do replicas decrease traffic on a single node kubernetes cluster?

Question

I am new to the world of kubernetes. I am trying to implement kubernetes advantages on my personal project.

I have an api service in a docker container which fetches data from back end.

I plan on creating multiple replicas of this api service container on a single external port in the kubernetes cluster. Do replicas share traffic if they're on a single node ?

My end goal is to create multiple instances of this api service to make my application faster(users can access one of the multiple api services which should reduce traffic on a single instance).

Am i thinking right in terms of kubernetes functionality?

Answer 1

You are right, the multiple replicas of your API service will share the load. In Kubernetes, there is a concept of Services which will send traffic to the backend and in this case it is your api application running in the pods. By default, the choice of backend is random. Also, it doesn't matter whether the Pods are running on a single node or on different nodes, the traffic will be distributed randomly among all the Pods based on the labels .

This will also make your application highly available because you will use deployment for specifying the number of replicas and whenever the number of available replicas are less than the desired replicas, Kubernetes will provision new pods to meet the desired state.

Answer 2

If you add multiple instances / replicas of your web server it will share the load and will avoid single point of failure.

However to achieve this you will have to create and expose a Service. You will have to communicate using the Service endpoint and not using each pods IP directly.

A service exposes an endpoint. It has load balancing. It usually uses round robin to distribute load / requests to servers behind the service load balancer.

Kubernetes manages Pods. Pods are wrappers around containers. Kubernetes can schedule multiple pods on the same node(hardware) or across multiple nodes. Depends how you configure it. You can use Deployments to manage ReplicaSets which manage Pods.

Usually it is recommended to avoid managing pods directly. Pods can crash, stop abruptly. Kubectl will create a new for you automatically depending on the Replica Set config.

Using deployments you can do rolling updates also.

You can refer to Kubernetes Docs to read about this in detail.

Answer 3

Yes. It's called Braess's paradox .