# Job

Job负责批处理任务，即仅执行一次的任务，它保证批处理任务的一个或多个Pod成功结束。

## Job Spec格式

* spec.template格式同Pod
* RestartPolicy仅支持Never或OnFailure
* 单个Pod时，默认Pod成功运行后Job即结束
* `.spec.completions`标志Job结束需要成功运行的Pod个数，默认为1
* `.spec.parallelism`标志并行运行的Pod的个数，默认为1
* `spec.activeDeadlineSeconds`标志失败Pod的重试最大时间，超过这个时间不会继续重试

一个简单的例子：

```yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: pi
spec:
  template:
    metadata:
      name: pi
    spec:
      containers:
      - name: pi
        image: perl
        command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never
```

```bash
$ kubectl create -f ./job.yaml
job "pi" created
$ pods=$(kubectl get pods --selector=job-name=pi --output=jsonpath={.items..metadata.name})
$ kubectl logs $pods -c pi
3.141592653589793238462643383279502...
```

## Bare Pods

所谓Bare Pods是指直接用PodSpec来创建的Pod（即不在ReplicaSets或者ReplicationController的管理之下的Pods）。这些Pod在Node重启后不会自动重启，但Job则会创建新的Pod继续任务。所以，推荐使用Job来替代Bare Pods，即便是应用只需要一个Pod。


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