How does Kubernetes manage load balancing

Question

I have 3 containers for the same microservice. How does Kubernetes manage load balancing between them?

Sarthak Varshney · Answer

Kubernetes manages load balancing using a concept called Services . Let’s say you have 3 containers running the same microservice — these are usually called Pods in Kubernetes. Kubernetes doesn't send traffic to them directly. Instead, you create a Service , which acts like a stable entry point (like a virtual IP address or DNS name) for your microservice. The most common type of service for internal communication is called a ClusterIP service. It automatically load balances traffic across all the pods behind it. Kubernetes keeps track of which pods are running and uses a built-in component called kube-proxy to route the incoming traffic to one of the available pods. Here’s how it works step-by-step: You define a Deployment (or some controller) to run 3 identical pods. You create a Service (like my-service ) that selects these pods using labels. When another service or client inside the cluster sends a request to my-service , Kubernetes randomly or round-robin distributes that request to one of the 3 pods. Kubernetes automatically monitors the health of pods and distributes incoming traffic across them, eliminating the need for special manual configurations. For external access, Kubernetes provides options such as LoadBalancer or Ingress, depending on your deployment configuration. Simple Explanation Kubernetes uses something called a Service to manage load balancing. Let’s say you deploy 3 pods running the same microservice. Kubernetes can automatically balance the traffic between them using a Service , so no single pod gets overloaded. Step-by-Step with YAML 1. Create a Deployment with 3 replicas (pods) apiVersion: apps/v1 kind: Deployment metadata: name: my-microservice spec: replicas: 3 selector: matchLabels: app: my-microservice template: metadata: labels: app: my-microservice spec: containers: - name: my-container image: myusername/my-microservice:latest ports: - containerPort: 8080 This will launch 3 pods running the same container image. 2. Create a Service to load balance between the pods apiVersion: v1 kind: Service metadata: name: my-service spec: selector: app: my-microservice ports: - protocol: TCP port: 80 # Port on the service targetPort: 8080 # Port on the pods type: ClusterIP # Internal load balancing within the cluster This Service will expose a stable IP (or DNS like my-service.default.svc.cluster.local ) that other pods can call. Kubernetes will automatically route traffic to one of the 3 pods using round-robin or random strategy (depending on configuration and setup). Optional: Expose to the Outside World If you want to expose it outside the cluster: apiVersion: v1 kind: Service metadata: name: my-service spec: selector: app: my-microservice ports: - protocol: TCP port: 80 targetPort: 8080 type: LoadBalancer This will ask your cloud provider (like AWS, GCP, Azure) to create an external load balancer that forwards traffic to the 3 pods inside your cluster. So, you don't have to manually configure anything special - Kubernetes takes care of keeping track of the healthy pods and evenly spreading the traffic between them.

How does Kubernetes manage load balancing

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