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google-kubernetes-engine - Liveness Probe，Readiness Probe 未在预期持续时间内调用

问题描述

在 GKE 上，我尝试使用 readiness probe/ liveness probe ，并使用监控https://cloud.google.com/monitoring/alerts/using-alerting-ui发布警报

作为测试，我创建了一个具有就绪探针/活性探针的 pod。正如我所料，探针检查每次都失败。

apiVersion: v1
kind: Pod
metadata:
  labels:
    test: liveness
  name: liveness-http
spec:
  containers:
  - name: liveness
    image: k8s.gcr.io/liveness
    args:
    - /server
    readinessProbe:
      httpGet:
        path: /healthz
        port: 8080
        httpHeaders:
        - name: X-Custom-Header
          value: Awesome
      initialDelaySeconds: 0
      periodSeconds: 10      
      timeoutSeconds: 10
      successThreshold: 1
      failureThreshold: 3
    livenessProbe:
      httpGet:
        path: /healthz
        port: 8080
        httpHeaders:
        - name: X-Custom-Header
          value: Awesome
      initialDelaySeconds: 20
      periodSeconds: 60
      timeoutSeconds: 30      
      successThreshold: 1
      failureThreshold: 3

并检查 GCP 日志，两个错误日志都首先基于 periodSeconds 显示。

就绪探测：每 10 秒

2021-02-21 13:26:30.000 JST 就绪探测失败：HTTP 探测失败，状态码：500

2021-02-21 13:26:40.000 JST 就绪探测失败：HTTP 探测失败，状态码：500

活度探测：每 1 分钟

2021-02-21 13:25:40.000 JST Liveness 探测失败：HTTP 探测失败，状态码：500

2021-02-21 13:26:40.000 JST Liveness 探测失败：HTTP 探测失败，状态码：500

但是，在运行这个 pod 几分钟后

$ kubectl get event
LAST SEEN   TYPE      REASON      OBJECT              MESSAGE
30m         Normal    Pulling     pod/liveness-http   Pulling image "k8s.gcr.io/liveness"
25m         Warning   Unhealthy   pod/liveness-http   Readiness probe failed: HTTP probe failed with statuscode: 500
20m         Warning   BackOff     pod/liveness-http   Back-off restarting failed container
20m         Normal    Scheduled   pod/liveness-http   Successfully assigned default/liveness-http to gke-cluster-default-pool-8bc9c75c-rfgc
17m         Normal    Pulling     pod/liveness-http   Pulling image "k8s.gcr.io/liveness"
17m         Normal    Pulled      pod/liveness-http   Successfully pulled image "k8s.gcr.io/liveness"
17m         Normal    Created     pod/liveness-http   Created container liveness
20m         Normal    Started     pod/liveness-http   Started container liveness
4m59s       Warning   Unhealthy   pod/liveness-http   Readiness probe failed: HTTP probe failed with statuscode: 500
17m         Warning   Unhealthy   pod/liveness-http   Liveness probe failed: HTTP probe failed with statuscode: 500
17m         Normal    Killing     pod/liveness-http   Container liveness failed liveness probe, will be restarted

在我的计划中，我将创建警报策略，其条件类似于

但是如果探测检查没有像我预期的那样调用，那么这些策略就不起作用；即使 pod 没有运行，警报也已修复

为什么 Liveness 探针没有运行，而 Readiness 探针的间隔发生了变化？

注意：如果有其他好的警报策略来检查 pod 的活跃度，我不会在意这种行为。如果有人能建议我哪种警报策略最适合检查 pod，我将不胜感激。

标签： google-kubernetes-enginegoogle-cloud-monitoringreadinessprobelivenessprobe

解决方案

背景

在Configure Liveness、Readiness 和 Startup Probes文档中，您可以找到以下信息：

kubelet 用于liveness probes知道何时重新启动容器。例如，活跃度探针可以捕获死锁，即应用程序正在运行，但无法取得进展。尽管存在错误，但在这种状态下重新启动容器有助于使应用程序更可用。

kubelet 用于readiness probes了解容器何时准备好开始接受流量。当 Pod 的所有容器都准备好时，就认为 Pod 准备好了。此信号的一种用途是控制哪些 Pod 用作服务的后端。当 Pod 未准备好时，它会从服务负载均衡器中移除。

由于GKEmaster 由 google 管理，您将找不到kubelet使用的日志CLI（您可能会尝试使用Stackdriver）。我已经在Kubeadm集群上对其进行了测试并将verbosity级别设置为8.

当您使用时，$ kubectl get events您只能从最后一小时获得事件（它可以在 Kubernetes 设置中更改 -Kubeadm但我认为它不能更改，GKE因为 master 由谷歌管理。）

$ kubectl get events
LAST SEEN   TYPE      REASON                    OBJECT              MESSAGE
37m         Normal    Starting                  node/kubeadm        Starting kubelet.
...
33m         Normal    Scheduled                 pod/liveness-http   Successfully assigned default/liveness-http to kubeadm
33m         Normal    Pulling                   pod/liveness-http   Pulling image "k8s.gcr.io/liveness"
33m         Normal    Pulled                    pod/liveness-http   Successfully pulled image "k8s.gcr.io/liveness" in 893.953679ms
33m         Normal    Created                   pod/liveness-http   Created container liveness
33m         Normal    Started                   pod/liveness-http   Started container liveness
3m12s       Warning   Unhealthy                 pod/liveness-http   Readiness probe failed: HTTP probe failed with statuscode: 500
30m         Warning   Unhealthy                 pod/liveness-http   Liveness probe failed: HTTP probe failed with statuscode: 500
8m17s       Warning   BackOff                   pod/liveness-http   Back-off restarting failed container

之后再次执行相同的命令~1 hour。

$ kubectl get events
LAST SEEN   TYPE      REASON      OBJECT              MESSAGE
33s         Normal    Pulling     pod/liveness-http   Pulling image "k8s.gcr.io/liveness"
5m40s       Warning   Unhealthy   pod/liveness-http   Readiness probe failed: HTTP probe failed with statuscode: 500
15m         Warning   BackOff     pod/liveness-http   Back-off restarting failed container

测试

检查每 10 秒执行一次，Readiness Probe持续时间超过一小时。

Mar 09 14:48:34 kubeadm kubelet[3855]: I0309 14:48:34.222085    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 14:48:44 kubeadm kubelet[3855]: I0309 14:48:44.221782    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 14:48:54 kubeadm kubelet[3855]: I0309 14:48:54.221828    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
...
Mar 09 15:01:34 kubeadm kubelet[3855]: I0309 15:01:34.222491    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4
562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 15:01:44 kubeadm kubelet[3855]: I0309 15:01:44.221877    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 15:01:54 kubeadm kubelet[3855]: I0309 15:01:54.221976    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
...
Mar 09 15:10:14 kubeadm kubelet[3855]: I0309 15:10:14.222163    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 15:10:24 kubeadm kubelet[3855]: I0309 15:10:24.221744    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 15:10:34 kubeadm kubelet[3855]: I0309 15:10:34.223877    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
...
Mar 09 16:04:14 kubeadm kubelet[3855]: I0309 16:04:14.222853    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 16:04:24 kubeadm kubelet[3855]: I0309 16:04:24.222531    3855 prober.go:117] Readiness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500

此外，还有Liveness probe条目。

Mar 09 16:12:58 kubeadm kubelet[3855]: I0309 16:12:58.462878    3855 prober.go:117] Liveness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 16:13:58 kubeadm kubelet[3855]: I0309 16:13:58.462906    3855 prober.go:117] Liveness probe for "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a):liveness" failed (failure): HTTP probe failed with statuscode: 500
Mar 09 16:14:58 kubeadm kubelet[3855]: I0309 16:14:58.465470    3855 kuberuntime_manager.go:656] Container "liveness" ({"docker" "95567f85708ffac8b34b6c6f2bdb4
9d8eb57e7704b7b416083c7f296dd40cd0b"}) of pod liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a): Container liveness failed liveness probe, will be restarted
Mar 09 16:14:58 kubeadm kubelet[3855]: I0309 16:14:58.465587    3855 kuberuntime_manager.go:712] Killing unwanted container "liveness"(id={"docker" "95567f85708ffac8b34b6c6f2bdb49d8eb57e7704b7b416083c7f296dd40cd0b"}) for pod "liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a)"

测试总时间：

$ kubectl get po -w
NAME            READY   STATUS    RESTARTS   AGE
liveness-http   0/1     Running   21         99m
liveness-http   0/1     CrashLoopBackOff   21         101m
liveness-http   0/1     Running            22         106m
liveness-http   1/1     Running            22         106m
liveness-http   0/1     Running            22         106m
liveness-http   0/1     Running            23         109m
liveness-http   1/1     Running            23         109m
liveness-http   0/1     Running            23         109m
liveness-http   0/1     CrashLoopBackOff   23         112m
liveness-http   0/1     Running            24         117m
liveness-http   1/1     Running            24         117m
liveness-http   0/1     Running            24         117m

结论

不再调用活性探针检查

Liveness check在 Kubernetes 创建 pod 时创建，并在每次重新启动时重新创建Pod。在您的配置中，您已经设置了，initialDelaySeconds: 20因此在创建Kubernetes 后pod，Kubernetes 将等待 20 秒，然后它将调用livenessprobe 3 次（如您设置的那样failureThreshold: 3）。3 失败后，Kubernetes 会根据RestartPolicy. 同样在日志中，您将能够在日志中找到：

Mar 09 16:14:58 kubeadm kubelet[3855]: I0309 16:14:58.465470    3855 kuberuntime_manager.go:656] Container "liveness" ({"docker" "95567f85708ffac8b34b6c6f2bdb4
9d8eb57e7704b7b416083c7f296dd40cd0b"}) of pod liveness-http_default(8c87a08e-34aa-4bb1-be9b-fdca39a4562a): Container liveness failed liveness probe, will be restarted

为什么会重启？答案可以在Container probes中找到。

livenessProbe:指示容器是否正在运行。如果 liveness 探测失败，kubelet 会杀死容器，容器会受到其重启策略的约束。

中的默认重启策略是。因此，您的 pod 将一遍又一遍地重新启动。GKEAlways

已调用就绪探测检查，但间隔变长（最大间隔看起来约为 10 分钟）

我认为你已经得出了这个结论，因为你已经基于$ kubectl get events和$ kubectl describe po。在这两种情况下，默认事件都会在 1 小时后删除。在我的Tests部分中，您可以看到Readiness probe条目来自14:48:34until 16:04:24，因此每 10 秒 Kubernetes 调用一次Readiness Probe。

为什么 Liveness 探针没有运行，而 Readiness 探针的间隔发生了变化？

正如我在该Tests部分中向您展示的那样，Readiness probe没有改变。在这种情况下误导是使用$ kubectl events. 关于Liveiness Probe它仍在调用，但在 pod 之后只有 3 次created/ restarted。我还包括了$ kubectl get po -w. 重新pod创建时，您可能会在 kubelet 日志中找到那些liveness probes.

在我的计划中，我将创建警报策略，其条件如下：

  • 如果活性探测错误在 3 分钟内发生 3 次

如果liveness probe失败 3 次，使用您当前的设置，它将重新启动此 pod。在这种情况下，您可以使用 eachrestart创建一个alert.

Metric: kubernetes.io/container/restart_count
Resource type: k8s_container

您可以在 Stackoverflow 案例中找到一些有用的信息，Monitoring alert例如：

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