Kubernetes Cronjob Only Runs Half the Time

Question

I have cron job where i want it to be executed every 15 mins. The problem is that instead of veing executes every 15 mins, it gets executed every half an hour.

Whats the issue here?

This is my config file

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  labels:
    type: f-c
  name: f-c-p
  namespace: extract
spec:
  concurrencyPolicy: Forbid
  failedJobsHistoryLimit: 1
  jobTemplate:
    metadata:
      creationTimestamp: null
    spec:
      template:
        metadata:
          creationTimestamp: null
          labels:
            type: f-c
        spec:
          containers:
          - args:
            - /f_c.sh
            image: identifier.amazonaws.com/extract_transform:latest
            imagePullPolicy: Always
            env:
            - name: ENV
              value: prod
            - name: SLACK_TOKEN
              valueFrom:
                secretKeyRef:
                  key: slack_token
                  name: api-tokens
            - name: AWS_ACCESS_KEY_ID
              valueFrom:
                secretKeyRef:
                  key: aws_access_key_id
                  name: api-tokens
            - name: AWS_SECRET_ACCESS_KEY
              valueFrom:
                secretKeyRef:
                  key: aws_secret_access_key
                  name: api-tokens
            - name: F_ACCESS_TOKEN
              valueFrom:
                secretKeyRef:
                  key: f_access_token
                  name: api-tokens
            name: s-f-c
            resources: {}
            terminationMessagePath: /dev/termination-log
            terminationMessagePolicy: File
          dnsPolicy: ClusterFirst
          restartPolicy: Never
          schedulerName: default-scheduler
          securityContext: {}
          terminationGracePeriodSeconds: 30
  schedule: '*/15 * * * *'
  successfulJobsHistoryLimit: 1
  suspend: false
status: {}

Answer 1

The external circumstances prevents them from running as intended.

On the original cluster there were ~20k scheduled jobs. The built-in scheduler for Kubernetes is not yet capable of handling this volume consistently.

The maximum number of jobs that can be reliably run (within a minute of the time intended) may depend on the size of your master nodes.