POD Design - Jobs and Cron Jobs

Question 1

What types of workloads do exist for instance?

Answer 1

• application
• web
• database
• reporting
• batch-processing
• analytics

Question 2

How are types of workloades abstractly different to each other?

Answer 2

• some need to keep on working
• some finish after a certain task / set of tasks

Question 3

What is the default behavior of Kubernetes in terms of pod lifecycle?

Answer 3

Wants to keep the pods running.
If a pods is in Status Completed it gets restarted, as often till a certain threshold is reached

Question 4

What specifies the Restart behavior of Kubernetes pods?

Answer 4

restartPolicy - by default set to Always

spec:
 containers:
  - image
    name
	  command
	restartPolicy: Always

Question 5

What are valid options for restartPolicy of a pod?

Answer 5

• Always
• Never
• OnFailure

Question 6

What is special about i.e batch-workloads?

Answer 6

• parallel working through a set of tasks
• we need a manager that makes sure, the work is done successfully

Question 7

What is the difference between a ReplicaSet and Jobs?

Answer 7

• ReplicaSet wants to keep the pods up running all the time
• Jobs keep pods running till completion

Question 8

How do we create a job?

Answer 8

job-definition.yaml:
~~~
apiVersion: batch/v1
kind: Job
metadata:
name: math-add-job
spec:
completions: 3
template:
spec:
containers:
- name:
image:
command:
restartPolicy: Never
~~~
Under template has a pod definition spec

kubectl create -f
kubectl get jobs

Question 9

How can you see the standard output of container?

Answer 9

kubectl logs pod-name pot.container-name

Question 10

What does the ‘completed’ addition change for a job?

Answer 10

• specified the amount of pods needed to be in Status Completed to see job as completed

Question 11

How are pods in jobs by default created?

Answer 11

one after the other

Question 12

How can we specify that a jobs runs pods in parallel?

Answer 12

apiVersion: batch/v1
kind: Job
metadata:
 name: math-add-job
spec:
 completions: 3
 parallelism: 3
 template:
   spec:
	   containers:
		   - name: 
		     image:
				 command:
		 restartPolicy: Never	

Question 13

What are CronJobs?

Answer 13

• a job that can be scheduled and run periodically
• for instance a job that creates a report and sends an email

Question 14

How does a cronjob yaml look like?

Answer 14

apiVersion: batch/v1
kind: CronJob
metadata:
 name: reporting-cronjob
spec:
  schedule "*/1 * * * *"
	jobTemplate:
	  spec:
		  completions: 3
			parallelism: 3
			template:
			  spec:
				  containers:
					  - image: reporting-tool
					    name: reporting-tool
					restartingPolicy: Never
	  
 

Question 15

How form has the schedule spec of a CronJob?

Answer 15

1. • • minute
2. • • hour
3. • • day of the month
4. • • month
5. day of the week

Question 16

How you specify the amount of fails after which a job should stop?

Answer 16

with backoffLimit under job-spec: