1. Using kubernetes autoscaling with externaldns.k8s.io

    TypeScript

    Autoscaling in Kubernetes is a mechanism that automatically adjusts the number of running Pods in response to the resource usage of your applications. With autoscaling, your applications can scale out or scale back in, ensuring that Pods are only used when needed, enhancing resource efficiency.

    To enable autoscaling in a Kubernetes cluster, you will typically use the HorizontalPodAutoscaler (HPA) resource. The HPA adjusts the number of replicas in a Deployment or ReplicaSet based on the current CPU or memory usage.

    For managing DNS entries of services or ingresses within your cluster, you can use ExternalDNS. ExternalDNS syncs exposed Kubernetes Services and Ingresses with DNS providers to make them discoverable. However, the autoscaling feature in Kubernetes and the ExternalDNS service operate independently – autoscaling manages the number of Pods, whereas ExternalDNS is concerned with DNS records.

    The code below defines a HorizontalPodAutoscaler in a Kubernetes cluster and assumes you have ExternalDNS set up to manage DNS records. It does not configure ExternalDNS, as that requires specifics about your DNS provider and domain setup.

    Here's a simple Pulumi TypeScript program that demonstrates how to define a HorizontalPodAutoscaler resource:

    import * as k8s from "@pulumi/kubernetes"; // Define the configuration for our HorizontalPodAutoscaler. const hpa = new k8s.autoscaling.v1.HorizontalPodAutoscaler("hpa-example", { metadata: { name: "example-hpa" }, spec: { scaleTargetRef: { apiVersion: "apps/v1", kind: "Deployment", name: "example-deployment" // Name of the deployment you want to scale. }, minReplicas: 1, // Minimum number of Pods you want to run. maxReplicas: 10, // Maximum number of Pods you want to run. targetCPUUtilizationPercentage: 50, // Target CPU utilization threshold to trigger scaling. }, }); // Export the name of the HPA export const hpaName = hpa.metadata.name;

    To explain the program:

    • The @pulumi/kubernetes package is imported to access Kubernetes resources.
    • A new HorizontalPodAutoscaler is created with the k8s.autoscaling.v1.HorizontalPodAutoscaler constructor.
    • metadata specifies the name of the HPA resource in Kubernetes.
    • spec comprises the following fields:
      • scaleTargetRef designates the Deployment resource that the HPA will manage.
      • minReplicas defines the minimum number of Pods that should always be running.
      • maxReplicas defines the maximum number of Pods to which the Deployment can scale.
      • targetCPUUtilizationPercentage defines the target average CPU utilization across all Pods at which the Deployment will scale up or down.

    Please note that for the HPA to function correctly:

    • You need a Deployment with the name example-deployment (or change it to the actual Deployment you have).
    • Your cluster must have metrics-server installed so it can gather the necessary metrics for autoscaling.
    • The Pods must have CPU requests and limits defined for CPU-based autoscaling to function properly.

    To incorporate ExternalDNS within your setup, you would create and manage DNS records using an appropriate provider. ExternalDNS would then automatically create or remove the appropriate DNS records when you expose your services or create ingress resources in the Kubernetes cluster.

    For more detailed information about autoscaling in Kubernetes, you can refer to the Kubernetes documentation on Horizontal Pod Autoscaling, and for ExternalDNS, visit the ExternalDNS GitHub repository.


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