4 Kubernetes資源-Pod控制器(2)

4.3 DaemonSet

DaemonSet確保Pod在所有Node節點運行一個副本，當有Node節點添加時會自動在新的節點創建Pod。常用于每個Node上的日志收集、監控、集群存儲管理等。

編寫YAML文件，通過app: tomcat標簽將DaemonSet與Pod資源關聯：

[root@k8smaster43-11 CSDN]# cat daemonset.yaml apiVersion: apps/v1 # API版本 kind: DaemonSet # 資源類型 metadata: name: tomcat-daemons # DS資源名稱 spec: selector: matchLabels: app: tomcat # 關聯Pod標簽template:metadata: name: tomcat-pod # Pod資源名稱labels: app: tomcat # Pod資源標簽 spec: containers: - name: demo-tomcat # Pod容器名稱image: tomcat:8.0 # Pod容器鏡像imagePullPolicy: Never # 容器下載模式 [root@k8smaster43-11 CSDN]#

創建DaemonSet資源：

[root@k8smaster43-11 CSDN]# kubectl create -f daemonset.yaml daemonset.apps/tomcat-daemons created [root@k8smaster43-11 CSDN]# [root@k8smaster43-11 CSDN]# kubectl get ds,pod -o wide --show-labels NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE CONTAINERS IMAGES SELECTOR LABELS daemonset.apps/tomcat-daemons 2 2 2 2 2 <none> 39s demo-tomcat tomcat:8.0 app=tomcat <none>NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES LABELS pod/tomcat-daemons-dqfn4 1/1 Running 0 39s 10.244.2.81 k8sworker43-22 <none> <none> app=tomcat,controller-revision-hash=7f5c98c9cc,pod-template-generation=1 pod/tomcat-daemons-tpz7z 1/1 Running 0 39s 10.244.1.98 k8sworker43-21 <none> <none> app=tomcat,controller-revision-hash=7f5c98c9cc,pod-template-generation=1 [root@k8smaster43-11 CSDN]#

將1臺工作節點從Kubernetes集群中剔除，則DaemonSet的Pod會從該節點刪除：

[root@k8smaster43-11 CSDN]# kubectl delete nodes/k8sworker43-21 node "k8sworker43-21" deleted [root@k8smaster43-11 CSDN]# kubectl get nodes NAME STATUS ROLES AGE VERSION k8smaster43-11 Ready master 107d v1.19.4 k8sworker43-22 Ready <none> 107d v1.19.4 [root@k8smaster43-11 CSDN]# [root@k8smaster43-11 CSDN]# kubectl get ds,pod -o wide --show-labels NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE CONTAINERS IMAGES SELECTOR LABELS daemonset.apps/tomcat-daemons 1 1 1 1 1 <none> 8m19s demo-tomcat tomcat:8.0 app=tomcat <none>NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES LABELS pod/tomcat-daemons-dqfn4 1/1 Running 0 8m19s 10.244.2.81 k8sworker43-22 <none> <none> app=tomcat,controller-revision-hash=7f5c98c9cc,pod-template-generation=1 [root@k8smaster43-11 CSDN]#

將1臺工作節點加入Kubernetes集群中，則DaemonSet會自動從該節點啟動Pod：

# 在工作節點執行kubeadm join命令加入集群 [root@k8sworker43-21 ~]# kubeadm join 192.168.43.11:6443 --token d1ncs0.we7r79976ndaf3k4 --discovery-token-ca-cert-hash sha256:28d33e6003840de19700fbba569f32557c57841ff94516720eadc072e4b3a099 [preflight] Running pre-flight checks [preflight] Reading configuration from the cluster... [preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml' [kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml" [kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env" [kubelet-start] Starting the kubelet [kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...This node has joined the cluster: * Certificate signing request was sent to apiserver and a response was received. * The Kubelet was informed of the new secure connection details.Run 'kubectl get nodes' on the control-plane to see this node join the cluster. [root@k8sworker43-21 ~]# #在Master節點查看DaemonSet資源情況 [root@k8smaster43-11 CSDN]# kubectl get nodes NAME STATUS ROLES AGE VERSION k8smaster43-11 Ready master 107d v1.19.4 k8sworker43-21 Ready <none> 12s v1.19.4 k8sworker43-22 Ready <none> 107d v1.19.4 [root@k8smaster43-11 CSDN]# [root@k8smaster43-11 CSDN]# kubectl get ds,pod -o wide --show-labels NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE CONTAINERS IMAGES SELECTOR LABELS daemonset.apps/tomcat-daemons 2 2 2 2 2 <none> 20m demo-tomcat tomcat:8.0 app=tomcat <none>NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES LABELS pod/tomcat-daemons-cvxrb 1/1 Running 0 10s 10.244.1.2 k8sworker43-21 <none> <none> app=tomcat,controller-revision-hash=7f5c98c9cc,pod-template-generation=1 pod/tomcat-daemons-dqfn4 1/1 Running 0 20m 10.244.2.81 k8sworker43-22 <none> <none> app=tomcat,controller-revision-hash=7f5c98c9cc,pod-template-generation=1 [root@k8smaster43-11 CSDN]#

刪除DaemonSet和對應Pod的資源：

[root@k8smaster43-11 CSDN]# kubectl delete -f daemonset.yaml daemonset.apps "tomcat-daemons" deleted [root@k8smaster43-11 CSDN]#

4.4 Job/CronJob

Job負責批處理任務，即僅執行一次的任務，它保證批處理的一個或多個Pod成功結束。

編寫YAML文件，設置任務的執行次數 completions為4次、同時執行的任務數量parallelism為2個，因為任務是執行完就結束所以Pod的重啟策略restartPolicy:為Never：

[root@k8smaster43-11 CSDN]# cat job.yaml apiVersion: batch/v1 # API版本 kind: Job # 資源類型 metadata: name: perl-job # Job資源名稱 spec:completions: 4 # Job執行次數parallelism: 2 # Job并發數量template: metadata: name: perl-pod # Pod資源標簽spec: containers: - name: perl # Pod容器名稱image: perl # Pod容器鏡像command: ["perl", "-Mbignum=bpi", "-wle", "print bpi(2000)"]restartPolicy: Never # Pod重啟策略 [root@k8smaster43-11 CSDN]#

創建Job資源并查看任務執行狀態，Pod為Running表示正在執行、Completed表示執行結束：

[root@k8smaster43-11 CSDN]# kubectl create -f job.yaml job.batch/perl-job created [root@k8smaster43-11 CSDN]# kubectl get job,pod -o wide NAME COMPLETIONS DURATION AGE CONTAINERS IMAGES SELECTOR job.batch/perl-job 0/4 19s 19s perl perl controller-uid=517a4293-107a-4c05-8480-611b63dc8de5NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES pod/perl-job-ggspc 1/1 Running 0 19s 10.244.2.86 k8sworker43-22 <none> <none> pod/perl-job-p796m 1/1 Running 0 19s 10.244.2.87 k8sworker43-22 <none> <none># 有2個任務同時執行，任務執行結束Pod狀態變為Completed [root@k8smaster43-11 CSDN]# kubectl get job,pod -o wide NAME COMPLETIONS DURATION AGE CONTAINERS IMAGES SELECTOR job.batch/perl-job 2/4 30s 30s perl perl controller-uid=517a4293-107a-4c05-8480-611b63dc8de5NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES pod/perl-job-ggspc 0/1 Completed 0 30s 10.244.2.86 k8sworker43-22 <none> <none> pod/perl-job-gkrsf 1/1 Running 0 2s 10.244.2.89 k8sworker43-22 <none> <none> pod/perl-job-p796m 0/1 Completed 0 30s 10.244.2.87 k8sworker43-22 <none> <none> pod/perl-job-slr82 1/1 Running 0 4s 10.244.2.88 k8sworker43-22 <none> <none>

刪除Job和對應Pod的資源：

[root@k8smaster43-11 CSDN]# kubectl delete -f job.yaml job.batch "perl-job" deleted [root@k8smaster43-11 CSDN]#

CronJob負責在給定時間調度Job，或者按照周期運行Job。常用于定時任務腳本、數據庫備份、定時郵件發送等。

編寫YAML文件，通過schedule字段設置定時任務的時間間隔：

[root@k8smaster43-11 CSDN]# cat cronjob.yaml apiVersion: batch/v1beta1 # API版本 kind: CronJob # 資源類型 metadata: name: busybox-cronjob # CronJob資源名稱 spec:schedule: "*/1 * * * *" # 批處理時間間隔60sjobTemplate: spec: completions: 1 # Job執行次數parallelism: 1 # Job并發數量template: metadata: app: busybox # Pod資源標簽spec: containers: - name: busybox # Pod容器名稱image: busybox # Pod容器鏡像command: ["sh", "-c", "date; echo Hello from the kubernetes cluster"]restartPolicy: Never # Pod重啟策略 [root@k8smaster43-11 CSDN]#

創建CronJob資源并觀察執行過程，通過successfulJobsHistoryLimit字段可以設置需要保留的成功完成任務的Job個數，超過該數值的Job會被刪除：

[root@k8smaster43-11 CSDN]# kubectl get cronjob,job,pod -o wide NAME SCHEDULE SUSPEND ACTIVE LAST SCHEDULE AGE CONTAINERS IMAGES SELECTOR cronjob.batch/busybox-cronjob */1 * * * * False 0 31s 9m21s busybox busybox <none>NAME COMPLETIONS DURATION AGE CONTAINERS IMAGES SELECTOR job.batch/busybox-cronjob-1658563620 1/1 18s 2m30s busybox busybox controller-uid=87d090c6-bbe4-48ca-8849-fc3a941d7bf4 job.batch/busybox-cronjob-1658563680 1/1 19s 90s busybox busybox controller-uid=673942e5-18fc-445e-b203-a264d271d5cb job.batch/busybox-cronjob-1658563740 1/1 17s 29s busybox busybox controller-uid=c54ceea2-93e8-4b7e-83a3-b40e29113005NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES pod/busybox-cronjob-1658563620-7d88g 0/1 Completed 0 2m30s 10.244.2.93 k8sworker43-22 <none> <none> pod/busybox-cronjob-1658563680-528dd 0/1 Completed 0 90s 10.244.1.10 k8sworker43-21 <none> <none> pod/busybox-cronjob-1658563740-h25ff 0/1 Completed 0 29s 10.244.2.94 k8sworker43-22 <none> <none> [root@k8smaster43-11 CSDN]#

刪除CornJob和對應Job、Pod的資源：

[root@k8smaster43-11 CSDN]# kubectl delete -f cronjob.yaml cronjob.batch "busybox-cronjob" deleted [root@k8smaster43-11 CSDN]#

4.5 StatefulSet

StatefulSet負責有狀態服務問題，為每個Pod提供唯一的標識{StatefulSetName}-{0-N}，保證部署和擴容的有序性，而其他控制器生成的Pod標識符存在隨機值。

應用場景（案例在后續Service和PV/PVC部分）：

• 穩定持久化存儲，Pod重新調度后還能訪問到相同的持久化數據，基于PVC實現的為每個Pod匹配一個PVC；
• 穩定的網絡標志，Pod重新調度后其PodName和HostName不變，基于Headless Service實現的可以在容器內部ping PodName.HeadlessServiceName,而其他類型的Service只能ping ServiceName；
• 有序部署有序擴展，在部署和擴展的時候要依據定義的順序依次運行，在下一個Pod運行之前所有前序Pod必須都是Running和Ready狀態，基于init container實現；
• 有序收縮有序刪除。

總結

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