How do I balance load across multiple instances of an application with a Kubernetes ReplicaSet?

In this guide, we will demonstrate how to deploy a Kubernetes ReplicaSet to balance the load across multiple instances of an application. A ReplicaSet ensures that a specified number of pod replicas are running at any given time. This helps in achieving high availability and load balancing for your application.

We will create a ReplicaSet that maintains three replicas of an NGINX application and a Service to expose these replicas.

import * as pulumi from "@pulumi/pulumi";
import * as k8s from "@pulumi/kubernetes";

// Define the ReplicaSet
const appLabels = { app: "nginx" };

const replicaSet = new k8s.apps.v1.ReplicaSet("nginx-replicaset", {
    spec: {
        replicas: 3, // Number of replicas
        selector: { matchLabels: appLabels },
        template: {
            metadata: { labels: appLabels },
            spec: {
                containers: [{
                    name: "nginx",
                    image: "nginx:1.14.2",
                    ports: [{ containerPort: 80 }],
                }],
            },
        },
    },
});

// Define the Service to load balance traffic across the replicas
const service = new k8s.core.v1.Service("nginx-service", {
    metadata: { labels: appLabels },
    spec: {
        type: "LoadBalancer",
        ports: [{ port: 80, targetPort: 80 }],
        selector: appLabels,
    },
});

// Export the Service's IP address
export const serviceIP = service.status.loadBalancer.ingress[0].ip;

Key Points

ReplicaSet: Ensures the specified number of pod replicas are running.
Service: Exposes the ReplicaSet and balances traffic across the replicas.
Load Balancing: Achieved through the Service which distributes incoming traffic to the available pod replicas.

Summary

In this guide, we created a Kubernetes ReplicaSet to maintain three replicas of an NGINX application. We also created a Service to expose these replicas and balance the load. This setup ensures high availability and efficient load distribution for your application.

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