phpwind 企业网站精准营销的概念
测试容器并不是什么都没有的容器，只是它没有我们期望的常驻进程。我们常用它来做一些测试。
举个例子，在《研发工程师玩转Kubernetes——自动扩缩容》中我们使用本地wrk进行了压力测试。如果我们希望进入容器手工调用wrk，该怎么做呢？
错误的案例
虽然下面这个清单文件的镜像中包含了wrk程序，但是它没有启动一个常驻进程。导致运行这个Pod一直会报错“Back-off restarting failed container”，Reason是CrashLoopBackOff。
apiVersion: v1
kind: Pod
metadata:name: wrklabels:name: wrk
spec:containers:- name: wrk-containerimage: localhost:32000/wrk:v1
kubectl describe pod wrk
Name: wrk
Namespace: default
Priority: 0
Service Account: default
Node: fangliang-virtual-machine/192.168.137.248
Start Time: Mon, 29 May 2023 14:30:37 +0800
Labels: name=wrk
Annotations: cni.projectcalico.org/containerID: 75a18bfd3f3d83dd14b7bc9655343842d9bac20a4c52a7ee75932013be395e01cni.projectcalico.org/podIP: 10.1.62.178/32cni.projectcalico.org/podIPs: 10.1.62.178/32
Status: Running
IP: 10.1.62.178
IPs:IP: 10.1.62.178
Containers:wrk-container:Container ID: containerd://80d5186f701de4ccd861dc84078290250f3452a90ed226cb246a4f6b9aab5ef6Image: localhost:32000/wrk:v1Image ID: localhost:32000/wrk@sha256:3548119fa498e871ac75ab3cefb901bf5a069349dc4b1b92afab8db4653f6b25Port: <none>Host Port: <none>State: WaitingReason: CrashLoopBackOffLast State: TerminatedReason: CompletedExit Code: 0Started: Mon, 29 May 2023 14:31:17 +0800Finished: Mon, 29 May 2023 14:31:17 +0800Ready: FalseRestart Count: 3Environment: <none>Mounts:/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-ld6j6 (ro)
Conditions:Type StatusInitialized True Ready False ContainersReady False PodScheduled True
Volumes:kube-api-access-ld6j6:Type: Projected (a volume that contains injected data from multiple sources)TokenExpirationSeconds: 3607ConfigMapName: kube-root-ca.crtConfigMapOptional: <nil>DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300snode.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:Type Reason Age From Message---- ------ ---- ---- -------Normal Scheduled 54s default-scheduler Successfully assigned default/wrk to fangliang-virtual-machineNormal Pulled 14s (x4 over 53s) kubelet Container image "localhost:32000/wrk:v1" already present on machineNormal Created 14s (x4 over 53s) kubelet Created container wrk-containerNormal Started 14s (x4 over 53s) kubelet Started container wrk-containerWarning BackOff 2s (x6 over 52s) kubelet Back-off restarting failed container wrk-container in pod wrk_default(588fb4f3-d649-4570-b64c-a4eff748417d)
正确的案例
我们只要启动一个常驻进程就可以解决这个问题。
在linux系统中，/dev/null是一个非常特殊的文件，它会抛弃所有写入其中的数据。于是我们持续查看这个文件的写入，就可以制造一个常驻进程，而且没有其他额外的影响。
command: [“/bin/bash”, “-ce”, “tail -f /dev/null”]
即把清单文件改成如下
apiVersion: v1
kind: Pod
metadata:name: wrklabels:name: wrk
spec:containers:- name: wrk-containerimage: localhost:32000/wrk:v1command: ["/bin/bash", "-ce", "tail -f /dev/null"]
测试
创建Pod
kubectl create -f wrk_pod.yaml
pod/wrk created
登录容器
kubectl exec wrk -c wrk-container -it /bin/bash
执行指令
wrk -t10 -c10 -d10 http://192.168.137.248:30000
可见，我们已经可以在这个测试容器中执行我们想执行的指令了。
参考资料
- https://blog.csdn.net/yztezhl/article/details/125421316
- https://linuxhint.com/what_is_dev_null/