I have trouble setting the result value of a shell script to arguments for Kubernetes Cronjob regularly.
Is there any good way to set the value refreshed everyday?
I use a Kubernetes cronjob in order to perform some daily task.
With the cronjob, a Rust application is launched and execute a batch process.
As one of arguments for the Rust app, I pass target date (yyyy-MM-dd formatted string) as a command-line argument.
Therefore, I tried to pass the date value into the definition yaml file for cronjob as follows.
And I try setting ${TARGET_DATE} value with following script. In the sample.sh, the value for TARGET_DATE is exported.
cat sample.yml | envsubst | kubectl apply -f sample.shapiVersion: batch/v1beta1
kind: CronJob
metadata:
name: some-batch
namespace: some-namespace
spec:
schedule: "00 1 * * 1-5"
jobTemplate:
spec:
template:
spec:
containers:
- name: some-container
image: sample/some-image
command: ["./run"]
args: ["${TARGET_DATE}"]
restartPolicy: Never
I expected that this will create TARGET_DATE value everyday, but it does not change from the date I just set for the first time.
Is there any good way to set result of shell script into args of cronjob yaml regularly?
Thanks.
You can use init containers for that https://kubernetes.io/docs/concepts/workloads/pods/init-containers/
The idea is the following: you run your script that setting up this value inside init container, write this value into shared emptyDir volume. Then read this value from the main container. Here is example:
apiVersion: batch/v1beta1
kind: CronJob
metadata:
name: some-batch
namespace: some-namespace
spec:
schedule: "00 1 * * 1-5"
jobTemplate:
spec:
template:
spec:
initContainers:
- name: init-script
image: my-init-image
volumeMounts:
- name: date
mountPath: /date
command:
- sh
- -c
- "/my-script > /date/target-date.txt"
containers:
- name: some-container
image: sample/some-image
command: ["./run"]
args: ["${TARGET_DATE}"] # adjust this part to read from file
volumeMounts:
- name: date
mountPath: /date
restartPolicy: Never
volumes:
- name: date
emptyDir: {}