Docker & Kubernetes for Developers · 강의

StatefulSets를 활용한 상태 저장 애플리케이션 관리

StatefulSets를 사용해 데이터베이스와 같은 상태 저장 애플리케이션을 배포하고 관리하며 안정적인 네트워크 ID와 영구 스토리지를 보장합니다.

StatefulSets를 활용한 상태 저장 애플리케이션 관리은(는) CoddyKit의 무료 Docker & Kubernetes for Developers 강의입니다. 이것은 4개 중 2번째 강의입니다. 아래에서 전체 강의를 무료로 읽을 수 있으며, 내장 코드 에디터와 24/7 AI 튜터와 함께 브라우저에서 직접 실습할 수 있습니다. 이 강의는 Docker & Kubernetes for Developers 학습 경로의 일부이며, 진행 상황이 웹과 CoddyKit 앱에 동기화됩니다. Docker & Kubernetes for Developers 강의에는 총 4개의 강의가 포함되어 있습니다.

이 강의의 일부는 아직 번역되지 않았으며 영어로 표시됩니다.

Stateful Applications in K8s

When deploying applications in Kubernetes, some applications are stateless, meaning they don't store data locally and can be easily scaled or replaced.

However, many critical applications, like databases or message queues, are stateful. They need persistent storage and stable network identities.

This lesson introduces StatefulSets, a Kubernetes API object designed specifically to manage these stateful workloads.

Why StatefulSets?

Traditional Kubernetes Deployments are great for stateless apps. They create Pods with arbitrary names and can replace them freely.

Stateful applications, however, require:

Stable, unique network identities: Each instance needs a consistent name.
Stable, persistent storage: Data must survive Pod restarts or rescheduling.
Ordered deployment and scaling: Sometimes, instances need to start or stop in a specific sequence.

StatefulSets provide these crucial capabilities.

Key Features of StatefulSets

StatefulSets offer several powerful features for managing stateful applications:

Stable Network ID: Each Pod gets a predictable name (e.g., web-0, web-1) and DNS hostname.
Stable Persistent Storage: Integrates with Persistent Volumes (PVs) and Persistent Volume Claims (PVCs) to give each Pod its own persistent storage.
Ordered Guarantees: Ensures Pods are created, scaled, and deleted in a strict, ordinal order.
Graceful Deployment: Pods are only created after their storage is ready, and only deleted after they've gracefully shut down.

StatefulSet Components

A StatefulSet typically works in conjunction with other Kubernetes resources:

Headless Service: Provides stable network identities for the Pods. It doesn't load-balance traffic, but creates unique DNS entries for each Pod.
Pod Template: Defines the specification for the Pods, including containers, resources, etc.
Volume Claim Templates: Generates a unique Persistent Volume Claim (PVC) for each Pod, ensuring dedicated storage.

Defining a Headless Service

Before creating a StatefulSet, you often define a Headless Service. This service is crucial for assigning stable network identities to your stateful Pods.

Notice clusterIP: None, which tells Kubernetes not to assign a cluster IP, making it 'headless'.

apiVersion: v1
kind: Service
metadata:
  name: my-app-service
  labels:
    app: my-app
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None # This makes it a Headless Service
  selector:
    app: my-app

Creating a Basic StatefulSet

Now, let's look at a basic StatefulSet definition. It links to our Headless Service using serviceName and defines a volumeClaimTemplates for persistent storage.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: my-app
spec:
  serviceName: "my-app-service" # Link to Headless Service
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 1Gi

Understanding Pod Identity

When the StatefulSet from the previous scene is deployed, it will create three Pods named my-app-0, my-app-1, and my-app-2.

Each Pod also gets its own stable DNS entry, like my-app-0.my-app-service.default.svc.cluster.local. This allows other services to reliably connect to specific instances.

Crucially, each Pod will also get its own unique Persistent Volume Claim (e.g., www-my-app-0), ensuring dedicated storage.

Ordered Deployment & Scaling

StatefulSets enforce a strict order for Pod creation, scaling, and deletion. This is vital for applications where sequence matters (e.g., a primary database and its replicas).

Creation: Pods are created in ascending ordinal order (my-app-0, then my-app-1, etc.). Each Pod is fully running and ready before the next is created.
Deletion: Pods are terminated in descending ordinal order (my-app-2, then my-app-1, etc.). Each Pod is fully shut down before the next is deleted.
Scaling: Similarly, scaling up adds Pods in order, and scaling down removes them in reverse order.

Updating StatefulSets

StatefulSets support controlled updates to their Pods, typically used for rolling out new versions of your application.

RollingUpdate (default): Pods are updated in reverse ordinal order (my-app-2, then my-app-1, etc.). Each Pod is updated and ready before the next one starts.
OnDelete: This strategy requires manual intervention. The StatefulSet controller will not automatically update Pods. You must manually delete Pods for the new template to take effect.

Rolling updates ensure minimal downtime and maintain the application's state during upgrades.

StatefulSet Features Check

Which of the following are key characteristics or requirements for Kubernetes StatefulSets?

StatefulSets Recap

Congratulations! You've learned about Kubernetes StatefulSets.

StatefulSets manage stateful applications, ensuring stable identities and persistent storage.
They provide stable network IDs, ordered operations, and leverage Volume Claim Templates for dedicated storage.
A Headless Service is often used to provide stable DNS entries for StatefulSet Pods.
They support controlled updates with strategies like RollingUpdate.

StatefulSets are essential for running databases, message queues, and other stateful services reliably on Kubernetes.

자주 묻는 질문

“StatefulSets를 활용한 상태 저장 애플리케이션 관리” 강의는 무료인가요?

네 — “StatefulSets를 활용한 상태 저장 애플리케이션 관리” 전체 내용을 이 웹사이트에서 무료로 읽을 수 있습니다. 인터랙티브하게 실습하려면(내장 코드 에디터와 24/7 AI 튜터), CoddyKit PRO로 업그레이드하면 Docker & Kubernetes for Developers 강의 전체를 잠금 해제할 수 있습니다. Docker & Kubernetes for Developers 강의에는 총 4개의 강의가 포함되어 있습니다.

“StatefulSets를 활용한 상태 저장 애플리케이션 관리”에서 뭘 배우나요?

StatefulSets를 사용해 데이터베이스와 같은 상태 저장 애플리케이션을 배포하고 관리하며 안정적인 네트워크 ID와 영구 스토리지를 보장합니다. 브라우저에서 직접 실행하는 실습 코드로 Docker & Kubernetes for Developers을(를) 배우며, 24/7 AI 튜터가 강의를 진행하면서 질문에 답변해줍니다.

Docker & Kubernetes for Developers을(를) 시작하는 데 경험이 필요한가요?

사전 경험은 필요하지 않습니다. CoddyKit의 Docker & Kubernetes for Developers은(는) 초급자부터 고급 학습자까지를 위해 구성되어 있으므로, 여기서 시작하거나 처음부터 시작할 수 있으며 자신의 속도대로 진행할 수 있습니다. 이것은 4개 중 2번째 강의입니다.

“StatefulSets를 활용한 상태 저장 애플리케이션 관리” 강의는 얼마나 걸리나요?

대부분의 CoddyKit 강의는 약 5~10분이 소요됩니다. 각 강의는 간결하고 인터랙티브하여 꾸준한 진행이 가능하며, 웹과 앱에서 중단한 부분부터 바로 시작할 수 있습니다.

이 Docker & Kubernetes for Developers 강의에서 코드를 작성하고 실행할 수 있나요?

네. 모든 Docker & Kubernetes for Developers 강의에는 내장 코드 에디터가 포함되어 있으므로, 브라우저에서 바로 실제 코드를 작성하고 실행한 후 즉시 AI 피드백을 받을 수 있습니다 — 로컬 설정이 필요 없습니다.

이 강의의 모든 강의

← Docker & Kubernetes for Developers(으)로 돌아가기