DaemonSet典型应用
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：
·在集群的每个节点上运行存储Daemon，比如glusterd或ceph。
·在每个节点上运行日志收集Daemon，比如flunentd或logstash。
·在每个节点上运行监控Daemon，比如Prometheus Node ExPorter或collectd。
其实Kubernetes自己就在用DaemonSet运行系统组件。
主机查看系统的daemonset组件：
[root@master ~]# kubectl get daemonsets.apps -n kube-system NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE kube-flannel-ds-amd64 3 3 3 3 3 <none> 7d1h kube-flannel-ds-arm 0 0 0 0 0 <none> 7d1h kube-flannel-ds-arm64 0 0 0 0 0 <none> 7d1h kube-flannel-ds-ppc64le 0 0 0 0 0 <none> 7d1h kube-flannel-ds-s390x 0 0 0 0 0 <none> 7d1h kube-proxy 3 3 3 3 3 beta.kubernetes.io/os=linux 7d1h
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。
master主机编写YAML配置文件，然后通过文件创建DaemonSet，最后查看DaemonSet的状态：
案例：
[root@master ~]# cat busybox.yml apiVersion: apps/v1 kind: DaemonSet metadata: name: busybox-daemonset spec: selector: matchLabels: app: busybox template: metadata: labels: app: busybox spec: containers: - name : test image: busybox command: - sh - -c - while true;do echo "test";sleep 10;done;
kubectl apply -f busybox.yml
查看：
[root@master ~]# kubectl get daemonsets.apps NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE busybox-daemonset 2 2 2 2 2 <none> 48m
[root@master ~]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES busybox-daemonset-lcz4g 1/1 Running 0 49m 10.244.1.15 node1 <none> <none> busybox-daemonset-mz82h 1/1 Running 0 49m 10.244.2.20 node2 <none> <none>
[root@master ~]# kubectl logs -f busybox-daemonset-lcz4g
案例：部署exporter
[root@master caoyi]# cat node-exporter.yml apiVersion: apps/v1 kind: DaemonSet metadata: name: exporter-daemonset spec: selector: matchLabels: app: node-exporter template: metadata: labels: app: node-exporter spec: hostNatwork: true spec: containers: - name : node-exporter image: prom/node-exporter command: - /bin/node_exporter - --path.procfs - /host/proc - --path.sysfs - /host/sys - --collector.filesystem.ignored-mount-points - ^/(sys|proc|dev|host|etc|rootfs/var/lib/docker/containers|rootfs/var/lib/docker/overlay2|rootfs/run/docker/netns|rootfs/var/lib/docker/devicemapper|rootfs/var/lib/docker/aufs)($$|/) volumeMounts: - name: proc mountPath: /host/proc - name: sys mountPath: /host/sys - name: root mountPath: /rootfs volumes: - name: proc hostPath: path: /proc - name: sys hostPath: path: /sys - name: root hostPath: path: /
[root@master caoyi]# kubectl apply -f node-exporter.yml
查看：
[root@master caoyi]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES busybox-daemonset-lcz4g 1/1 Running 0 55m 10.244.1.15 node1 <none> <none> busybox-daemonset-mz82h 1/1 Running 0 55m 10.244.2.20 node2 <none> <none> exporter-daemonset-7qw72 1/1 Running 0 118s 10.244.1.16 node1 <none> <none> exporter-daemonset-pvzjv 1/1 Running 0 118s 10.244.2.21 node2 <none> <none>
job
容器按照持续运行的时间分为两类：服务类容器和工作类容器
服务类容器通常持续提供了服务，需要一直运行，比如http server，daemon等。工作类容器则是一次性任务，比如批处理程序，完成后容器就退出了。
kubernetes的deployment、replicaSet 和 DaemonSet都用于管理服务类容器：对于工作类容器，我们用job.
案例：容器不重启
模拟job正确的
[root@master caoyi]# cat myjob.yml apiVersion: batch/v1 kind: Job ##指明当前资源的类型为Job metadata: name: myjob spec: template: metadata: name: myjob spec: containers: - name: hello image: busybox command: ["echo","hello"] restartPolicy: Never ##restartPolicy 指定什么情况下需要重启容器，对于job，只能设置为never或者ONFailure，对于其他的controller（比如deployment）可以设置为Always
[root@master caoyi]# kubectl get pod -o wide myjob-6ll52 0/1 Completed 0 23m 10.244.1.17 node1 <none> <none>
模拟失败的job
在command 处修改一个错误的命令，如果输出一个错误的不存在的命令，启动的时候起不起来，隔一段时间会重新创建一个，直到启动了才会停止
当第一个pod启动时，容器失败退出，由于设置restartpolicy：Never，此容器不会被重启，但job desired的pod是目前successful为0，达不到要求。所以会启动新的pod知道successful为1。为了终止这个行为，只能删除job。
案例：容器重启
[root@master caoyi]# cat myjob.yml apiVersion: batch/v1 kind: Job metadata: name: myjob spec: template: metadata: name: myjob spec: containers: - name: hello image: busybox command: ["xxxxx","hello"] restartPolicy: OnFailure ##只有在运行成功才会停止进行重启，只要有错误，它会一直进行重启
查看
[root@master caoyi]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES busybox-daemonset-lcz4g 1/1 Running 0 109m 10.244.1.15 node1 <none> <none> busybox-daemonset-mz82h 1/1 Running 0 109m 10.244.2.20 node2 <none> <none> exporter-daemonset-7qw72 1/1 Running 0 56m 10.244.1.16 node1 <none> <none> exporter-daemonset-pvzjv 1/1 Running 0 56m 10.244.2.21 node2 <none> <none> myjob-tk5br 0/1 RunContainerError 2 50s 10.244.1.18 node1 <none> <none> [root@master caoyi]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES busybox-daemonset-lcz4g 1/1 Running 0 111m 10.244.1.15 node1 <none> <none> busybox-daemonset-mz82h 1/1 Running 0 111m 10.244.2.20 node2 <none> <none> exporter-daemonset-7qw72 1/1 Running 0 57m 10.244.1.16 node1 <none> <none> exporter-daemonset-pvzjv 1/1 Running 0 57m 10.244.2.21 node2 <none> <none> myjob-tk5br 0/1 CrashLoopBackOff 4 2m19s 10.244.1.18 node1 <none> <none>
同时执行多个Job
[root@master caoyi]# cat myjob.yml apiVersion: batch/v1 kind: Job metadata: name: myjob spec: completions: 6 ##每次运行两个pod，直到共运行6个pod成功完成 parallelism: 2 template: metadata: name: myjob spec: containers: - name: hello image: busybox command: ["echo","hello"] restartPolicy: OnFailure
[root@master caoyi]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES myjob-98wf9 0/1 Completed 0 98s 10.244.2.25 node2 <none> <none> myjob-cvq4n 0/1 Completed 0 103s 10.244.2.22 node2 <none> <none> myjob-hgvkb 0/1 Completed 0 101s 10.244.2.23 node2 <none> <none> myjob-kvf4g 0/1 Completed 0 96s 10.244.2.27 node2 <none> <none> myjob-lzckc 0/1 Completed 0 103s 10.244.1.19 node1 <none> <none> myjob-mvv4k 0/1 Completed 0 99s 10.244.1.20 node1 <none> <none>
定时执行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，
[root@master caoyi]# cat cronjob.yml apiVersion: batch/v1beta1 kind: CronJob metadata: name: cronjob spec: schedule: "*/1 * * * *" jobTemplate: spec: template: spec: containers: - name: hello image: busybox command: ["echo","hello"] restartPolicy: OnFailure
[root@master caoyi]# kubectl apply -f cronjob.yml
查看
[root@master caoyi]# kubectl get pod -o wide No resources found in default namespace. 当前是没有的 1分钟以后 [root@master caoyi]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES cronjob-1594910220-ddfvc 0/1 Completed 0 16s 10.244.1.23 node1 <none> <none> 两分钟后 [root@master caoyi]# kubectl get pod -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES cronjob-1594910280-2fqdr 0/1 Completed 0 2m44s 10.244.1.25 node1 <none> <none> cronjob-1594910340-msnxz 0/1 Completed 0 104s 10.244.1.27 node1 <none> <none>
