How Do I Create a Kubernetes Deployment Patch?

Introduction

Kubernetes is a powerful platform for managing containerized applications, and sometimes you need to update your deployments to reflect changes in configuration or scaling requirements. A deployment patch allows you to modify existing deployments without having to recreate them from scratch. In this guide, we will explore how to create a Kubernetes deployment patch using Pulumi, a modern infrastructure as code platform. This approach helps streamline updates by allowing you to apply changes declaratively.

Step-by-Step Guide to Creating a Kubernetes Deployment Patch

To create a Kubernetes deployment patch, you can use Pulumi to define and apply a patch to an existing Kubernetes deployment. This patch can update various attributes of the deployment, such as the number of replicas or container images.

Below is a Pulumi program written in TypeScript that demonstrates how to create and apply a patch to a Kubernetes deployment:

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

// Define the existing deployment to be patched
const existingDeployment = new k8s.apps.v1.Deployment("existing-deployment", {
    metadata: {
        name: "my-deployment",
        namespace: "default",
    },
    spec: {
        replicas: 3,
        selector: {
            matchLabels: {
                app: "my-app",
            },
        },
        template: {
            metadata: {
                labels: {
                    app: "my-app",
                },
            },
            spec: {
                containers: [
                    {
                        name: "my-container",
                        image: "nginx:1.14.2",
                    },
                ],
            },
        },
    },
});

// Define the patch to be applied
const deploymentPatch = new k8s.apps.v1.DeploymentPatch("deployment-patch", {
    metadata: {
        name: "my-deployment",
        namespace: "default",
    },
    spec: {
        replicas: 5, // Update the number of replicas
        template: {
            spec: {
                containers: [
                    {
                        name: "my-container",
                        image: "nginx:1.16.1", // Update the container image
                    },
                ],
            },
        },
    },
}, { dependsOn: existingDeployment });

export const deploymentName = existingDeployment.metadata.name;
export const patchedReplicas = deploymentPatch.spec.replicas;
export const patchedImage = deploymentPatch.spec.template.spec.containers[0].image;

Key Points:

• Existing Deployment: The code defines an existing Kubernetes deployment named “my-deployment” in the “default” namespace.
• Patch Definition: A deployment patch is defined using DeploymentPatch to update the number of replicas and the container image of the existing deployment.
• Dependencies: The patch depends on the existing deployment to ensure it is applied correctly.

Conclusion

In this example, we demonstrated how to create a Kubernetes deployment patch using Pulumi. By updating the number of replicas and the container image of an existing deployment, you can efficiently manage changes. Using the DeploymentPatch resource helps maintain a declarative approach to managing Kubernetes deployments, ensuring that your infrastructure is both flexible and scalable.