Jobs and CronJobs

Overview

In Kubernetes, there are two types of jobs: jobs and CronJobs.

A job is a resource object used to control batch tasks. Jobs start and terminate at the specified time, unlike long-running services such as Deployments and StatefulSets, which run continuously unless terminated. Pods managed by a job are automatically removed after successfully completing their tasks, based on the specified settings. The success flag varies depending on the spec.completions policy. A single-pod job is considered successful if one pod completes successfully. A job with a fixed success count is considered successful if N pods complete successfully. A queue job is considered successful based on the global success confirmed by the application.

A CronJob runs at the specified time. It is similar with Linux crontab. The details are as follows:

• A CronJob runs only once at the specified time.
• A CronJob runs periodically at the specified time.

A CronJob is typically used to:

• Schedule jobs at the specified time.
• Create jobs to run periodically, for example, database backup and email sending.

Creating a Job

A job runs pods that perform one-off batch tasks. The pods are automatically removed after successfully completing their tasks. Before creating a workload, you can run a job to upload an image to the image repository.

1. (Optional) If you use a private image to create your job, upload the container image to the image repository.
2. Log in to the UCS console and access the cluster console. In the navigation pane, choose Workloads. Click the Jobs tab. In the upper right corner, click Create from Image.
3. Configure workload parameters.
   Basic Info

   • Workload Type: Select Job.
   • Workload Name: Enter a workload name.
   • Namespace: Select the namespace of the workload. The default value is default. You can also click Create Namespace to create one. For details, see Creating a Namespace.
   • Pods: Enter the number of pods.
   Container Settings

   • Container Information: Multiple containers can be configured in a pod. You can click Add Container on the right to configure multiple containers for the pod.
     • Basic Info: See Table 1.

       Table 1 Basic information parameters

       Parameter	Description
       Container Name	Name the container.
       Image Name	Click Select Image and select the image used by the container. My Images: images in the image repository of the current region. If no image is available, click Upload Image to upload an image. Open Source Images: official images in the open source image repository. Shared Images: private images shared by another account. For details, see Sharing Private Images.
       Image Tag	Select the image tag to be deployed.
       Pull Policy	Image update or pull policy. If you select Always, the image is pulled from the image repository each time. If you do not select Always, the existing image of the node is preferentially used. If the image does not exist in the node, it is pulled from the image repository.
       CPU Quota	Request: minimum number of CPU cores required by a container. The default value is 0.25 cores. Limit: maximum number of CPU cores available for a container. Do not leave Limit unspecified. Otherwise, intensive use of container resources will occur and your workload may exhibit unexpected behavior.
       Memory Quota	Request: minimum amount of memory required by a container. The default value is 512 MiB. Limit: maximum amount of memory available for a container. When memory usage exceeds the specified memory limit, the container will be terminated. For details about Request and Limit of CPU or memory, see Setting Container Specifications.
       Heterogeneous Resource	If you have installed the gpu-device-plugin add-on, you can configure the GPU limit. For details, see GPU Scheduling. If you have installed the huawei-npu add-on, you can configure the NPU limit. For details, see NPU Scheduling. NOTE: This parameter is only available for workloads in on-premises clusters.
       Init Container	Select whether to use the container as an init container. An init container is a special container that runs before app containers in a pod. For details, see Init Containers.
       Privileged Container	Programs in a privileged container have certain privileges. If Privileged Container is enabled, the container is assigned privileges. For example, privileged containers can manipulate network devices on the host machine and modify kernel parameters.

     • Lifecycle: The lifecycle callback functions can be called in specific phases of the container. For example, if you want the container to perform a certain operation before stopping, set the corresponding function. Currently, lifecycle callback functions, such as startup, post-start, and pre-stop functions, are provided. For details, see Setting Container Lifecycle Parameters.
     • Environment Variable: Environment variables affect the way a running container will behave. Configuration items set by environment variables will not change if the pod lifecycle ends. For details, see Setting Environment Variables.
     • Data Storage: Store container data using Local Volumes and PersistentVolumeClaims (PVCs). You are advised to use PVCs to store workload pod data on a cloud volume. If you store pod data on a local volume and a fault occurs on the node, the data cannot be restored. For details about container storage, see Container Storage.
   • Image Access Credential: Select the credential for accessing the image repository. This credential is used only for accessing a private image repository. If the selected image is a public image, you do not need to select a secret. For details on how to create a secret, see Creating a Secret.
   Advanced Settings

   • Labels and Annotations: You can click Confirm to add a label or annotation for the pod. The key of the new label or annotation cannot be the same as that of an existing one.
   • Job Settings
     • Parallel Pods: Maximum number of pods that can run in parallel during job execution. The value cannot be greater than the total number of pods in the job.
     • Timeout (s): Once a job reaches this time, the job status becomes failed and all pods in this job will be deleted. If you leave this parameter blank, the job will never time out.

4. View the job in the job list.

   If the job status is Processing, the job has been created.

Creating a CronJob

A CronJob creates jobs that run repeatedly on a given schedule. The jobs automatically exit after successfully completing their tasks. For example, you can perform time synchronization for all active nodes at the specified time.

1. (Optional) If you use a private image to create your cron job, upload the container image to the image repository.
2. Log in to the UCS console and access the cluster console. In the navigation pane, choose Workloads. Click the CronJobs tab. In the upper right corner, click Create Workload.
3. Configure workload parameters.
   Basic Info

   • Workload Type: Select CronJob.
   • Workload Name: Enter a workload name.
   • Namespace: Select the namespace of the workload. The default value is default. You can also click Create Namespace to create one. For details, see Creating a Namespace.
   Container Settings

   • Container Information: Multiple containers can be configured in a pod. You can click Add Container on the right to configure multiple containers for the pod.
     • Basic Info: See Table 2.

       Table 2 Basic information parameters

       Parameter	Description
       Container Name	Name the container.
       Image Name	Click Select Image and select the image used by the container. My Images: images in the image repository of the current region. If no image is available, click Upload Image to upload an image. Open Source Images: official images in the open source image repository. Shared Images: private images shared by another account. For details, see Sharing Private Images.
       Image Tag	Select the image tag to be deployed.
       Pull Policy	Image update or pull policy. If you select Always, the image is pulled from the image repository each time. If you do not select Always, the existing image of the node is preferentially used. If the image does not exist in the node, it is pulled from the image repository.
       CPU Quota	Request: minimum number of CPU cores required by a container. The default value is 0.25 cores. Limit: maximum number of CPU cores available for a container. Do not leave Limit unspecified. Otherwise, intensive use of container resources will occur and your workload may exhibit unexpected behavior.
       Memory Quota	Request: minimum amount of memory required by a container. The default value is 512 MiB. Limit: maximum amount of memory available for a container. When memory usage exceeds the specified memory limit, the container will be terminated. For details about Request and Limit of CPU or memory, see Setting Container Specifications.
       Heterogeneous Resource	If you have installed the gpu-device-plugin add-on, you can configure the GPU limit. For details, see GPU Scheduling. If you have installed the huawei-npu add-on, you can configure the NPU limit. For details, see NPU Scheduling. NOTE: This parameter is only available for workloads in on-premises clusters.
       Init Container	Select whether to use the container as an init container. An init container is a special container that runs before app containers in a pod. For details, see Init Containers.
       Privileged Container	Programs in a privileged container have certain privileges. If Privileged Container is enabled, the container is assigned privileges. For example, privileged containers can manipulate network devices on the host machine and modify kernel parameters.

     • Lifecycle: The lifecycle callback functions can be called in specific phases of the container. For example, if you want the container to perform a certain operation before stopping, set the corresponding function. Currently, lifecycle callback functions, such as startup, post-start, and pre-stop functions, are provided. For details, see Setting Container Lifecycle Parameters.
     • Environment Variables: Environment variables affect the way a running container will behave. Configuration items set in environment variables will not change if the pod lifecycle ends. For details, see Setting Environment Variables.
   • Image Access Credential: Select the credential for accessing the image repository. This credential is used only for accessing a private image repository. If the selected image is a public image, you do not need to select a secret. For details on how to create a secret, see Creating a Secret.

   Execution Settings

   • Concurrency Policy: There are three options.
     • Forbid: A new job cannot be created before the previous job is completed.
     • Allow: The CronJob allows multiple jobs to run concurrently. Each job independently consumes cluster resources.
     • Replace: If a new job is scheduled to start while the previous job is still running, the new job will replace the currently running job.
   • Policy Settings: specifies when a new CronJob is executed. Policy settings in YAML are implemented using cron expressions.
     • A CronJob is executed at a fixed interval. The unit can be minute, hour, day, or month. For example, if a CronJob is executed every 30 minutes, its cron expression is */30 * * * *. The job will be executed at 30-minute intervals, starting from the top of the hour, for example, 00:00:00, 00:30:00, 01:00:00, and ....
     • A CronJob is executed monthly. For example, if a CronJob is executed at 00:00 on the first day of each month, its cron expression is 0 0 1 */1 *. The CronJob will be executed at ****-01-01 00:00:00, ****-02-01 00:00:00, and ....
     • A CronJob is executed weekly. For example, if a CronJob is executed at 00:00 every Monday, its cron expression is 0 0 * * 1. The CronJob will be executed at ****-**-01 00:00:00 on Monday, ****-**-08 00:00:00 on Monday, and ....
     • Custom Cron Expression: For details about how to use cron expressions, see cron.
     

     • If a CronJob is executed monthly and the specified date does not exist in that month, the CronJob will not be executed in that month. For example, if the date is set to 30, the CronJob will not be executed in February.
     • Due to the definition of the cron expression, the fixed period is not strictly periodic. Time values are divided into equal periods starting from 0. For example, when the unit is minutes, values range from 0 to 59. If the total range is not evenly divisible by the period, the final period resets to start from 0 again. Therefore, an accurate period can be represented only when the period can be evenly divided.

       Take a CronJob that runs hourly as an example. If an interval can divide 24 hours exactly, such as /2, /3, /4, /6, /8, and /12, the period can be accurately represented. However, if a different period is used, the last period will reset at the beginning of each new day. For example, if the cron expression is * */12 * * *, the CronJob will run at 00:00:00 and 12:00:00 every day. Similarly, if the cron expression is * */13 * * *, the CronJob will run at 00:00:00 and 13:00:00 every day. Note that the last period will reset at 00:00:00 on the following day, even if it has not reached 13 hours.

   • Job Records: You can set the number of jobs that are successfully executed or fail to be executed. If the values are set to 0, none of the jobs will be retained after they finish.
   Advanced Settings

   • Labels and Annotations: You can click Add to add a pod label or annotation. The key of the new label or annotation cannot be the same as that of an existing one.

4. View the CronJob in the CronJob list.

   If the CronJob status is Started, the CronJob has been created.

Related Operations

• View Events: You can set search criteria, such as the time segment during which an event is generated or the event name, to view related events.
• Pods/Jobs: View the information about the target pod/job.
  • View Events: Event information generated by the pod, which is stored for one hour.
  • Pods: View the pod name, status, and restart times.
  • View YAML: View the YAML file of the pod.
  • Delete: Delete the pod.
• View/Edit YAML: View or edit the YAML file of the workload.
• Delete: Delete the CronJob.
• Stop (for CronJobs only): Stop the CronJob.