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Introduction to kustomize Kubernetes Meetup Tokyo #12, Jul 11, 2018

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@spesnova SRE at Mercari, Inc. / Kubernetes Tokyo Community Organizer

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Agenda

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1. Basics 2. Features 3. Keys

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Tested with kustomize v1.0.3

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Basics

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What is kustomize?

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kustomize is a command line tool

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kustomize is a CLI for managing k8s style object with declarative way

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Let’s learn a basic usage!

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Basics / Hello World

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• 3 environments (dev, stg, prod) • 1 deployment resource • different replicas by environments Example Requirements

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hello-world/ ├── base │ ├── deployment.yaml │ └── kustomization.yaml └── overlays ├── production │ ├── replica_count.yaml │ └── kustomization.yaml └── staging ├── replica_count.yaml └── kustomization.yaml File Structure

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hello-world/ ├── base │ ├── deployment.yaml │ └── kustomization.yaml └── overlays ├── production │ ├── replica_count.yaml │ └── kustomization.yaml └── staging ├── replica_count.yaml └── kustomization.yaml File Structure

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hello-world/ ├── base │ ├── deployment.yaml │ └── kustomization.yaml └── overlays ├── production │ ├── replica_count.yaml │ └── kustomization.yaml └── staging ├── replica_count.yaml └── kustomization.yaml File Structure

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hello-world/ ├── base │ ├── deployment.yaml │ └── kustomization.yaml └── overlays ├── production │ ├── replica_count.yaml │ └── kustomization.yaml └── staging ├── replica_count.yaml └── kustomization.yaml File Structure

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hello-world/ ├── base │ ├── deployment.yaml │ └── kustomization.yaml └── overlays ├── production │ ├── replica_count.yaml │ └── kustomization.yaml └── staging ├── replica_count.yaml └── kustomization.yaml Base

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# hello-world/base/deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: name: hello-world spec: replicas: 1 selector: matchLabels: app: hello-world template: .. Base

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# hello-world/base/kustomization.yaml resources: - deployment.yaml Base

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hello-world/ ├── base │ ├── deployment.yaml │ └── kustomization.yaml └── overlays ├── production │ ├── replica_count.yaml │ └── kustomization.yaml └── staging ├── replica_count.yaml └── kustomization.yaml Staging

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# hello-world/staging/replica_count.yaml apiVersion: apps/v1 kind: Deployment metadata: name: hello-world spec: replicas: 3 Staging

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# hello-world/staging/kustomization.yaml bases: - ../../base patches: - replica_count.yaml Staging

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$ kustomize build -h Print current configuration per contents of kustomization.yaml Usage: kustomize build [path] [flags] $ kustomize build

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$ kustomize build hello-world/overlays/staging/ Print staging configuration

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apiVersion: apps/v1 kind: Deployment metadata: name: hello-world spec: replicas: 3 selector: matchLabels: app: hello-world template: .. Print staging configuration

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template-free customization

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overlay customization

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base deployment (replicas 1)

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staging deployment (replicas: 3)

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overlayed staging deployment (replicas 3)

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hello-world/ ├── base │ ├── deployment.yaml │ └── kustomization.yaml └── overlays ├── production │ ├── replica_count.yaml │ └── kustomization.yaml └── staging ├── replica_count.yaml └── kustomization.yaml Production

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# hello-world/production/replica_count.yaml apiVersion: apps/v1 kind: Deployment metadata: name: hello-world spec: replicas: 7 Production

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# hello-world/production/kustomization.yaml bases: - ../../base patches: - replica_count.yaml Production

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$ kustomize build hello-world/overlays/production/ Print production configuration

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apiVersion: apps/v1 kind: Deployment metadata: name: hello-world spec: replicas: 7 selector: matchLabels: app: hello-world template: .. Print production configuration

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$ kustomize build [PATH] | kubectl apply -f - Apply printed configuration

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Basics / Motivation

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Declarative specification is the recommended way

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However…

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It’s difficult to use only current kubectl to follow declarative way…

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Then…

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• Helm • Ksonnet • Kapitan • Forge • Ktmpl • etc… Another Tools are required

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1. I have to learn new tools… 2. I have to learn new DSL… (complicated!) 3. I have to teach new concepts to teams… Drawbacks of those tools

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Features

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Features / Name Prefix

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# overlays/production/kustomization.yaml namePrefix: prod- bases: - ../../base patches: - replica_count.yaml Name Prefix

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$ kustomize build hello-world/overlays/production/ Name Prefix

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apiVersion: apps/v1 kind: Deployment metadata: name: prod-hello-world spec: replicas: 7 selector: matchLabels: app: hello-world template: .. Name Prefix

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Features / Common Labels

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# base/kustomization.yaml commonLabels: owner: spesnova resources: - deployment.yaml Common Labels

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$ kustomize build hello-world/overlays/production/ Common Labels

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apiVersion: apps/v1 kind: Deployment metadata: name: hello-world labels: owner: spesnova spec: replicas: 7 selector: matchLabels: app: hello-world template: .. Common Labels

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Features / Common Annotattion

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# base/kustomization.yaml commonAnnotations: description: This is Hello World App resources: - deployment.yaml Common Annotations

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$ kustomize build hello-world/overlays/production/ Common Annotations

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apiVersion: apps/v1 kind: Deployment metadata: name: hello-world annotations: description: This is Hello World App spec: replicas: 7 selector: matchLabels: app: hello-world template: … Common Annotations

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Features / ConfigMap Generator

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# base/kustomization.yaml resources: - deployment.yaml configMapGenerator: - name: hello-config files: - hello.config ConfigMap Generator

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# hello.config name=hello-world region=tokyo ConfigMap Generator

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$ kustomize build hello-world/overlays/production/ ConfigMap Generator

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apiVersion: v1 data: hello.config: | name=hello-world region=tokyo kind: ConfigMap metadata: creationTimestamp: null name: hello-config-4g5t58m8t5 --- apiVersion: apps/v1 kind: Deployment … ConfigMap Generator

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apiVersion: v1 data: hello.config: | name=hello-world region=tokyo kind: ConfigMap metadata: creationTimestamp: null name: hello-config-4g5t58m8t5 --- apiVersion: apps/v1 kind: Deployment … Hash suffix

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# hello.config name=hello-world region=london Hash suffix

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apiVersion: v1 data: hello.config: | name=hello-world region=tokyo kind: ConfigMap metadata: creationTimestamp: null name: hello-config-bdmmkghm2m --- apiVersion: apps/v1 kind: Deployment … Hash suffix

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Features / Secrets Generator (skip)

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Features / Diff

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$ kustomize diff hello-world/overlays/production/ $ kustomize diff

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@@ -3,7 +3,7 @@ metadata: name: hello-world spec: - replicas: 1 + replicas: 7 selector: matchLabels: app: hello-world $ kustomize diff

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Features / Substitute (skip)

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Workflows / Bespoke config

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Bespoke config

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Workflows / Off-the-shelf config

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Off-the-shelf config

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Keys

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Keys / Overlay vs Template

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1. Can only override parameterized config 2. DSL is too complicated for human 3. Most tools can not read DSL Drawbacks of Templating

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1. I’m using official Redis Helm chart 2. I want to add annotation 3. Annotations are not defined in the chart… 4. …Fork? Example

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With kustomize You can override any part of config with kustomize

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Keys / Single source of truth

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1. There is a config file “hello.config” 2. Copy contents of the file 3. Paste it into configMap 4. … I have 2 config sources… Before kustomize

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# base/kustomization.yaml resources: - deployment.yaml configMapGenerator: - name: hello-config files: - hello.config ConfigMap Generator

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# hello.config name=hello-world region=tokyo ConfigMap Generator

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$ kustomize build hello-world/overlays/production/ ConfigMap Generator

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apiVersion: v1 data: hello.config: | name=hello-world region=tokyo kind: ConfigMap metadata: creationTimestamp: null name: hello-config-4g5t58m8t5 --- apiVersion: apps/v1 kind: Deployment … ConfigMap Generator

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1. There is a config file “hello.config” 2. Run “kustomize build” 3. kustomize generates configMap 4. The config source is only “hello.config” After kustomize

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Keys / Rolling ConfigMap Update

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1. Update contents of existing configMap 2. Deployment itself is not changed… 3. Deployment still reads old configMap… Updating existing configMap

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apiVersion: v1 data: hello.config: | name=hello-world region=tokyo kind: ConfigMap metadata: creationTimestamp: null name: hello-config-4g5t58m8t5 --- apiVersion: apps/v1 kind: Deployment … Hash suffix

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1. Update contents of configMap 2. kustomize prints new configMap 3. Update configMap name in deployment 4. Deployment reads new configMap Rolling ConfigMap Update

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Keys / Teaching native k8s APIs

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kustomize exposes and teaches native k8s APIs, rather than hiding them. IUUQTHJUIVCDPNLVCFSOFUFTTJHTLVTUPNJ[FCMPCNBTUFSEPDTHMPTTBSZNE

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Same as kubernetes manifest Using Native Kubernetes API

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1. Lower learning cost 2. Deeper understanding about Kubernetes Using Native Kubernetes API

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Keys / Rollback

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$ git checkout XXXXXX $ kustomize build [PATH] | kubectl apply -f - Rollback

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kustomize rollback is very good for GitOps. However, I also like heroku style rollback such as “helm status”, “helm history”, “helm rollback”. Helm provides us logical group of k8s resources as “application”. kustomize doesn’t. Rollback

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Kubernetes Application proposal KEP Related issue https://github.com/kubernetes/community/pull/1629

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Keys / might be moved to kubectl

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Kustomize was initially developed as its own cli, however once it has matured, it should be published as a subcommand of kubectl or as a statically linked plugin. IUUQTHJUIVCDPNLVCFSOFUFTDPNNVOJUZCMPCNBTUFSLFQTTJHDMJLVTUPNJ[FNEJNQMFNFOUBUJPOEFUBJMTOPUFTDPOTUSBJOUTPQUJPOBM

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Keys / See design doc!

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https://github.com/kubernetes/community/blob/master/contributors/ design-proposals/architecture/declarative-application- management.md IUUQTHJUIVCDPNLVCFSOFUFTDPNNVOJUZCMPCNBTUFSLFQTTJHDMJLVTUPNJ[FNEJNQMFNFOUBUJPOEFUBJMTOPUFTDPOTUSBJOUTPQUJPOBM It’s awesome!

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It’s awesome! If kustomize looks easy to use for you, I think it comes from good design!

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Questions

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Can I delete labels with overlay? As far as I know, you can not for now

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End