Is there a way to know at which time pod should be executed?

Question

Supose I have cronjob in Kubernetes that is scheduled each 30 minutes (10:00, 10:30, 11:00 etc.)

Supose also that due to resources job started at 10:05 instead of 10:00 or even 11:00 instead of 10:00

Is there an enviroment variable/option to know inside running pod at which time this pod was expected to be running?

Consider script that downloads everything from last hour - instead of 2 pods getting data from 10:00 to 11:00, I want option to utilize information of scheduled time;

anticipating questions - yes, I know i could do some queue/coding to avoid this problem, but I'm interested only in plain kubernetes possibilities.

score 0 · Answer 1 · answered May 07 '19 at 15:09

If you do kubectl describe cj <name_of_cronjob> it will show you Last Schedule Time

Last Schedule Time: Tue, 07 May 2019 16:58:00 +0200

also You will see the events:

  Type    Reason            Age    From                Message
  ----    ------            ----   ----                -------
  Normal  SuccessfulCreate  2m25s  cronjob-controller  Created job hello-1
  Normal  SawCompletedJob   2m15s  cronjob-controller  Saw completed job: hello-1
  Normal  SuccessfulCreate  85s    cronjob-controller  Created job hello-2
  Normal  SawCompletedJob   75s    cronjob-controller  Saw completed job: hello-2
  Normal  SuccessfulCreate  24s    cronjob-controller  Created job hello-3
  Normal  SawCompletedJob   14s    cronjob-controller  Saw completed job: hello-3

You can add date as a command at the beginning on your CronJob it will tell you in logs when it started.

Yaml might look like this:

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: hello
spec:
  schedule: "* * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: hello
            image: busybox
            args:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure

You can check for logs which will show you the data being executed.

$ kubectl get pods
NAME                     READY   STATUS      RESTARTS   AGE
hello-1-nrf5b   0/1     Completed   0          3m
hello-2-kk8t5   0/1     Completed   0          119s
hello-3-tpffz   0/1     Completed   0          59s
$ kubectl logs pods/hello-2-kk8t5
Tue May  7 14:58:09 UTC 2019
Hello from the Kubernetes cluster

You can see this example and other in the Kubernetes documentation Running Automated Tasks with a CronJob.

date in this example won't be connected to time of scheduling, since there may be pulling image, before container run, date will be different. But maybe allowing pod to read events from K8S would be sufficient to complete this task. — maque, May 08 '19 at 11:23
if you provide the sufficient roles via RBAC and install kubectl binaries that can work — Crou, May 28 '19 at 15:16

Is there a way to know at which time pod should be executed?

1 Answers1