关于 K8S pod 对象的健康检查使用描述

前序

什么是 k8s 健康检查？

1. 存活探针 (Liveness Probe)：存活探针用于确定 Pod 是否正在运行。如果存活探针失败，Kubernetes 将终止该容器，并根据容器的重启策略采取相应的操作。存活探针通常用于检测应用程序内部状态，例如检查应用程序是否处于死锁状态或无响应状态。

2. 就绪探针 (Readiness Probe)：就绪探针用于确定 Pod 是否已经准备好接收流量。如果就绪探针失败，该 Pod 将被从 Service 的 Endpoint 中移除，直到就绪探针再次成功为止。就绪探针通常用于确保应用程序已经初始化并且能够处理流量。

3. 启动探针(Startup Probe): 启动探针用于确定应用是否启动完成，如果在 failureThreshold*periodSeconds 周期内未就绪，则会应用进程会被重启。

• HTTP 方式：Kubernetes 可以定期发送 HTTP 请求到容器中的指定端点，并根据返回的状态码和响应内容来判断容器的健康状态。

• TCP 方式：Kubernetes 可以通过尝试建立 TCP 连接来检查容器的健康状态。

• Exec 方式：Kubernetes 可以在容器内部执行特定的命令，并根据命令的返回状态来判断容器的健康状态。

从代码中查看

Pod 定义

// Pod is a collection of containers that can run on a host. This resource is created
// by clients and scheduled onto hosts.
type Pod struct {
	metav1.TypeMeta `json:",inline"`
	// Standard object's metadata.
	// More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
	// +optional
	metav1.ObjectMeta `json:"metadata,omitempty" protobuf:"bytes,1,opt,name=metadata"`

	// Specification of the desired behavior of the pod.
	// More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
	// +optional
	Spec PodSpec `json:"spec,omitempty" protobuf:"bytes,2,opt,name=spec"`

	// Most recently observed status of the pod.
	// This data may not be up to date.
	// Populated by the system.
	// Read-only.
	// More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
	// +optional
	Status PodStatus `json:"status,omitempty" protobuf:"bytes,3,opt,name=status"`
}

PodSpec

// PodSpec is a description of a pod.
type PodSpec struct {
	...
	// List of containers belonging to the pod.
	// Containers cannot currently be added or removed.
	// There must be at least one container in a Pod.
	// Cannot be updated.
	// +patchMergeKey=name
	// +patchStrategy=merge
	Containers []Container `json:"containers" patchStrategy:"merge" patchMergeKey:"name" protobuf:"bytes,2,rep,name=containers"`
	...
}

Container

// A single application container that you want to run within a pod.
type Container struct {
	...
	// Periodic probe of container liveness.
	// Container will be restarted if the probe fails.
	// Cannot be updated.
	// More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
	// +optional
	LivenessProbe *Probe `json:"livenessProbe,omitempty" protobuf:"bytes,10,opt,name=livenessProbe"`
	// Periodic probe of container service readiness.
	// Container will be removed from service endpoints if the probe fails.
	// Cannot be updated.
	// More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
	// +optional
	ReadinessProbe *Probe `json:"readinessProbe,omitempty" protobuf:"bytes,11,opt,name=readinessProbe"`
	// StartupProbe indicates that the Pod has successfully initialized.
	// If specified, no other probes are executed until this completes successfully.
	// If this probe fails, the Pod will be restarted, just as if the livenessProbe failed.
	// This can be used to provide different probe parameters at the beginning of a Pod's lifecycle,
	// when it might take a long time to load data or warm a cache, than during steady-state operation.
	// This cannot be updated.
	// More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
	// +optional
	StartupProbe *Probe `json:"startupProbe,omitempty" protobuf:"bytes,22,opt,name=startupProbe"`
	// Actions that the management system should take in response to container lifecycle events.
	// Cannot be updated.
	// +optional
	...
}

在 web 控制页面上添加健康检查

通过镜像创建应用

查看生成 pod 的 yaml 文件

kind: Pod
apiVersion: v1
metadata:
	...
  name: http-server-gen-6bf89b6b57-bql57
  namespace: ljtian-test
 	...
spec:
  ...
  containers:
    - resources: {}
      name: http-server-gen
      livenessProbe:
        httpGet:
          path: /ping
          port: 8080
          scheme: HTTP
        timeoutSeconds: 1
        periodSeconds: 10
        successThreshold: 1
        failureThreshold: 5
  ...
status:
  phase: Running
  ...

看一下拓扑图

查看 pod 内部日志

结束

资源来源

• k8s gitlab: https://github.com/kubernetes/kubernetes

• 统信有雀平台： https://baijiahao.baidu.com/s?id=1748375472975019664&wfr=spider&for=pc

• k8s 官网： https://kubernetes.io/