k8s学习-DaemonSet和Job

1.1DaemonSet是什么

Deployment部署的副本Pod会分布在各个Node上，每个Node都可能运行好几个副本。DaemonSet的不同之处在于：每个Node上最多只能运行⼀个副本。DaemonSet的典型应用场景有：
（1）在集群的每个节点上运⾏存储Daemon，比如glusterd或ceph。
（2）在每个节点上运行日志收集Daemon，比如flunentd或logstash。
（3）在每个节点上运行监控Daemon，比如PrometheusNodeExporter或collectd。

其实Kubernetes自己就在用DaemonSet运行系统组件。执行如下命令，如下所示。

kubectl get daemonset --namespace=kube-systemkubectl get daemonset --namespace=kube-flannel

[root@k8s-master ~]# kubectl get daemonset --namespace=kube-flannelNAMEDESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGEkube-flannel-ds 3 3 3 33 <none>10d[root@k8s-master ~]# kubectl get daemonset --namespace=kube-flannelNAMEDESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGEkube-flannel-ds 3 3 3 33 <none>10d

DaemonSet kube-flannel-ds和kube-proxy分别负责在每个节点上运⾏flannel和kube-proxy组件，在通过查看Pod副本，看看各个节点的分布情况：

kubectl get pod --namespace=kube-system -o wide

[root@k8s-master ~]# kubectl get pod --namespace=kube-system -o wideNAME READY STATUSRESTARTS AGE IPNODE NOMINATED NODE READINESS GATEScoredns-7ff77c879f-ltqn4 1/1 Running 210d 10.244.0.8k8s-master <none> <none>coredns-7ff77c879f-xb6qm 1/1 Running 210d 10.244.0.9k8s-master <none> <none>etcd-k8s-master1/1 Running 210d 192.168.200.128 k8s-master <none> <none>kube-apiserver-k8s-master1/1 Running 210d 192.168.200.128 k8s-master <none> <none>kube-controller-manager-k8s-master 1/1 Running 210d 192.168.200.128 k8s-master <none> <none>kube-proxy-dcprp 1/1 Running 210d 192.168.200.128 k8s-master <none> <none>kube-proxy-nklr5 1/1 Running 210d 192.168.200.129 k8s-node1<none> <none>kube-proxy-slslc 1/1 Running 410d 192.168.200.130 k8s-node2<none> <none>kube-scheduler-k8s-master1/1 Running 210d 192.168.200.128 k8s-master <none> <none>metrics-server-7f6b85b597-k6b261/1 Running 210d 10.244.1.29 k8s-node1<none> <none>

1.2 DaemonSet的创建和运行

本小节以Prometheus Node Exporter为例演示用户如何运行自己的DaemonSet。Prometheus 是 流行的系统监控方案 ， Node Exporter 是Prometheus的agent，以Daemon的形式运行在每个被监控节点
上。
vi node-exporter.yaml

apiVersion: apps/v1kind: DaemonSetmetadata:name: node-exporter-daemonsetnamespace: agentspec:selector:matchLabels:app: prometheustemplate:metadata:labels:app: prometheusspec:hostNetwork: truecontainers:- name: node-exporterimage: prom/node-exporterimagePullPolicy: IfNotPresentcommand:- /bin/node_exporter- --path.procfs- /host/proc- --path.sysfs- /host/sys---collector.filesystem.ignored-mount-points- ^/(sys|proc|dev|host|etc)($|/)volumeMounts:- name: procmountPath: /host/proc- name: sysmountPath: /host/sys- name: rootmountPath: /rootfsvolumes:- name: prochostPath:path: /proc- name: syshostPath:path: /sys- name: roothostPath:path: /

先创建个命名空间

kubectl create namespace agent

通过kubectl创建资源：

kubectl apply -f node-exporter.yaml

然后，通过kubectl查看Pod分布情况：

[root@k8s-master ~]# kubectl get pod --namespace=agent -o wideNAMEREADY STATUSRESTARTS AGE IPNODENOMINATED NODE READINESS GATESnode-exporter-daemonset-5rrq4 1/1 Running 144h 192.168.200.129 k8s-node1 <none> <none>node-exporter-daemonset-hjkzs 1/1 Running 144h 192.168.200.130 k8s-node2 <none> <none>

2.1 Job

容器按照持续运行的时间可分为两类：服务类容器和工作类容器。
服务类容器通常持续提供服务，需要⼀直运行，比如HTTPServer、Daemon等。工作类容器则是⼀次性任务，比如批处理程序，完成后容器就退出。
Kubernetes的Deployment、ReplicaSet和DaemonSet都用于管理服务类容器；
对于工作类容器，我们使用Job。先看⼀个简单的Job配置文件件myjob.yml。

vi myjob.yml

apiVersion: batch/v1kind: Jobmetadata:name: myjobnamespace: jobsspec:template:metadata:labels:app: myjobspec:containers:- name: hello-jobimage: busyboximagePullPolicy: IfNotPresentcommand: ["echo", "hellok8s job!"]restartPolicy: Never

kubectl apply -f myjob.yml

通过查看Job运行情况可以知道，其运行结束就结束了，如下图所示，变成了Completed状态。

kubectl get pod -n jobs

[root@k8s-master ~]# kubectl get pod -n jobsNAMEREADY STATUSRESTARTS AGEmyjob-krgdh 0/1 Completed 044h

还可以通过查看Log看看这个Job留下的足迹：

kubectl logs myjob-krgdh -n jobs #查看日志kubectl describe pods/myjob-krgdh --namespace jobs #查看job描述

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[root@k8s-master ~]# kubectl logs myjob-krgdh -n jobshellok8s job![root@k8s-master ~]# kubectl describe pods/myjob-krgdh --namespace jobsName: myjob-krgdhNamespace:jobsPriority: 0Node: k8s-node2/192.168.200.130Start Time: Sat, 27 Jan 2024 16:53:58 +0800Labels: app=myjobcontroller-uid=1a312a0b-b6eb-4219-958f-801edc224608job-name=myjobAnnotations:<none>Status: SucceededIP: 10.244.2.14IPs:IP: 10.244.2.14Controlled By:Job/myjobContainers:hello-job:Container ID:docker://0403ccea759585e45f39431bf3958a169211210ef948a0b7c1d4be1ed411e272Image: busyboxImage ID:docker-pullable://busybox@sha256:5acba83a746c7608ed544dc1533b87c737a0b0fb730301639a0179f9344b1678Port:<none>Host Port: <none>Command:echohellok8s job!State:TerminatedReason: CompletedExit Code:0Started:Sat, 27 Jan 2024 16:53:59 +0800Finished: Sat, 27 Jan 2024 16:53:59 +0800Ready:FalseRestart Count:0Environment:<none>Mounts:/var/run/secrets/kubernetes.io/serviceaccount from default-token-vz4wm (ro)Conditions:TypeStatusInitialized TrueReady FalseContainersReady FalsePodScheduledTrueVolumes:default-token-vz4wm:Type:Secret (a volume populated by a Secret)SecretName:default-token-vz4wmOptional:falseQoS Class: BestEffortNode-Selectors:<none>Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300sEvents:<none>

2.2 并行Job

如果希望能够同时并行运行多个Pod以提高Job的执行效率，Job提供了一个贴心的配置：parallesim。例如下面的配置，我们将上面的小Job改为并行运行的Pod数量设置为3。
修改 myjob.yml

apiVersion: batch/v1kind: Jobmetadata:name: testjobspec:parallelism: 3template:metadata:labels:app: testjobspec:containers:- name: hello-jobimage: busyboximagePullPolicy: IfNotPresentcommand: ["echo", "hellok8s job!"]restartPolicy: Never

kubectl get pod -o wide -n default

可以看出，Job一共启动了3个Pod，都是同时结束的（可以看到三个Pod的AGE都是相同的）。

[root@k8s-master ~]# kubectl get pod -o wide -n defaultNAMEREADY STATUSRESTARTS AGE IP NODENOMINATED NODE READINESS GATEStestjob-jmlzm 0/1 Completed 044h 10.244.2.18k8s-node2 <none> <none>testjob-r62f4 0/1 Completed 044h 10.244.2.17k8s-node2 <none> <none>testjob-vg7c6 0/1 Completed 044h 10.244.2.16k8s-node2 <none> <none>

2.3 定时Job

Linux中有cron程序定时执行任务，Kubernetes的CronJob提供了类似的功能，可以定时执行Job。
vi hello-cron-job.yml

apiVersion: batch/v1beta1kind: CronJobmetadata:name: hello-cron-jobnamespace: jobsspec:schedule: "*/1 * * * *"jobTemplate:spec:template:spec:containers:- name: hello-cron-jobimage: busyboximagePullPolicy: IfNotPresentcommand: ["echo", "hello edison's k8s cron job!"]restartPolicy: OnFailure

上面加粗的配置是CronJob的独有配置，需要注意的是schedule，它的格式和Linux Cron一样，这里的”*/1 * * * *”代表每一分钟启动执行一次。对于CronJob，它需要的是jobTemplate来定义Job的模板。

kubectl get cronjob -n jobs

[root@k8s-master ~]# kubectl get cronjob -n jobsNAME SCHEDULESUSPEND ACTIVE LAST SCHEDULE AGEhello-cron-job */1 * * * * False 043h 43h

查看job

可以看到，在过去的三分钟里，每一分钟都启动了一个Pod，符合预期。

kubectl get jobs -n jobs

[root@k8s-master ~]# kubectl get jobs -n jobsNAMECOMPLETIONS DURATION AGEhello-cron-job-1706350440 1/1 1s 43hhello-cron-job-1706350500 1/1 1s 43hhello-cron-job-1706350560 1/1 1s 43h