Services

Question 1

What is a service in kubernetes ?

Answer 1

Service is nothing but the Networking layer by which we can access one or more PODS.

Question 2

Can we rely on IP address of a POD to communicate with same ?

Answer 2

No.
If a POD is replaced, its IP address also gets changed.

Question 3

How should we access a POD, if it’s IP address keeps changing ?

Answer 3

using “Service”.

Question 4

Can we find out the IP address of a POD before it’s scheduling ?

Answer 4

No.
IP address is always allocated to the POD, once it gets scheduled. Hence, we cannot share same before it’s scheduling.

Question 5

What are the roles of a Service in Kubernetes ?

Answer 5

1. Accept the request from external user and pass same to one of POD
2. Load balance the request

Question 6

How a Service knows to which POD it needs to pass the request ?

Answer 6

Using Labels.
Both POD and Service must be using the “same” label to bound themselves. The label is the only way by which a Service load balances the requests between PODs.

Question 7

Does IP address of a service keeps changing ?

Answer 7

No, it remains fixed.

Question 8

On which Networking layer, does Service object works ?

Answer 8

Layer 4 (TCP/UDP over IP)

Question 9

How a frontend POD can communicate with Backend POD ?

Answer 9

The Frontend POD can call the IP address of Service which abstracts the accessiblity of Backend PODs.

Question 10

What are the different types of Services available in Kubernetes ?

Answer 10

1. ClusterIP service
2. NodePort Service
3. LoadBalancer Service
4. ExternalName service

Question 11

Can we access the “clusterIP” service from outside the K8 cluster ?

Answer 11

No.
ClusterIP service can only be accessed within the K8 cluster.

Question 12

What’s a clusterIP service ?

Answer 12

ClusterIP services is a K8 service which exposes the PODs within the cluster IPs.

Question 13

How a POD belongs to one service can access another POD belongs to another service ?

Answer 13

Using “Cluster IP” service.

Question 14

What’s a Node Port Service ?

Answer 14

NodePort Service is a K8 Service which exposes the PODs on Node’s IP address at a static port.

Question 15

Can we access a POD using NodePort service ?

Answer 15

Yes.
It provides access to POD via Node’ IP and static port

Question 16

Can a POD be able to access another POD using NodePort Service ?

Answer 16

No.
For accessing another service within the Cluster, Cluster IP service is needed.

Question 17

What’s a LoadBalancer Service ?

Answer 17

LoadBalancer Service is a service which exposes the PODs on an external Load Balancer.

Question 18

Do we need NodePort Service and Cluster IP service after creation of LoadBalancer Service ?

Answer 18

Yes.
During creation of LoadBalancer Service, NodePort Service and ClusterIP services gets automatically created.

Question 19

What’s an externalName Service ?

Answer 19

ExternalName service is the K8 service which “abstracts” any external service outside the cluster.

Question 20

How to perform port-forward on a POD using kubectl ?

Answer 20

> > > kubectl port-forward pod/my-nginx 8080:80

Question 21

How to perform port-forward on a deployment using kubectl ?

Answer 21

> > > kubectl port-forward deployment/my-nginx 8080

Question 22

How to perform port-forward on a service using kubectl ?

Answer 22

> > > kubectl port-forward service/my-nginx 8080

Question 23

Create the Service manifest template ?

Answer 23

apiVersion: apps/v1
kind: Service
metaData:
spec:
type:
selector:
ports

Question 24

What are the different types of the service we can provide in “service manifest”

Answer 24

1. ClusterIP
2. NodePort
3. LoadBalancer

Question 25

What are the different types of port we can provide in service manifest ?

Answer 25

1. Target Port
2. Service Port

Question 26

Create manifest for Cluster IP service object ?

Answer 26

apiVersion: v1
kind: Service
metadata:
name: nginx-clusterIP
spec:
type: ClusterIP
selector:
app: my-nginx
ports:
- port: 8080
targetPort: 80

Question 27

Create manifest for NodePort Service Object ?

Answer 27

apiVersion: v1
kind: Service
metadata:
name: nginx-nodeport
spec:
type: NodePort
selector:
app: my-nginx
ports:
- port: 80
targetPort: 80
nodePort: 31000

Question 28

Create manifest for LoadBalancer Service Object ?

Answer 28

apiVersion: 1
kind: Service
metadata:
name: nginx-loadbalancer
spec:
type: LoadBalancer
selector:
app: my-nginx
ports:
- name: “80”
port: 80
targetPort: 80