Desired replicas vs actual replicas in Kubernetes - Quick Revision & Key Differences

Recall & Review

beginner

What does the term 'desired replicas' mean in Kubernetes?

Desired replicas refer to the number of pod instances you want running for a specific application or service, as defined in the deployment configuration.

beginner

What are 'actual replicas' in Kubernetes?

Actual replicas are the number of pod instances currently running in the cluster for a deployment or replica set.

intermediate

How does Kubernetes ensure the actual replicas match the desired replicas?

Kubernetes uses a controller that constantly monitors the actual replicas and creates or deletes pods to match the desired replicas automatically.

beginner

What command shows the desired and actual replicas of a deployment?

The command kubectl get deployment <deployment-name> shows desired replicas in the 'READY' column (e.g., 3/3) and actual available replicas under 'AVAILABLE'.

intermediate

What might cause the actual replicas to be less than the desired replicas?

Possible causes include insufficient resources, pod startup failures, or node issues preventing pods from running.

In Kubernetes, what does the 'desired replicas' number represent?

A The number of pods currently running

B The number of containers per pod

C The number of nodes in the cluster

D The number of pods you want running

Desired replicas are the number of pod instances you want running as set in the deployment.

Which Kubernetes component adjusts pods to match desired replicas?

A Controller Manager

B kubectl

C API Server

D Scheduler

The Controller Manager monitors and adjusts pods to match the desired replicas.

What kubectl command shows the desired and actual replicas of a deployment?

A kubectl get pods

B kubectl describe node

C kubectl get deployment <name>

D kubectl logs <pod>

kubectl get deployment shows desired and actual replicas.

If actual replicas are less than desired replicas, what could be a reason?

A Too many nodes available

B Pod startup failures

C kubectl is not installed

D Deployment is paused

Pod startup failures can cause fewer actual replicas than desired.

What does Kubernetes do if actual replicas exceed desired replicas?

A Deletes extra pods to match desired replicas

B Creates more pods

C Does nothing

D Restarts the cluster

Kubernetes deletes extra pods to keep actual replicas equal to desired replicas.

Explain the difference between desired replicas and actual replicas in Kubernetes.

Think about what you want vs what you have running.

Describe what happens when the actual replicas do not match the desired replicas in a Kubernetes deployment.

Consider Kubernetes as a system that fixes differences automatically.