ReplicaSet101

Demystifying

theNuts&Boltsof

Kubernetes

Architecture

ReplicaSet101

2

WhoAmI?

• PrincipalSystemsDevelopmentEngineeratDellEMC

• WorkedwithVMware&CGI

• DockerCaptain|DockerCommunityLeader

• CollabnixSlack–1800+Members

• DockerLabs–500+tutorials

http://www.collabnix.com

Howcanyouensurethatthereare3Podsinstanceswhich

arealwaysavailableandrunningatonepointintime?

WhatisReplicaSetallabout?

MaintainastablesetofreplicaPodsrunningatanygiventime

• EnsuresthataspecifiednumberofPodsarerunningatanytime



a.IfthereareaccessPods,theygetkilledandviceversa

b.NewPodsarelaunchedwhentheygetfailed,getdeletedandterminated

-ReplicaSet&Podsareassociatedwith“labels”

ReplicationControllerVsReplicaSet

• ReplicaSetisthenextgenerationofReplicationController

• Bothservethesamepurpose

ReplicaSetReplicationController

Set-basedSelectors

Equality-basedSelectors

Labels&Selectors

WhenPodsarescaled,howarethesePodsManagedatsuchlargescale?

Pods

Controllers&Services

Labels

Selectors

#Pod-Spec

apiVersion:v1

kind:pod

metadata:

name:nginx-Pod

labels:

app:guestbook

tier:frontend

env:dev

spec:

replicas:5..

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Equality-basedSelectorsSet-basedSelectors

Operators:

=and==

Examples:

environment=production

tier!=frontend

Commandline:

$kubectlgetpods-lenvironment=production

InManifest:

..

selector:

environment:production

tier:frontend

..

Operators:

innotinexists

Examples:

environmentin(production,qa)

tiernotin(frontend,backend)

Commandline:

$kubectlgetpods-l`enviornmentin(production)

InManifest:

..

selector:

matchExpressions:

-{key:environment,operator:in,values:[prod,qa]}

-{key:tier,operator:Notin,values:[frontend,backend]}

..

Supports:Services,ReplicationController

Supports:Job,Deployment,ReplicaSet,DaemonSet

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ReplicaSetExamples:

§ Manifestfile

§ DeployappusingRS

§ DisplayandvalidateRS

§ Test–NodeFails

§ Test–ScaleUp

§ Test–ScaleDown

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ReplicaSetManifestFile

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CreatingNginx-rsPods

$kubectlcreate–fnginx-rs.yaml

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CheckingthestateofReplicaSet

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ScalingtheNginxService

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Demo

• CreatingYourFirstReplicaSet-4PodsservingNginx

• RemovingaPodfromReplicaSet

• Scaling&AutoscalingaReplicaSet

• BestPractices

• DeletingReplicaSets