with semantic meaning
● Membership identifier
● The only Grouping Mechanism
Behavior Benefits
➔ Allow for intent of many users (e.g. dashboards)
➔ Build higher level systems …
➔ Queryable by Selectors
Labels
Dashboard
selector:
type = FE
Dashboard
selector:
version = v2

16. Replication
Controller
Pod
Pod
frontend
Pod
frontend
Pod Pod
Replication
Controller
#pods = 1
version = v2
show: version = v2
version= v1 version = v1 version = v2
Replication
Controller
#pods = 2
version = v1
show: version = v2
Behavior Benefits
● Keeps Pods running
● Gives direct control of Pods
● Grouped by Label Selector
➔ Recreates Pods, maintains desired state
➔ Fine-grained control for scaling
➔ Standard grouping semantics
Replication Controllers

17. Replication Controllers
Replication Controller
- Name = “backend”
- Selector = {“name”: “backend”}
- Template = { ... }
- NumReplicas = 4
API Server
3
Start 1
more
OK 4
How
many?
How
many?
Canonical example of control loops
Have one job: ensure N copies of a
pod
• if too few, start new ones
• if too many, kill some
• group == selector
Replicated pods are fungible
• No implied order or identity

18. Pod
Pod
frontend
Pod
frontend
Pod Pod
type = FE
version = v2
type = FE version = v2
● Metadata with semantic meaning
● Membership identifier
● The only Grouping Mechanism
Behavior Benefits
➔ Allow for intent of many users (e.g. dashboards)
➔ Build higher level systems …
➔ Queryable by Selectors
Labels
Dashboard
selector:
type = FE
Dashboard
selector:
version = v2

19. Rolling Update
kubectl rolling-update
API
kubectl rolling-update
Create frontend-rc-v2
kubectl rolling-update
Create frontend-rc-v2
Scale frontend-rc-v2 up to 1
kubectl rolling-update
Create frontend-rc-v2
Scale frontend-rc-v2 up to 1
Scale frontend-rc-v1 down to 1
kubectl rolling-update
Create frontend-rc-v2
Scale frontend-rc-v2 up to 1
Scale frontend-rc-v1 down to 1
Scale frontend-rc-v2 up to 2
kubectl rolling-update
Create frontend-rc-v2
Scale frontend-rc-v2 up to 1
Scale frontend-rc-v1 down to 1
Scale frontend-rc-v2 up to 2
Scale frontend-rc-v1 down to 0
kubectl rolling-update
Scale frontend-rc-v2 up to 1
Scale frontend-rc-v1 down to 1
Scale frontend-rc-v2 up to 2
Scale frontend-rc-v1 down to 0
Delete frontend-rc-v1 Pod Pod
frontend
Pod
version = v1version = v2version= v1
RC
version = v1
type = BE
#pods = 2
show: version = v2
type = BE type = BE
RC
version = v2
type = BE
#pods = 0
show: version = v2
Pod
version = v2
type = BE
kubectl rolling-update is imperative, client-side
RC
version = v1
type = BE
#pods = 2
show: version = v2
RC
version = v1
type = BE
#pods = 1
show: version = v2
RC
version = v1
type = BE
#pods = 0
show: version = v2
RC
version = v2
type = BE
#pods = 1
show: version = v2
RC
version = v2
type = BE
#pods = 2
show: version = v2
be-svc

20. Deployment
RS
RS
Pod Pod Pod
env: test env: test env: test
Pod
env: test
version: v2 version: v2 version: v2 version: v2

21. Reliable mechanism for creating, updating and
managing Pods
Deployment manages replica changes,
including rolling updates and scaling
Edit Deployment configurations in place with
kubectl edit or kubectl apply
Managed rollouts and rollbacks
Status: BETA in Kubernetes v1.2
Deployments: Updates as a Service
...

22. Pod
Pod
frontend
Pod
frontend
Pod Pod
env = qa env = test
● env = prod
● tier != backend
● env = prod, tier !=backend
Expressions
● env in (test,qa)
● release notin (stable,beta)
● tier
● !tier
Generalized Labels (1.2)
env = prod
Pod
env = prod
Dashboard
selector:
env = notin(prod)

23. Replication
Controller Pod
Pod
frontend
Pod
frontend
Pod Pod
app = demo app = demo app = demo
ReplicaSet
#pods = 3
app = demo
color in (blue,grey)
show: version = v2
Similar to ReplicationController but supports generalized Selectors
ReplicaSets (1.2)
selector:
matchLabels:
app: demo
matchExpressions:
- {key: color, operator: In, values: [blue,grey]}
color = blue color = blue color = grey

24. Rollout
API
DeploymentDeployment
Create frontend-1234567
Deployment
Create frontend-1234567
Scale frontend-1234567 up to 1
Deployment
Create frontend-1234567
Scale frontend-1234567 up to 1
Scale frontend-7654321 down to 0
Pod Pod
frontend
Pod
version = v1
ReplicaSet
frontend-1234567
version = v2
type = BE
#pods = 0
show: version = v2
ReplicaSet
frontend-7654321
version = v1
type = BE
#pods = 2
version: v2
ReplicaSet
frontend-7654321
version: v1
type: BE
#pods = 0
version: v1
ReplicaSet
frontend-1234567
version = v2
type = BE
#pods = 1
show: version = v2
ReplicaSet
frontend-1234567
version: v2
type: BE
#pods = 2
type = BE type = BE
Pod
version: v2
type = BE
Servic
e
be-svc
Deployment
Create frontend-1234567
Scale frontend-1234567 up to 1
Scale frontend-7654321 down to 0
Scale frontend-1234567 up to 2
kubectl edit deployment ...

25. Thank you
www.loodse.com
@Loodse
github.com/loodse/