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Lab 6.1 - Volumes Efêmeros e emptyDir

Objetivos​

Ao final deste lab, você será capaz de:

  • Criar e usar volumes emptyDir
  • Utilizar volumes tmpfs (RAM)
  • Compartilhar volumes entre containers em um Pod
  • Compreender o ciclo de vida dos volumes efêmeros
  • Comparar emptyDir e tmpfs

Pré-requisitos​

  • Cluster Kubernetes funcional
  • kubectl configurado
  • Compreensão de Pods e volumes

Exercício 1: Volume emptyDir Básico​

Criar um Pod com emptyDir​

Crie pod-emptydir.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: emptydir-pod
spec:
  containers:
  - name: app
    image: busybox:1.35
    command: ["sh", "-c", "echo 'Hello' > /cache/data.txt && cat /cache/data.txt && sleep 3600"]
    volumeMounts:
    - name: cache
      mountPath: /cache
  volumes:
  - name: cache
    emptyDir: {}

Deploy e Verificação​

kubectl apply -f pod-emptydir.yaml
kubectl logs emptydir-pod
kubectl exec emptydir-pod -- ls -la /cache

Exercício 2: emptyDir com Limite de Tamanho​

Criar um Pod com Limite de Tamanho​

Crie pod-emptydir-limit.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: emptydir-limit-pod
spec:
  containers:
  - name: app
    image: busybox:1.35
    command: ["sh", "-c", "dd if=/dev/zero of=/cache/bigfile bs=1M count=100 && sleep 3600"]
    volumeMounts:
    - name: cache
      mountPath: /cache
  volumes:
  - name: cache
    emptyDir:
      sizeLimit: 50Mi

Deploy e Observação​

kubectl apply -f pod-emptydir-limit.yaml
kubectl get pod emptydir-limit-pod
# O Pod deve falhar pois 100Mi > 50Mi

Exercício 3: Volume Compartilhado entre Containers​

Criar um Pod Multi-Containers​

Crie pod-shared-volume.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: shared-volume-pod
spec:
  containers:
  - name: writer
    image: busybox:1.35
    command: ["sh", "-c", "echo 'Data from writer' > /shared/data.txt && sleep 3600"]
    volumeMounts:
    - name: shared
      mountPath: /shared
  - name: reader
    image: busybox:1.35
    command: ["sh", "-c", "sleep 5 && cat /shared/data.txt && sleep 3600"]
    volumeMounts:
    - name: shared
      mountPath: /shared
  volumes:
  - name: shared
    emptyDir: {}

Deploy e Verificação​

kubectl apply -f pod-shared-volume.yaml
kubectl logs shared-volume-pod -c writer
kubectl logs shared-volume-pod -c reader

Exercício 4: Volume tmpfs (RAM)​

Criar um Pod com tmpfs​

Crie pod-tmpfs.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: tmpfs-pod
spec:
  containers:
  - name: app
    image: busybox:1.35
    command: ["sh", "-c", "echo 'Fast storage' > /tmp/data.txt && cat /tmp/data.txt && sleep 3600"]
    volumeMounts:
    - name: tmpfs-volume
      mountPath: /tmp
  volumes:
  - name: tmpfs-volume
    emptyDir:
      medium: Memory
      sizeLimit: 100Mi

Deploy e Verificação​

kubectl apply -f pod-tmpfs.yaml
kubectl logs tmpfs-pod
kubectl exec tmpfs-pod -- df -h /tmp

Exercício 5: Comparação emptyDir vs tmpfs​

Criar Dois Pods para Comparação​

Crie pod-comparison.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: emptydir-bench
spec:
  containers:
  - name: app
    image: busybox:1.35
    command: ["sh", "-c", "time dd if=/dev/zero of=/cache/test bs=1M count=10 && sleep 3600"]
    volumeMounts:
    - name: cache
      mountPath: /cache
  volumes:
  - name: cache
    emptyDir: {}
---
apiVersion: v1
kind: Pod
metadata:
  name: tmpfs-bench
spec:
  containers:
  - name: app
    image: busybox:1.35
    command: ["sh", "-c", "time dd if=/dev/zero of=/tmp/test bs=1M count=10 && sleep 3600"]
    volumeMounts:
    - name: tmpfs-vol
      mountPath: /tmp
  volumes:
  - name: tmpfs-vol
    emptyDir:
      medium: Memory

Comparar Desempenho​

kubectl apply -f pod-comparison.yaml
kubectl logs emptydir-bench
kubectl logs tmpfs-bench
# Compare os tempos de escrita

Exercício 6: Caso de Uso Real - Cache​

Criar um Pod com Cache​

Crie pod-cache.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: cache-pod
spec:
  containers:
  - name: web-server
    image: nginx:1.20
    volumeMounts:
    - name: cache
      mountPath: /var/cache/nginx
  - name: cache-warmup
    image: busybox:1.35
    command: ["sh", "-c", "while true; do echo 'Cache data' > /cache/data.txt; sleep 60; done"]
    volumeMounts:
    - name: cache
      mountPath: /cache
  volumes:
  - name: cache
    emptyDir:
      sizeLimit: 500Mi

Deploy e Verificação​

kubectl apply -f pod-cache.yaml
kubectl exec cache-pod -c web-server -- ls -la /var/cache/nginx
kubectl exec cache-pod -c cache-warmup -- cat /cache/data.txt

Limpeza​

kubectl delete pod emptydir-pod emptydir-limit-pod shared-volume-pod tmpfs-pod emptydir-bench tmpfs-bench cache-pod

Perguntas para Reflexão​

  1. Qual é a principal diferença entre emptyDir e tmpfs?
  2. Quando você usaria tmpfs ao invés de emptyDir?
  3. Por que definir um sizeLimit para volumes emptyDir?
  4. O que acontece com os dados em um volume emptyDir quando o Pod é excluído?

Desafio Bônus​

Crie um Pod com três containers que compartilham um volume emptyDir:

  • Um container que escreve dados
  • Um container que lê e processa os dados
  • Um container que monitora o tamanho do volume

Lab criado em: Dezembro 2024