cat <<EOF > /tmp/pending-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: resource-hungry
  namespace: pod-lab
spec:
  containers:
  - name: app
    image: nginx:alpine
    resources:
      requests:
        memory: "100Ti"  # 터무니없이 큰 메모리 요청
        cpu: "1000"
EOF

kubectl apply -f /tmp/pending-pod.yaml

# 상태 확인
kubectl get pod resource-hungry -n pod-lab
# NAME             READY   STATUS    RESTARTS   AGE
# resource-hungry  0/1     Pending   0          30s

# 원인 확인
kubectl describe pod resource-hungry -n pod-lab | grep -A5 Events
# Warning  FailedScheduling  ... 0/1 nodes are available: 1 Insufficient memory.

kubectl delete pod resource-hungry -n pod-lab

cat <<EOF > /tmp/crash-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: crash-test
  namespace: pod-lab
spec:
  containers:
  - name: crash-app
    image: alpine
    command: ["sh", "-c", "echo 'Starting...'; echo 'DB_HOST is: '$DB_HOST; exit 1"]
    env:
    - name: DB_HOST
      value: ""
EOF

kubectl apply -f /tmp/crash-pod.yaml

# 잠시 후 상태 확인
sleep 15
kubectl get pod crash-test -n pod-lab
# NAME         READY   STATUS             RESTARTS   AGE
# crash-test   0/1     CrashLoopBackOff   2          30s

# 진단 Step 1: 현재 로그
kubectl logs crash-test -n pod-lab
# Starting...
# DB_HOST is:
# ← DB_HOST가 비어있어서 exit 1

# 진단 Step 2: 이전 컨테이너 로그 (이미 죽었을 때)
kubectl logs crash-test -n pod-lab --previous

# 진단 Step 3: describe로 재시작 횟수와 이벤트
kubectl describe pod crash-test -n pod-lab | grep -E "Restart Count|Exit Code|Events" -A5

kubectl delete pod crash-test -n pod-lab

cat <<EOF > /tmp/bad-image-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: bad-image
  namespace: pod-lab
spec:
  containers:
  - name: app
    image: nginx:this-tag-does-not-exist-xyz
EOF

kubectl apply -f /tmp/bad-image-pod.yaml

sleep 10
kubectl get pod bad-image -n pod-lab
# NAME        READY   STATUS             RESTARTS   AGE
# bad-image   0/1     ImagePullBackOff   0          10s

# 원인 확인
kubectl describe pod bad-image -n pod-lab | grep -A10 Events
# Warning  Failed  ... Failed to pull image "nginx:this-tag-does-not-exist-xyz":
#   rpc error: ... manifest for nginx:this-tag-does-not-exist-xyz not found

kubectl delete pod bad-image -n pod-lab

cat <<EOF > /tmp/probe-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: probe-test
  namespace: pod-lab
spec:
  containers:
  - name: nginx
    image: nginx:alpine
    ports:
    - containerPort: 80
    livenessProbe:
      httpGet:
        path: /
        port: 80
      initialDelaySeconds: 5
      periodSeconds: 5
    readinessProbe:
      httpGet:
        path: /
        port: 80
      initialDelaySeconds: 3
      periodSeconds: 3
EOF

kubectl apply -f /tmp/probe-pod.yaml

# 시작 직후 (아직 readiness 미통과)
kubectl get pod probe-test -n pod-lab
# NAME         READY   STATUS    RESTARTS   AGE
# probe-test   0/1     Running   0          3s

# 잠시 후 (readiness 통과)
sleep 10
kubectl get pod probe-test -n pod-lab
# NAME         READY   STATUS    RESTARTS   AGE
# probe-test   1/1     Running   0          10s

kubectl delete pod probe-test -n pod-lab