A Cron Job creates Jobs on a time-based schedule. One CronJob object is like one line of a crontab (cron table) file. It runs a job periodically on a given schedule. The schedule of CronJob can be set, for example,
*/1 * * * * means excute the job every 1 minute, the format of the timing plan please reference CRON.
Sign in with project-regular, enter into one project (e.g. demo-namespace), then select Workload → CronJobs.
1.1. Click Create CronJob button, then fill in the basic information in the pop-up window. There are two ways to create a CronJob, i.e. fill in the creation table and edit mode. The following mainly introduces each step within creation table. If you prefer edit mode, you can click on the edit mode, it supports the yaml and json formats. Edit mode makes it easy for users who are used to command operations.
1.2. On the basic information page, enter the name of the CronJob, you can also fill in the description as required.
Click Advanced Options to set CronJob limitations, there are 4 fields as following:
concurrencyPolicy: Optional, it specifies how to treat concurrent executions of a job that is created by this cron job. the spec may specify only one of the following concurrency policies:
Click Next when you're done.
CronJob has specified following 4 kind of settings to handling pod lifecycle.
Click Next to skip to the next step.
3.1. RestartPolicy can only specify Never or OnFailure, when the job is not completed:
3.2. Click on the Add Container button, add a container image as needed. The image defined in the template is pulling from the DockerHub by default. Enter the name of the container and the corresponding image name. The image name generally needs to be specified with its tag, such as
In order to realize the effective scheduling and allocation of resources in the cluster and improve resources utilization, the platform uses requests and limits to allocate resources. Request is usually the minimum resource requirement used by the container, and limit is usually the maximum value of the resource. Setting it to 0 means that there is no restriction on the resources used. Request can ensure that the pod has enough resources to run, and limit is to prevent a Pod from using resources unrestricted，causing other Pods to crash.
Table 1: CPU Quota Description
|Requests||A request is the amount of that CPU resources that the system will guarantee for the container, and Kubernetes will use this value to decide on which node to place the pod.|
|Limits||A limit is the maximum amount of CPU resources that Kubernetes will allow the container to use.|
Table 2: Memory Quota Description
|Requests||A request is the amount of that memory resources that the system will guarantee for the container, and Kubernetes will use this value to decide on which node to place the pod.|
|Limits||A limit is the maximum amount of memory resources that Kubernetes will allow the container to use. If the memory usage exceeds this limit, the container may be killed.|
2.2. If the user has further requirements, click on the Advanced Options button.
Environment Variables: you can define an argument for a Pod using any of the techniques available for defining environment variables, including ConfigMaps and Secrets, which has the same effect as the "ENV" in the Dockerfile, providing great flexibility for creating workloads.
Click Save when setup is complete.
Then Click Next when you're done.
Job suppots totally 3 kind of volumes, i.e. Persistent Storage Volume, Temporary Storage Volume (EmptyDir) and Reference Configuration Center.
Persistent storage volumes can be used to save user's persist data, Add Existing Volume means you need to create volumes in advance, see Create Persistent Storage Volume.
The temporary storage volume represents emptyDir, which is first created when a Pod is assigned to a Node, and exists as long as that Pod is running on that node. When a Pod is removed from a node for any reason, the data in the emptyDir is deleted forever.
It also supports for configuring the key-value pairs in ConfigMap or Secret via reference configuration center.
A secret volume is used to pass sensitive information, such as passwords, to Pods. Secret volumes are backed by tmpfs (a RAM-backed filesystem) so they are never written to non-volatile storage.
ConfigMap is used to store configuration data in the form of key-value pairs. The configMap resource provides a way to inject configuration data into Pods. The data stored in a ConfigMap object can be referenced in a volume of type configMap and then consumed by containerized applications running in a Pod.
Click on the Next button when you're done.
Labels are key/value pairs that are attached to objects, such as pods. Labels are intended to be used to specify identifying attributes of objects that are meaningful and relevant to users. Labels can be used to organize and to select subsets of objects, each object can have a set of key/value labels defined, such as
relase: stable ; tier: cronjob.
Click on the Next button when you're done.
For the pod to be eligible to run on a node, the node must have each of the indicated key-value pairs as labels (it can have additional labels as well). The user can specify the node on which the Pod is expected to run by setting one or more sets of key-value pairs or select node directly. When not specified, the Pod will likely be scheduled to any node in the cluster that meets the resource scheduling criteria.
Click Create to complete the creation of the CronJob. The status display “Updating” is due to it's pulling the image. After the image pull succeeds, the status will display “Running”.