Kubernetes Frankfurt

What is this Docker thing?

• Acompany?

• Aformat?

• AnAPI?

Basic Docker components

3

Kube what?

4

Kubernetes

Greekfor“Helmsman”;alsotherootofthewords“governor”and “cybernetic”

• Runsandmanagescontainers• InspiredandinformedbyGoogle’sexperiencesand

internalsystems• Supportsmultiplecloudandbare-metal

environments• Supportsmultiplecontainerruntimes• 100%Opensource,writteninGo

Manageapplications,notmachines

Everything atGooglerunsincontainers:

• Gmail,WebSearch,Maps,...• MapReduce,batch,...• GFS,Colossus,...• EvenGoogle’sCloudPlatform: VMsrunincontainers!

Googlelaunchover2billioncontainersperweek

Start with a Cluster

• Laptop tohigh-availabilitymulti-nodecluster• Hosted orselfmanaged• On-Premise orCloud• BareMetal orVirtualMachines• MostOSes(inc. RedHat Atomic,Fedora,CentOS)• OrjustabunchofRaspberryPis• Manyoptions,SeeMatrixfordetails

Kubernetes Cluster Matrix: http://bit.ly/1MmhpMW

etcd

scheduler

controller-manager

apiserver

kubelet docker kube-proxy iptables

1. UsersendsPodrequesttoAPIserver

2. APIserversavespodinfotoetcd(unscheduled)

3. Schedulerfindsunscheduledpodandschedulesittonode.

4. Kubelet seespodscheduledtoitandtellsdocker torunthecontainer.

5. Dockerrunsthecontainer.

1

2

5

3

4

Kubelet Kubelet Kubelet

Kubernetes Master

Scheduler

API Server

Start with a Cluster

Theatomofschedulingforcontainers

Representsanapplicationspecificlogicalhost

Hostscontainers andvolumes

Eachhasitsownroutable(noNAT)IPaddress

Ephemeral• Podsarefunctionallyidenticalandtherefore

ephemeralandreplaceablePod

WebServer

Volume

Consumers

A pod of whales containers

Pods

Pod

GitSynchronizer

Node.jsAppContainer

Volume

ConsumersgitRepoCanbeusedtogroupmultiplecontainers&sharedvolumes

Containerswithinapodare tightly coupled

Sharednamespaces• ContainersinapodshareIP,portandIPC

namespaces• Containersinapodtalktoeachotherthrough

localhost

Pod Networking (across nodes)PodshaveIPswhichareroutable

PodscanreacheachotherwithoutNAT

Evenacrossnodes

NoBrokeringofPortNumbers

Thesearefundamentalrequirements

Manysolutions

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

Client

Pod

Container

Pod

Container

Pod

ContainerContainer

Alogicalgroupingofpodsthatperformthesamefunction• groupedbylabelselector

Loadbalancesincomingrequestsacrossconstituentpods

Choiceofpodisrandombutsupportssessionaffinity(ClientIP)

Getsastable virtualIPandport• alsoaDNSnametype =FE

Services

Service

Labelselector:type=FE

VIP

type=FE type=FE type=FE

Pod Pod

frontend

Pod

frontend

Pod Pod

type=FE

version=v2

type=FE version=v2

● Metadatawithsemanticmeaning

● Membershipidentifier

● TheonlyGroupingMechanism

Behavior Benefits➔ Allowforintentofmanyusers(e.g.dashboards)

➔ Buildhigherlevelsystems…

➔ QueryablebySelectors

Labels

Dashboard

selector:type=FE

Dashboard

selector:version=v2

ReplicationController Pod Pod

frontend

Pod

frontend

Pod Pod

ReplicationController

#pods=1version=v2

show:version=v2

version=v1 version=v1 version=v2

ReplicationController

#pods=2version=v1

show:version=v2Behavior Benefits

● KeepsPodsrunning

● GivesdirectcontrolofPods

● GroupedbyLabelSelector

➔ RecreatesPods,maintainsdesiredstate

➔ Fine-grainedcontrolforscaling

➔ Standardgroupingsemantics

Replication Controllers

Replication ControllersReplicationController

ReplicationController- Name=“backend”- Selector={“name”:“backend”}- Template={...}- NumReplicas=4

APIServer

3

Start1more

OK 4

Howmany?

Howmany?

Canonicalexampleofcontrolloops

Haveonejob:ensureNcopiesofapod• iftoofew,startnewones• iftoomany,killsome• group==selector

Replicatedpodsarefungible• Noimpliedorderoridentity

Pod Pod

frontend

Pod

frontend

Pod Pod

type=FE

version=v2

type=FE version=v2

● Metadatawithsemanticmeaning

● Membershipidentifier

● TheonlyGroupingMechanism

Behavior Benefits➔ Allowforintentofmanyusers(e.g.dashboards)

➔ Buildhigherlevelsystems…

➔ QueryablebySelectors

Labels

Dashboard

selector:type=FE

Dashboard

selector:version=v2

Deployment

RS

RS

Pod Pod Pod

env: test env: test env: test

Pod

env: testversion: v2 version: v2 version: v2 version: v2

Reliablemechanismforcreating,updatingandmanagingPods

Deploymentmanagesreplicachanges,includingrollingupdatesandscaling

EditDeploymentconfigurationsinplacewithkubectledit orkubectlapply

Managedrolloutsandrollbacks

Status:BETAinKubernetesv1.2

Deployments:UpdatesasaService

...

Pod Pod

frontend

Pod

frontend

Pod Pod

env=qa env=test

● env= prod

● tier!= backend

● env= prod,tier!=backend

Expressions● envin (test,qa)

● releasenotin (stable,beta)

● tier

● !tier

Generalized Labels (1.2)

env=prod

Pod

env=prod

Dashboard

selector:env=notin(prod)

ReplicationController Pod Pod

frontend

Pod

frontend

Pod Pod

app=demo app=demo app=demo

ReplicaSet

#pods=3app=democolorin(blue,grey)show:version=v2

SimilartoReplicationControllerbutsupportsgeneralizedSelectors

ReplicaSets(1.2)

selector:matchLabels:app:demomatchExpressions:- {key:color,operator:In,values:[blue,grey]}

color=blue color=blue color=grey

Rolling Update

kubectlrolling-update

API


Createfrontend-rc-v2



Scalefrontend-rc-v2upto1




Scalefrontend-rc-v1downto1

















Deletefrontend-rc-v1 Pod Pod

frontend

Pod

version=v1version=v2version=v1

RCversion= v1type= BE#pods=2

show:version=v2

type=BE type=BE


show:version=v2

Pod

version=v2

type=BE

kubectl rolling-updateisimperative,client-side


show:version=v2


show:version=v2


show:version=v2


show:version=v2


show:version=v2

be-svc

Rollout

API

DeploymentDeployment

Createfrontend-1234567

Deployment


Scalefrontend-1234567upto1

Deployment



Scalefrontend-7654321downto0

Pod Pod

frontend

Pod

version=v1

ReplicaSet

frontend-1234567version= v2type= BE#pods=0

show:version=v2

ReplicaSet


version:v2

ReplicaSet

frontend-7654321version:v1type:BE#pods=0

version:v1

ReplicaSet


show:version=v2

ReplicaSet

frontend-1234567version:v2type:BE#pods=2

type=BE type=BE

Pod

version:v2

type=BE

Servicebe-svc

Deployment



Scalefrontend-7654321downto0


kubectleditdeployment...

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@Loodse

github.com/loodse/

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Kubernetes Frankfurt