실습

Manual Scheduling

Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx
    name: nginx
  nodeName: worker-1
EOF

Pod 상태 확인
```
kubectl get pod nginx
```

위의 명령어를 실행하면 아래와 같은 결과를 확인할수 있습니다.

NAME         READY   STATUS    RESTARTS   AGE
nginx        0/1     Pending   0          4s

1분 정도 시간이 지난후에 Pod 상태를 확인
```
kubectl get pod nginx
```
Kubernetes 공식문서 리뷰 - https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#nodename
Pod Garbage Collector 코드 리뷰 - https://github.com/kubernetes/kubernetes/blob/master/pkg/controller/podgc/gc_controller.go#L212
노드 목록 확인
```
kubectl get node
```

spec.nodeName에 위의 명령어의 결과로 나온 첫번째 노드 이름을 넣고 Pod를 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx
    name: nginx
  nodeName: $(kubectl get node -o=jsonpath='{.items[0].metadata.name}')
EOF

Pod 상태 확인
```
kubectl get pod nginx
```

spec.nodeName을 명시하지 않고 Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: httpd
spec:
  containers:
  - image: httpd
    name: httpd
EOF

spec.nodeName을 명시하지 않고 생성한 Pod에 발생한 Event 확인
```
kubectl describe pod httpd
```
spec.nodeName을 명시하고 생성한 Pod에 발생한 Event 확인
```
kubectl describe pod nginx
```
Pod 삭제
```
kubectl delete pod nginx httpd
```

Node Selector

Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx
    name: nginx
  nodeSelector:
    env: dev
EOF

Pod 상태 확인
```
kubectl get pod nginx
```

위의 명령어를 실행하면 아래와 같은 결과를 확인할수 있습니다.

NAME          READY   STATUS    RESTARTS   AGE
nginx         0/1     Pending   0          16s

아래의 명령어를 사용해서 Pod가 배포되지 않는 이유를 찾으세요.
```
kubectl describe pod nginx
```
Node에 부여된 Label 확인
```
kubectl get node --show-labels
```

두번째 노드에 키(Key)는 env 이고 값(Value)은 dev 인 Label 부여

kubectl label node \
$(kubectl get node -o=jsonpath='{.items[1].metadata.name}') env=dev

Node에 Label이 부여되었는지 확인

kubectl get node --show-labels | grep -E 'env=dev|$'

Pending 상태였던 Pod가 배포됐는지 확인
```
kubectl get pod nginx
```
Pod에 발생한 Event 확인
```
kubectl describe pod nginx
```

Node에 부여한 Label 삭제

kubectl label node \
$(kubectl get node -o=jsonpath='{.items[1].metadata.name}') env-

Node에 Label이 삭제되었는지 확인

kubectl get node --show-labels | grep -E 'env=dev|$'

Pod 상태 확인
```
kubectl get pod nginx
```
Pod 삭제
```
kubectl delete pod nginx
```

Node Affinity

Node에 부여된 Label 확인
```
kubectl get node --show-labels
```

각 Node의 가용영역 확인

kubectl get nodes --label-columns topology.kubernetes.io/zone

Pod 생성

for i in {1..4}
do
  cat <<EOF | kubectl apply -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: nginx-${i}
    labels:
      app: nginx
  spec:
    containers:
    - image: nginx
      name: nginx
      resources:
        requests:
          cpu: 0.5
    affinity:
      nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
          - matchExpressions:
            - key: topology.kubernetes.io/zone
              operator: In
              values:
              - ap-northeast-2a
              - ap-northeast-2b
        preferredDuringSchedulingIgnoredDuringExecution:
        - weight: 100
          preference:
            matchExpressions:
            - key: topology.kubernetes.io/zone
              operator: In
              values:
              - ap-northeast-2a
        - weight: 1
          preference:
            matchExpressions:
            - key: topology.kubernetes.io/zone
              operator: In
              values:
              - ap-northeast-2b
EOF
done

Pod가 배포된 노드 확인
```
kubectl get pod -l app=nginx -o wide
```

Node의 가용영역 확인

kubectl get nodes --label-columns topology.kubernetes.io/zone

각각의 Pod가 어떤 절차에 의해서 각각의 Node에 스케쥴링 되었는지 확인
Pod 삭제
```
kubectl delete pod -l app=nginx
```

아래의 YAML 파일에 명시된 spec.affinity가 의미하는 것을 설명하고 Pod 생성

for i in {1..4}
do
  cat <<EOF | kubectl apply -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: nginx-${i}
    labels:
      app: nginx
  spec:
    containers:
    - image: nginx
      name: nginx
      resources:
        requests:
          cpu: 0.5
    affinity:
      nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
          - matchExpressions:
            - key: topology.kubernetes.io/zone
              operator: NotIn
              values:
              - ap-northeast-2a
        preferredDuringSchedulingIgnoredDuringExecution:
        - weight: 100
          preference:
            matchExpressions:
            - key: topology.kubernetes.io/zone
              operator: NotIn
              values:
              - ap-northeast-2b
EOF
done

Pod가 배포된 노드 확인
```
kubectl get pod -l app=nginx -o wide
```
각각의 Pod가 어떤 절차에 의해서 각각의 Node에 스케쥴링 되었는지 확인
Pod 삭제
```
kubectl delete pod -l app=nginx
```

Pod Affinity

Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: mod-security
  labels:
    security: enhanced
    app: nginx
spec:
  containers:
  - name: modsecurity
    image: owasp/modsecurity:nginx-alpine
EOF

아래의 YAML 파일에 명시된 spec.template.spec.affinity가 의미하는 것을 설명하고 Deployment 생성

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
      affinity:
        podAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: security
                operator: In
                values:
                - enhanced
            topologyKey: kubernetes.io/hostname
EOF

Pod가 배포된 노드 확인
```
kubectl get pod -l app=nginx -o wide
```
Pod 삭제
```
kubectl delete pod mod-security
```
mod-security Pod가 삭제되어서 Deployment에 명시한 Affinity 규칙이 더 이상 성립되지 않습니다. 이 경우 어떤일이 발생하는지 설명하세요.
Deployment 삭제
```
kubectl delete deploy nginx
```

아래의 YAML 파일에 명시된 spec.template.spec.affinity가 의미하는 것을 설명하고 Deployment 생성

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis
  labels:
    app: cache
spec:
  selector:
    matchLabels:
      app: cache
  replicas: 4
  template:
    metadata:
      labels:
        app: cache
    spec:
      containers:
      - name: redis-server
        image: redis:3.2-alpine
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - cache
            topologyKey: kubernetes.io/hostname
EOF

Pod가 배포된 노드 확인
```
kubectl get pod -l app=cache -o wide
```

아래의 YAML 파일에 명시된 spec.template.spec.affinity가 의미하는 것을 설명하고 Deployment 생성

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
      affinity:
        podAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - cache
            topologyKey: kubernetes.io/hostname
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - nginx
            topologyKey: kubernetes.io/hostname
EOF

Pod가 배포된 노드 확인

kubectl get pod -l 'app in (nginx,cache)' -o wide

생성된 리소스 삭제

kubectl delete deploy -l 'app in (nginx,cache)'

Spread Pod Across Cluster

nodeSelector를 명시한 Pod 생성

for s in web api queue cache database
do
  cat <<EOF | kubectl apply -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: ${s}
    labels:
      app: myapp
  spec:
    nodeSelector:
      topology.kubernetes.io/zone: ap-northeast-2a
    containers:
    - image: busybox
      name: busybox
      command: ["/bin/sleep"]
      args: ["infinity"]
EOF
done

각 Pod가 배포된 Node 확인

kubectl get pod -l app=myapp -o wide -A --sort-by=.spec.nodeName

각 Node별로 배포된 Pod 갯수 확인

kubectl describe node | grep -E "(^Name:|^Non-terminated)"

nodeSelector를 명시하지 않은 Pod 생성

for i in {1..5}
do
  cat <<EOF | kubectl apply -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: nginx-${i}
    labels:
      app: nginx
  spec:
    containers:
    - image: nginx
      name: nginx
EOF
done

각 Pod가 배포된 Node 확인

kubectl get pod -l app=nginx -o wide --sort-by=.spec.nodeName

각 Node별로 배포된 Pod 갯수 확인

kubectl describe node | grep -E "(^Name:|^Non-terminated)"

위에서 nodeSelector를 명시하지 않고 생성한 Pod 삭제
```
kubectl delete pod -l app=nginx
```

각 Pod가 배포된 Node 확인

kubectl get pod -l app=myapp -o wide --sort-by=.spec.nodeName

각 Node별로 배포된 Pod 갯수 확인

kubectl describe node | grep -E "(^Name:|^Non-terminated)"

Deployment 생성

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 5
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
EOF

Deployment를 통해서 생성된 Pod들이 배포된 Node 확인
```
kubectl get pod -l app=nginx -o wide --sort-by=.spec.nodeName
```

EKS 설정창에서 Scheduler의 로깅을 활성화하면 CloudWatch를 통해서 아래와 같은 구성으로 kube-scheduler가 구동되는 것을 확인 가능

apiVersion: kubescheduler.config.k8s.io/v1beta1
clientConnection:
  acceptContentTypes: ""
  burst: 100
  contentType: application/vnd.kubernetes.protobuf
  kubeconfig: /etc/kubernetes/scheduler.conf
  qps: 50
enableContentionProfiling: true
enableProfiling: true
healthzBindAddress: 0.0.0.0:10251
kind: KubeSchedulerConfiguration
leaderElection:
  leaderElect: true
  leaseDuration: 15s
  renewDeadline: 10s
  resourceLock: leases
  resourceName: kube-scheduler
  resourceNamespace: kube-system
  retryPeriod: 2s
metricsBindAddress: 0.0.0.0:10251
parallelism: 16
percentageOfNodesToScore: 0
podInitialBackoffSeconds: 1
podMaxBackoffSeconds: 10
profiles:
- pluginConfig:
  - args:
      apiVersion: kubescheduler.config.k8s.io/v1beta1
      kind: DefaultPreemptionArgs
      minCandidateNodesAbsolute: 100
      minCandidateNodesPercentage: 10
    name: DefaultPreemption
  - args:
      apiVersion: kubescheduler.config.k8s.io/v1beta1
      hardPodAffinityWeight: 1
      kind: InterPodAffinityArgs
    name: InterPodAffinity
  - args:
      apiVersion: kubescheduler.config.k8s.io/v1beta1
      kind: NodeAffinityArgs
    name: NodeAffinity
  - args:
      apiVersion: kubescheduler.config.k8s.io/v1beta1
      kind: NodeResourcesFitArgs
    name: NodeResourcesFit
  - args:
      apiVersion: kubescheduler.config.k8s.io/v1beta1
      kind: NodeResourcesLeastAllocatedArgs
      resources:
      - name: cpu
        weight: 1
      - name: memory
        weight: 1
    name: NodeResourcesLeastAllocated
  - args:
      apiVersion: kubescheduler.config.k8s.io/v1beta1
      defaultingType: System
      kind: PodTopologySpreadArgs
    name: PodTopologySpread
  - args:
      apiVersion: kubescheduler.config.k8s.io/v1beta1
      bindTimeoutSeconds: 600
      kind: VolumeBindingArgs
    name: VolumeBinding
  plugins:
    bind:
      enabled:
      - name: DefaultBinder
        weight: 0
    filter:
      enabled:
      - name: NodeUnschedulable
        weight: 0
      - name: NodeName
        weight: 0
      - name: TaintToleration
        weight: 0
      - name: NodeAffinity
        weight: 0
      - name: NodePorts
        weight: 0
      - name: NodeResourcesFit
        weight: 0
      - name: VolumeRestrictions
        weight: 0
      - name: EBSLimits
        weight: 0
      - name: GCEPDLimits
        weight: 0
      - name: NodeVolumeLimits
        weight: 0
      - name: AzureDiskLimits
        weight: 0
      - name: VolumeBinding
        weight: 0
      - name: VolumeZone
        weight: 0
      - name: PodTopologySpread
        weight: 0
      - name: InterPodAffinity
        weight: 0
    permit: {}
    postBind: {}
    postFilter:
      enabled:
      - name: DefaultPreemption
        weight: 0
    preBind:
      enabled:
      - name: VolumeBinding
        weight: 0
    preFilter:
      enabled:
      - name: NodeResourcesFit
        weight: 0
      - name: NodePorts
        weight: 0
      - name: PodTopologySpread
        weight: 0
      - name: InterPodAffinity
        weight: 0
      - name: VolumeBinding
        weight: 0
      - name: NodeAffinity
        weight: 0
    preScore:
      enabled:
      - name: InterPodAffinity
        weight: 0
      - name: PodTopologySpread
        weight: 0
      - name: TaintToleration
        weight: 0
      - name: NodeAffinity
        weight: 0
    queueSort:
      enabled:
      - name: PrioritySort
        weight: 0
    reserve:
      enabled:
      - name: VolumeBinding
        weight: 0
    score:
      enabled:
      - name: NodeResourcesBalancedAllocation
        weight: 1
      - name: ImageLocality
        weight: 1
      - name: InterPodAffinity
        weight: 1
      - name: NodeResourcesLeastAllocated
        weight: 1
      - name: NodeAffinity
        weight: 1
      - name: NodePreferAvoidPods
        weight: 10000
      - name: PodTopologySpread
        weight: 2
      - name: TaintToleration
        weight: 1
  schedulerName: default-scheduler

Pod Topology Spread Constraints 및 Default Pod Topology Spread 리뷰
Deployment 삭제
```
kubectl delete deploy nginx
```

각 Node별로 배포된 Pod 갯수 확인

kubectl describe node | grep -E "(^Name:|^Non-terminated)"

podAntiAffinity를 명시하고 Pod 생성

for i in {1..5}
do
  cat <<EOF | kubectl apply -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: nginx-${i}
    labels:
      app: nginx
  spec:
    affinity:
      podAntiAffinity:
        preferredDuringSchedulingIgnoredDuringExecution:
        - weight: 100
          podAffinityTerm:
            labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - nginx
            topologyKey: kubernetes.io/hostname
    containers:
    - image: nginx
      name: nginx
EOF
done

위에서 생성한 Pod들이 배포된 Node 확인

kubectl get pod -l app=nginx -o wide --sort-by=.spec.nodeName

위에서 생성한 Pod 삭제
```
kubectl delete pod -l app=nginx
```

topologySpreadConstraints를 명시하고 Pod 생성

for i in {1..5}
do
  cat <<EOF | kubectl apply -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: nginx-${i}
    labels:
      app: nginx
  spec:
    topologySpreadConstraints:
    - maxSkew: 3
      topologyKey: topology.kubernetes.io/zone
      whenUnsatisfiable: ScheduleAnyway
      labelSelector:
        matchLabels:
          app: nginx
    containers:
    - image: nginx
      name: nginx
EOF
done

위에서 생성한 Pod들이 배포된 Node 확인

kubectl get pod -l app=nginx -o wide --sort-by=.spec.nodeName

리소스 삭제

kubectl delete pod -l 'app in (nginx,myapp)'

Requests & Limits

Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx
    name: nginx
    resources:
      requests:
        cpu: 2
EOF

Pod 상태 확인
```
kubectl get pod nginx
```

위의 명령어를 실행하면 아래와 같은 결과를 확인할수 있습니다.

NAME            READY   STATUS    RESTARTS   AGE
nginx           0/1     Pending   0          8s

아래의 명령어를 사용해서 Pod가 배포되지 않는 이유를 찾으세요.
```
kubectl describe pod nginx
```

노드의 상태의 상세값들을 확인

kubectl get node -o=jsonpath='{.items[*].status}' | jq

위에서 확인한 값들중에서 allocatable.cpu가 무엇을 의미하는지 확인 - https://kubernetes.io/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable
```
kubectl explain node.status.allocatable.cpu
```

노드별로 할당 가용한 CPU 리소스를 확인

kubectl get node -o custom-columns=NAME:.metadata.name,ALLOCATABLE_CPU:.status.allocatable.cpu

Pending 상태인 Pod를 삭제
```
kubectl delete pod nginx
```

노드에 할당 가용한 최대 CPU 값을 spec.container.resources.requests.cpu에 넣고 Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx
    name: nginx
    resources:
      limits:
        cpu: $(kubectl get node -o=jsonpath='{.items[0].status.allocatable.cpu}')
EOF

Pod가 배포되는지 확인하고 만약 배포되지 않는다면 그 이유를 확인
```
kubectl get pod nginx
```
Pod 삭제
```
kubectl delete pod nginx
```

하나의 노드에 키(Key)는 env 이고 값(Value)은 dev 인 Label 부여

kubectl label node \
$(kubectl get node -o=jsonpath='{.items[0].metadata.name}') env=dev

Node에 Label이 부여되었는지 확인

kubectl get node --show-labels | grep -E 'env=dev|$'

Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: stress-1
  labels:
    app: stress
spec:
  containers:
  - image: lorel/docker-stress-ng
    name: stress-ng
    args:
      - --cpu
      - "2"
  nodeSelector:
    env: dev
---
apiVersion: v1
kind: Pod
metadata:
  name: stress-2
  labels:
    app: stress
spec:
  containers:
  - image: lorel/docker-stress-ng
    name: stress-ng
    args:
      - --cpu
      - "2"
    resources:
      requests:
        cpu: 0.5
      limits:
        cpu: 1
  nodeSelector:
    env: dev
---
apiVersion: v1
kind: Pod
metadata:
  name: stress-3
  labels:
    app: stress
spec:
  containers:
  - image: lorel/docker-stress-ng
    name: stress-ng
    args:
      - --cpu
      - "2"
    resources:
      limits:
        cpu: 1
  nodeSelector:
    env: dev
EOF

Pod가 생성됐는지 확인
```
kubectl get pod -l app=stress
```

Metric Server 설치

kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

Pod들의 CPU 사용량 확인

kubectl top pod -l app=stress --use-protocol-buffers

노드별로 할당 가용한 Memory 리소스 확인

kubectl get node \
-o custom-columns=NAME:.metadata.name,ALLOCATABLE_MEMORY:.status.allocatable.memory

Pod 재생성

cat <<EOF | kubectl replace --force --grace-period=0 -f -
apiVersion: v1
kind: Pod
metadata:
  name: stress-1
  labels:
    app: stress
spec:
  containers:
  - image: lorel/docker-stress-ng
    name: stress-ng
    args:
      - --vm
      - "1"
      - --vm-bytes
      - "1G"
      - --vm-method 
      - all
  nodeSelector:
    env: dev
---
apiVersion: v1
kind: Pod
metadata:
  name: stress-2
  labels:
    app: stress
spec:
  containers:
  - image: lorel/docker-stress-ng
    name: stress-ng
    args:
      - --vm
      - "1"
      - --vm-bytes
      - "1G"
      - --vm-method 
      - all
    resources:
      requests:
        memory: 200Mi
      limits:
        memory: 1Gi
  nodeSelector:
    env: dev
---
apiVersion: v1
kind: Pod
metadata:
  name: stress-3
  labels:
    app: stress
spec:
  containers:
  - image: lorel/docker-stress-ng
    name: stress-ng
    args:
      - --vm
      - "1"
      - --vm-bytes
      - "1G"
      - --vm-method 
      - all
    resources:
      limits:
        cpu: 0.5
        memory: 1Gi
  nodeSelector:
    env: dev
EOF

Pod가 생성되었는지 확인
```
kubectl get pod -l app=stress
```
Metrics Server가 60초 마다 지표를 수집하기 때문에 2-3분 정도 대기 - https://github.com/kubernetes-sigs/metrics-server/blob/master/FAQ.md#how-often-metrics-are-scraped
```
sleep 180
```

Pod들의 메모리 사용량 확인

kubectl top pod -l app=stress --use-protocol-buffers

Pod가 배포된 Node에 발생한 Event 확인

kubectl describe node $(kubectl get pod -l app=stress \
-o=jsonpath='{.items[0].spec.nodeName}')

Pod의 상태가 OOMKilled가 될때까지 2-3분간 대기
```
sleep 180
```
Pod 상태 확인
```
kubectl get pod -l app=stress
```

상태가 Running이 아닌 Pod가 있으면 원인을 확인

kubectl get pod -l app=stress \
-o custom-columns=NAME:metadata.name,\
STATUS:status.phase,REASON:status.reason,MESSAGE:status.message

각 Pod별 QoS 클래스 확인

kubectl get pod -l app=stress \
-o custom-columns=NAME:.metadata.name,\
STATUS:status.phase,QoS:.status.qosClass

각 QoS 클래스가 의미하는것을 확인 - https://kubernetes.io/docs/concepts/scheduling-eviction/node-pressure-eviction/#pod-selection-for-kubelet-eviction

Pod가 배포된 Node에 발생한 Event 확인

kubectl describe node $(kubectl get pod -l app=stress \
-o=jsonpath='{.items[0].spec.nodeName}')

새로운 터미널을 열고 Pod가 배포된 Node의 인스턴스 ID를 확인하고 환경변수로 지정

{
    export INSTANCE_ID=$(kubectl get node $(kubectl get pod -l app=stress \
    -o=jsonpath='{.items[0].spec.nodeName}') \
    -o jsonpath='{.spec.providerID}{"\n"}' | grep -oE "i-[a-z0-9]+")
    echo $INSTANCE_ID
}

Pod가 배포된 Node로 Session Manager 연결
```
aws ssm start-session --target $INSTANCE_ID
```
커널 로그에서 OOM 관련된 내용이 있는지 확인 - https://kubernetes.io/docs/concepts/scheduling-eviction/node-pressure-eviction/#node-out-of-memory-behavior
```
sudo tail -n 1000 /var/log/messages | grep -i oom
```
Session Manager 종료
```
exit
```

리소스 삭제

{
    kubectl delete pod -l app=stress
    kubectl label node env- --all
    kubectl delete -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
}

Taints & Tolerations

Pod 생성

for i in {1..10}
do
  cat <<EOF | kubectl apply -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: nginx-${i}
    labels:
      app: nginx
  spec:
    containers:
    - image: nginx
      name: nginx
EOF
done

Pod가 배포된 Node 확인

kubectl get pod -l app=nginx -o wide --sort-by=.spec.nodeName

Node 목록 확인
```
kubectl get node
```

첫번째 Node에 Taint 부여

kubectl taint nodes $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
status=unstable:PreferNoSchedule

Node에 부여된 Taint 확인

kubectl get nodes -o=custom-columns=NodeName:.metadata.name,\
TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,\
TaintEffect:.spec.taints[*].effect

Pod 재생성

for i in {1..10}
do
  kubectl get pod nginx-${i} -o yaml | kubectl replace --force -f -
done

Pod가 배포된 Node 확인

kubectl get pod -l app=nginx -o wide --sort-by=.spec.nodeName

첫번째 Node에 부여한 Taint 삭제

kubectl taint nodes $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
status-

Node에 부여된 Taint 확인

kubectl get nodes -o=custom-columns=NodeName:.metadata.name,\
TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,\
TaintEffect:.spec.taints[*].effect

두번째 Node에 Taint 부여

kubectl taint nodes $(kubectl get node -o=jsonpath='{.items[1].metadata.name}') \
status=maintenance:NoSchedule

Node에 부여된 Taint 확인

kubectl get nodes -o=custom-columns=NodeName:.metadata.name,\
TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,\
TaintEffect:.spec.taints[*].effect

Pod 삭제
```
kubectl delete pod -l app=nginx
```

Deployment 생성

kubectl create deploy nginx --image=nginx --replicas=10

위에서 생성한 Deployment를 통해서 생성된 Pod가 배포된 Node 확인
```
kubectl get pod -l app=nginx -o wide --sort-by=.spec.nodeName
```

Deployment 재생성

cat <<EOF | kubectl replace --force -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 10
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      tolerations:
      - key: status
        operator: Equal
        value: maintenance
        effect: NoSchedule
      containers:
      - name:  nginx
        image: nginx
EOF

위에서 재생성한 Deployment를 통해서 생성된 Pod가 배포된 Node 확인
```
kubectl get pod -o wide --sort-by=.spec.nodeName
```
Node에 Taint가 부여되어 있고 PodSpec에 Toleration이 설정되어 있을 경우에 어떤 절차를 통해서 Pod가 Node에 스케쥴링 되는지 확인

두번째 Node에 부여한 Taint 삭제

kubectl taint nodes $(kubectl get node -o=jsonpath='{.items[1].metadata.name}') \
status-

Node에 부여된 Taint 확인

kubectl get nodes -o=custom-columns=NodeName:.metadata.name,\
TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,\
TaintEffect:.spec.taints[*].effect

Deployment 생성

kubectl get deploy nginx -o yaml | kubectl replace --force -f -

위에서 재생성한 Deployment를 통해서 생성된 Pod가 배포된 Node 확인
```
kubectl get pod -o wide --sort-by=.spec.nodeName
```

첫번째 Node에 Taint 부여

kubectl taint nodes $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
status=upgrading:NoExecute

첫번째 Node에 Label 부여

kubectl label nodes $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
tainted=yes

Node에 부여된 Taint 확인

kubectl get nodes -o=custom-columns=NodeName:.metadata.name,\
TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,\
TaintEffect:.spec.taints[*].effect

Taint가 부여된 Node에 배포되었던 Pod가 삭제되고 다른 Node에 새로운 Pod가 생겼는지 확인 - 리소스가 부족할 경우 Pending 상태가 될수도 있음
```
kubectl get pod -o wide --sort-by=.spec.nodeName
```

nodeSelector를 명시한 Pod 생성

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: emergency
spec:
  containers:
  - name: nginx
    image: nginx
  nodeSelector:
    tainted: "yes"
EOF

Pod가 생성되는지 확인
```
kubectl get pod emergency
```
Pod가 생성되지 않으면 그 이유를 확인
```
kubectl describe pod emergency
```

Pod에 toleration 명시 - 60초 동안만 toleration 유지

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: emergency
spec:
  containers:
  - name: nginx
    image: nginx
  nodeSelector:
    tainted: "yes"
  tolerations:
  - key: status
    operator: Equal
    value: upgrading
    effect: NoExecute
    tolerationSeconds: 60
EOF

Pod가 생성되는지 확인
```
kubectl get pod emergency
```
60초가 지난 후에도 Pod가 존재하는지 확인
```
kubectl get pod emergency
```

노드에 부여한 Taint 삭제

kubectl taint nodes $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
status-

생성된 Pod들이 Taint가 삭제된 Node로 옮겨가거나 Pending 상태의 Pod들이 Taint가 삭제된 Node에 생성되는지 확인
```
kubectl get pod -l app=nginx
```
Deployment 삭제
```
kubectl delete deployment nginx
```

Descheduler

Cluster Autoscaler 가 실행중인 경우에는 해당 실습이 정상적으로 수행되지 않을수도 있으니 아래의 명령어로 Cluster Autoscaler 정지
```
kubectl -n kube-system scale deployment cluster-autoscaler --replicas=0
```

Deployment 생성

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 6
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        resources:
          requests:
            cpu: 100m
            memory: 100Mi
EOF

생성된 Pod 확인

kubectl get pods -l app=nginx -o wide --sort-by=spec.nodeName

첫번째 Node에 있는 Pod를 다른 Node로 강제 이동

kubectl drain $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
--pod-selector=app=nginx

재배포된 Pod 확인

kubectl get pods -o wide --sort-by=spec.nodeName

Node에 부여된 Taint 확인 - 3번 명령어에서 명시된 Node에 node.kubernetes.io/unschedulable:NoSchedule Taint가 부여됨

kubectl get nodes -o=custom-columns=NodeName:.metadata.name,\
TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,\
TaintEffect:.spec.taints[*].effect

Taint 제거

kubectl uncordon $(kubectl get node -o=jsonpath='{.items[0].metadata.name}')

Node에 부여된 Taint 확인

kubectl get nodes -o=custom-columns=NodeName:.metadata.name,\
TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,\
TaintEffect:.spec.taints[*].effect

Descheduler 실행

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
  name: descheduler-policy-configmap
  namespace: kube-system
data:
  policy.yaml: |
    apiVersion: descheduler/v1alpha1
    kind: DeschedulerPolicy
    strategies:
      LowNodeUtilization:
        enabled: true
        params:
          nodeResourceUtilizationThresholds:
            thresholds:
              cpu: 30
              memory: 30
              pods: 50
            targetThresholds:
              cpu: 70
              memory: 70
              pods: 80
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: descheduler-cluster-role
rules:
- apiGroups: [""]
  resources: ["events"]
  verbs: ["create", "update"]
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["get", "watch", "list"]
- apiGroups: [""]
  resources: ["namespaces"]
  verbs: ["get", "list"]
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get", "watch", "list", "delete"]
- apiGroups: [""]
  resources: ["pods/eviction"]
  verbs: ["create"]
- apiGroups: ["scheduling.k8s.io"]
  resources: ["priorityclasses"]
  verbs: ["get", "watch", "list"]
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: descheduler-sa
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: descheduler-cluster-role-binding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: descheduler-cluster-role
subjects:
  - name: descheduler-sa
    kind: ServiceAccount
    namespace: kube-system
---
apiVersion: batch/v1
kind: Job
metadata:
  name: descheduler-job
  namespace: kube-system
spec:
  parallelism: 1
  completions: 1
  template:
    metadata:
      name: descheduler-pod
    spec:
      priorityClassName: system-cluster-critical
      containers:
        - name: descheduler
          image: k8s.gcr.io/descheduler/descheduler:v0.21.0
          volumeMounts:
          - mountPath: /policy-dir
            name: policy-volume
          command:
            - "/bin/descheduler"
          args:
            - "--policy-config-file"
            - "/policy-dir/policy.yaml"
            - "--v"
            - "3"
          securityContext:
            allowPrivilegeEscalation: false
            capabilities:
              drop:
                - ALL
            privileged: false
            readOnlyRootFilesystem: true
            runAsNonRoot: true
      restartPolicy: "Never"
      serviceAccountName: descheduler-sa
      volumes:
      - name: policy-volume
        configMap:
          name: descheduler-policy-configmap
EOF

Descheduler Job 상태 확인

kubectl get job descheduler-job -n kube-system

Descheduler Job 로그 확인

kubectl -n kube-system logs job/descheduler-job

재배포된 Pod 확인

kubectl get pods -o wide --sort-by="{.spec.nodeName}"

Descheduler Job 삭제

kubectl -n kube-system delete job descheduler-job

Deployment 삭제
```
kubectl delete deploy nginx
```
Node에 부여된 Label 확인
```
kubectl get node --show-labels
```

하나의 노드에 키(Key)는 env 이고 값(Value)은 test 인 Label 부여

kubectl label node $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
env=test

Label이 정상적으로 부여 됐는지 확인
```
kubectl get node --show-labels | grep env=test
```

Deployment 생성

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: env
                operator: In
                values:
                - test
      containers:
      - image: nginx
        name: nginx
EOF

생성된 Pod가 env=test Label을 부여한 노드에 배포 됐는지 확인
```
kubectl get pods -o wide
```

15번에서 env=test Label을 부여한 노드에서 해당 Label 삭제

kubectl label node $(kubectl get node -o=jsonpath='{.items[0].metadata.name}') \
env-

Label이 정상적으로 삭제 되었는지 확인
```
kubectl get node --show-labels | grep env=test
```
기존에 생성된 Pod에 변경사항이 있는지 확인
```
kubectl get pods -o wide
```

다른 노드에 키(Key)는 env 이고 값(Value)은 test 인 Label 부여

kubectl label node $(kubectl get node -o=jsonpath='{.items[1].metadata.name}') \
env=test

Label이 정상적으로 부여 됐는지 확인
```
kubectl get node --show-labels | grep env=test
```
기존에 생성된 Pod에 변경사항이 있는지 확인
```
kubectl get pods -o wide
```

Descheduler 실행

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
  name: descheduler-policy-configmap
  namespace: kube-system
data:
  policy.yaml: |
    apiVersion: descheduler/v1alpha1
    kind: DeschedulerPolicy
    strategies:
      RemovePodsViolatingNodeAffinity:
        enabled: true
        params:
          nodeAffinityType:
          - requiredDuringSchedulingIgnoredDuringExecution
---
apiVersion: batch/v1
kind: Job
metadata:
  name: descheduler-job
  namespace: kube-system
spec:
  parallelism: 1
  completions: 1
  template:
    metadata:
      name: descheduler-pod
    spec:
      priorityClassName: system-cluster-critical
      containers:
        - name: descheduler
          image: k8s.gcr.io/descheduler/descheduler:v0.21.0
          volumeMounts:
          - mountPath: /policy-dir
            name: policy-volume
          command:
            - "/bin/descheduler"
          args:
            - "--policy-config-file"
            - "/policy-dir/policy.yaml"
            - "--v"
            - "3"
          securityContext:
            allowPrivilegeEscalation: false
            capabilities:
              drop:
                - ALL
            privileged: false
            readOnlyRootFilesystem: true
            runAsNonRoot: true
      restartPolicy: "Never"
      serviceAccountName: descheduler-sa
      volumes:
      - name: policy-volume
        configMap:
          name: descheduler-policy-configmap
EOF

Descheduler Job 상태 확인

kubectl get job descheduler-job -n kube-system

Descheduler Job 로그 확인

kubectl -n kube-system logs job/descheduler-job

Pod 상태 확인

kubectl get pods -o wide --sort-by="{.spec.nodeName}"

리소스 삭제

{
    kubectl delete job descheduler-job -n kube-system
    kubectl delete sa descheduler-sa -n kube-system
    kubectl delete clusterrole descheduler-cluster-role
    kubectl delete clusterrolebinding descheduler-cluster-role-binding
    kubectl delete deploy nginx
}

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Last updated 9 months ago