Helm

Besmart.Thinkopensource.

WhatisHelm?HelmisatoolformanagingKubernetescharts.

Chartsarepackagesofpre-configuredresources.

Thinkofitlikeapt/yum/homebrewforKubernetes.

WhyHelm?

De-factostandardfortemplatingk8sconfigsOfficialKubernetesprojectmaintainedbyCNCFRepeatableapplicationinstallationsPainlessupdatesShipswithreadytousechartsmadebythecommunitybestpracticesarebakedintoofficalchartsApplicationLifecycle/Upgrades

What'swrongwithkubectl?

ResourcesneedtobemutatedafteradeployYoucan kubectleditBut,needtoimplementyourownupdatingandrollbackordependonvendorspecifictoolingforlifecyclemanagement

Helmhelpswithlifecyclemanagmentwhileallowingyoutodefineyourinfrastructureascode

HelmBasics

Architecture

helmclientonyourlocalmachine(likekubectl)tillerserver-sidecomponent(deployedonKubernetes)

Quickstart#deploytillertokube-systemnamespacehelminit#Deployapostgresqlinstancehelminstallstable/postgresql

Inspectinghelmmanagedresources#Showdeployshelmlist#Getinformationonareleasehelmstatusmy-release

HelmreleasesDifferentiatemultipledeploysofachartwithreleases.

Possiblevaluescouldbe.

production , stage , integration-production

-postgresql

Thisdependsonyourorganizationsstructureandwhatyouusetheclusterfor.

Whatdidwejustdeploy?

Deploymentbasedon postgres imageNetworkPolicyallowingaccess.PersistentVolumeClaimforstoringdataSecretcontainingautogeneratedpostgres-password

Servicetoexposedatabaseincluster

Rollback#simulaterollbackhelmrollback--dry-runmy-releaseold-version#actualrollbackhelmrollbackmy-releaseold-version

Writinghelmcharts

helmcreatemy-app

my-app/├──charts├──Chart.yaml├──templates│├──deployment.yaml│├──_helpers.tpl│├──ingress.yaml│├──NOTES.txt│└──service.yaml└──values.yaml

TemplatingTheHelmtemplatelanguageisimplementedinthestronglytypedGolanguage.

EachHelmchartcontainsatemplatesdirectorythatcontainsrelevanttemplates.

NamingTemplates

Use .yaml or .tpl suffixforfilesDasherizefilenamesReflectresourcekindinnames

Good Badfoo-pod.yaml foo-pod.yml

my-example-podtemplates.yaml MyExamplePodTemplates.yaml

my-example-svc.yaml my-example.yaml

Built-inObjects

Everythingbelow ReleaseChart variablewithinfosfrom Chart.yamlValues withdatafrom values.yaml ,thecliandothersources

AcompletelistisintheHelmdocs

https://docs.helm.sh/chart_template_guide/#built-in-objects

#Currentrelease{{.Release.Revision}}#Chartinfos{{.Chart.version}}

ValuesThebuilt-inobjectValuesisemptybydefault.Chartsanduserscanaddtoitthrough values.yaml ,user-suppliedfilesandontheCLI.

Let'sseehowvaluesgetpopulatedwithasimpletemplate.

echo'{{.Values.hello.world}}'>templates/hello.tpl

Defaultvaluesareinthecharts values.yaml#values.yamlhello:world:Hello!

helmtemplate.-xtemplates/hello.yaml

---#Source:my-chart/templates/hello.yamlHello!

OverridingvaluesontheCLIhelmtemplate.--executetemplates/hello.yaml\--set'hello.world=Hallo!'

---#Source:my-chart/templates/hello.yamlHallo!

FlowControl

if / else forcreatingconditionalblockswith tospecifyascoperange ,whichprovidesa"foreach"-styleloop

if / else{{-if.Values.ingress.enabled-}}apiVersion:extensions/v1beta1kind:Ingress#...{{-end-}}

range

#...spec:rules:{{-range.Values.server.ingress.hosts}}-host:{{.}}{{-end-}}#...

DebuggingTemplates#verifythatchartfollowsbestpracticeshelmlint#letserverrendertemplatesandreturnresultingmanifesthelminstall--dry-run--debug.

HelmSubCharts

Composingsystemswithsubcharts

Chartscandependonothercharts.Dependenciesaredescribedin requirements.yaml .helmdepbuild creates requirements.lock .

#downloaddependencieshelmdepbuildstable/redmine

#installredminewithpostgresqlhelminstallstable/redmine\--setdatabaseType.mariadb=false,databaseType.postgresql=true

SubchartsandValues

subchartscannotdependontheirparentchartsvalues.parentchartscanoverridevaluesforsubcharts.globalvaluescanbeaccessedfromanychart.

#overridepostgresqlvaluespostgresql:postgresPassword:muchsecretverysecure

#definesomeglobalvariablesglobal:myVariable:myValue

Pleaseplanaheadwhenusingglobalsordon'tusethematall.Officialchartsrarelyusethem.

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