Service selectors and labels in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a label in Kubernetes?

A label is a key-value pair attached to Kubernetes objects like pods. It helps organize and select groups of objects.

beginner

What does a service selector do in Kubernetes?

A service selector matches labels on pods to route network traffic to those pods.

intermediate

How do labels and selectors work together in a Kubernetes Service?

Labels identify pods, and selectors in the service find pods with matching labels to send traffic to them.

beginner

Can a service selector match multiple pods?

Yes, a service selector can match many pods if they share the same label key-value pairs.

intermediate

What happens if a service selector does not match any pods?

The service will have no endpoints and will not route traffic to any pods.

What is the purpose of labels in Kubernetes?

A To organize and select objects

B To store pod logs

C To define network policies

D To set resource limits

Labels are used to organize and select Kubernetes objects like pods.

What does a service selector use to find pods?

A Pod names

B Pod IP addresses

C Node names

D Labels on pods

Service selectors match labels on pods to route traffic.

If a service selector matches multiple pods, what happens?

A Traffic is load balanced across those pods

B Only the first pod receives traffic

C Traffic is sent to the node instead

D The service fails to start

The service load balances traffic across all pods matching the selector.

What is a key difference between labels and annotations?

A Annotations select pods; labels do not

B Labels are for selection; annotations are for metadata

C Labels are only for nodes

D Annotations control network traffic

Labels are used for selecting objects; annotations store metadata.

What happens if no pods match a service selector?

A The service routes traffic to all pods

B The service crashes

C The service has no endpoints and no traffic is routed

D The service creates new pods automatically

Without matching pods, the service has no endpoints and cannot route traffic.

Explain how Kubernetes uses labels and selectors to route traffic to pods.

Think about how a service finds the right pods to send requests.

Describe what happens when a service selector does not match any pods in Kubernetes.

Consider the service's ability to send traffic without matching pods.