02.Scheduling - Resource Limits

LABS – CERTIFIED KUBERNETES ADMINISTRATOR WITH PRACTICE TESTS > SCHEDULING – Resource Limits

Scheduling

 

01. Manual Scheduling

02. Labels and Selectors

03. Taints and Tolerations

04. Node Affinity

05. Resource Limits

06. DaemonSets

07. Static PODs

08. Multiple Schedulers

01. A pod called rabbit is deployed. Identify the CPU requirements set on the Pod

in the current(default) namespace

 

정답 : 1

kubectl describe pod rabbit

 

02. Delete the rabbit Pod.

Once deleted, wait for the pod to fully terminate.

- Delete Pod rabbit

controlplane ~ ➜  kubectl delete pod rabbit
pod "rabbit" deleted

03. Another pod called elephant has been deployed in the default namespace.

It fails to get to a running state.

Inspect this pod and identify the Reason why it is not running.

1) Running

2) Ready

3) CrashLoopBackOff

! 4) OOMKilled (정답)

controlplane ~ ➜  kubectl describe pod elephant
Name:         elephant
Namespace:    default
Priority:     0
Node:         controlplane/172.25.0.21
Start Time:   Wed, 19 Jan 2022 08:54:56 +0000
Labels:       <none>
Annotations:  <none>
Status:       Running
IP:           10.42.0.10
IPs:
  IP:  10.42.0.10
Containers:
  mem-stress:
    Container ID:  containerd://ca4fea45db41b58394ae6e05dd265a72d9ac5cfa2630e296d8cff4dda33416a8
    Image:         polinux/stress
    Image ID:      docker.io/polinux/stress@sha256:b6144f84f9c15dac80deb48d3a646b55c7043ab1d83ea0a697c09097aaad21aa
    Port:          <none>
    Host Port:     <none>
    Command:
      stress
    Args:
      --vm
      1
      --vm-bytes
      15M
      --vm-hang
      1
    State:          Waiting
      Reason:       CrashLoopBackOff
    Last State:     Terminated
      Reason:       OOMKilled
      Exit Code:    1
      Started:      Wed, 19 Jan 2022 09:00:43 +0000
      Finished:     Wed, 19 Jan 2022 09:00:43 +0000
    Ready:          False
    Restart Count:  6
    Limits:
      memory:  10Mi
    Requests:
      memory:     5Mi
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-rhcz7 (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             False 
  ContainersReady   False 
  PodScheduled      True 
Volumes:
  kube-api-access-rhcz7:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   Burstable
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type     Reason     Age                   From               Message
  ----     ------     ----                  ----               -------
  Normal   Scheduled  8m9s                  default-scheduler  Successfully assigned default/elephant to controlplane
  Normal   Pulled     8m7s                  kubelet            Successfully pulled image "polinux/stress" in 1.172580167s
  Normal   Pulled     8m6s                  kubelet            Successfully pulled image "polinux/stress" in 180.697193ms
  Normal   Pulled     7m53s                 kubelet            Successfully pulled image "polinux/stress" in 171.402384ms
  Normal   Pulled     7m30s                 kubelet            Successfully pulled image "polinux/stress" in 260.126705ms
  Normal   Created    7m30s (x4 over 8m7s)  kubelet            Created container mem-stress
  Normal   Started    7m30s (x4 over 8m7s)  kubelet            Started container mem-stress
  Normal   Pulling    6m48s (x5 over 8m8s)  kubelet            Pulling image "polinux/stress"
  Normal   Pulled     6m48s                 kubelet            Successfully pulled image "polinux/stress" in 168.356311ms
  Warning  BackOff    3m1s (x25 over 8m5s)  kubelet            Back-off restarting failed container

04. The status OOMKilled indicates that it is failing because the pod ran out of memory.

Identify the memory limit set on the POD.

05. The elephant pod runs a process that consume 15Mi of memory.

Increase the limit of the elephant pod to 20Mi.

Delete and recreate the pod if required. Do not modify anything other than the required fields.

• Pod Name: elephant
• Image Name: polinux/stress
• Memory Limit: 20Mi

---
apiVersion: v1
kind: Pod
metadata:
  name: elephant
  namespace: default
spec:
  containers:
  - args:
    - --vm
    - "1"
    - --vm-bytes
    - 15M
    - --vm-hang
    - "1"
    command:
    - stress
    image: polinux/stress
    name: mem-stress
    resources:
      limits:
        memory: 20Mi
      requests:
        memory: 5Mi

Create the file elephant.yaml by running command 

kubectl get po elephant -o yaml > elephant.yaml 

and edit the file such as memory limit is set to 20Mi as follows:

kubectl replace -f elephant.yaml --force


controlplane ~ ➜  kubectl replace -f elephant.yaml
Error from server (Conflict): error when replacing "elephant.yaml": Operation cannot be fulfilled on pods "elephant": the object has been modified; please apply your changes to the latest version and try again

controlplane ~ ✖ kubectl replace -f elephant.yaml --force
pod "elephant" deleted
pod/elephant replaced

06. Inspect the status of POD. Make sure it's running

kubectl get po

07. Delete the elephant Pod.

Once deleted, wait for the pod to fully terminate.

kubectl delete pod elephant