回答问题

我在 kubernetes 中使用 schedule(8 * * * *) 创建了一个Cronjob,job 的backoffLimit默认为 6,pod 的RestartPolicy为Never,pod 被故意配置为 FAIL。据我了解,(对于带有restartPolicy : Never的 podSpec)作业控制器将尝试创建backoffLimit数量的 pod,然后将作业标记为Failed,因此,我预计在Error状态下会有 6 个 pod。

这是实际 Job 的状态:

status:
  conditions:
  - lastProbeTime: 2019-02-20T05:11:58Z
    lastTransitionTime: 2019-02-20T05:11:58Z
    message: Job has reached the specified backoff limit
    reason: BackoffLimitExceeded
    status: "True"
    type: Failed
  failed: 5

为什么只有 5 个失败的 pod 而不是 6 个?还是我对backoffLimit的理解不正确?

Answers

简而言之:您可能看不到所有创建的 pod,因为 cronjob 中的计划周期太短。

如文档中所述:

与作业关联的失败 Pod 由作业控制器重新创建,并以指数回退延迟(10 秒、20 秒、40 秒......)的上限为 6 分钟。如果在 Job 的下一次状态检查之前没有出现新的失败 Pod,则将重置回退计数。

如果在作业控制器有机会重新创建 pod 之前安排了新作业(考虑到上次失败后的延迟),作业控制器会重新从一个开始计数。

我使用以下.yaml在 GKE 中重现了您的问题:

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: hellocron
spec:
  schedule: "*/3 * * * *" #Runs every 3 minutes
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: hellocron
            image: busybox
            args:
            - /bin/cat
            - /etc/os
          restartPolicy: Never
      backoffLimit: 6
  suspend: false

此作业将失败,因为文件/etc/os不存在。

这是其中一项工作的kubectl describe输出:

Name:           hellocron-1551194280
Namespace:      default
Selector:       controller-uid=b81cdfb8-39d9-11e9-9eb7-42010a9c00d0
Labels:         controller-uid=b81cdfb8-39d9-11e9-9eb7-42010a9c00d0
                job-name=hellocron-1551194280
Annotations:    <none>
Controlled By:  CronJob/hellocron
Parallelism:    1
Completions:    1
Start Time:     Tue, 26 Feb 2019 16:18:07 +0100
Pods Statuses:  0 Running / 0 Succeeded / 6 Failed
Pod Template:
  Labels:  controller-uid=b81cdfb8-39d9-11e9-9eb7-42010a9c00d0
           job-name=hellocron-1551194280
  Containers:
   hellocron:
    Image:      busybox
    Port:       <none>
    Host Port:  <none>
    Args:
      /bin/cat
      /etc/os
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Events:
  Type     Reason                Age   From            Message
  ----     ------                ----  ----            -------
  Normal   SuccessfulCreate      26m   job-controller  Created pod: hellocron-1551194280-4lf6h
  Normal   SuccessfulCreate      26m   job-controller  Created pod: hellocron-1551194280-85khk
  Normal   SuccessfulCreate      26m   job-controller  Created pod: hellocron-1551194280-wrktb
  Normal   SuccessfulCreate      26m   job-controller  Created pod: hellocron-1551194280-6942s
  Normal   SuccessfulCreate      25m   job-controller  Created pod: hellocron-1551194280-662zv
  Normal   SuccessfulCreate      22m   job-controller  Created pod: hellocron-1551194280-6c6rh
  Warning  BackoffLimitExceeded  17m   job-controller  Job has reached the specified backoff limit

请注意创建 podhellocron-1551194280-662zv和hellocron-1551194280-6c6rh之间的延迟。