Invalidating outdated content for dynamic updates

Question

Pulumi · Accepted Answer

When you serve content via a Content Delivery Network (CDN), it's common to cache content to improve performance. However, there will be cases when you need to update the content and ensure that all users receive the most up-to-date version, which requires invalidating the outdated cached content.

AWS CloudFront is a widely-used CDN service that supports invalidation of cached content. Using Pulumi, you can automate the process of invalidation when you deploy changes to your content. Below, I will show you how to create a simple Pulumi program written in TypeScript that invalidates a CloudFront distribution's cache.

The following program assumes that you already have a CloudFront distribution set up and know the distribution ID. We will be using the `aws.cloudfront.Distribution` resource to interact with CloudFront, and to create invalidation, we will use the `aws.cloudfront.Invalidation` resource.

Here is how you can create an invalidation for your CloudFront distribution:

1. **Set up your Pulumi project**: Before running this program, ensure you have a Pulumi project set up and configured with your AWS credentials.

2. **Add the necessary package**: You'll need the `@pulumi/aws` package, which you can install with your package manager (e.g. `npm` or `yarn`).

3. **Create the invalidation resource**: Use the `aws.cloudfront.Invalid` resource to define an invalidation. The `distributionId` property is the ID of the distribution you want to invalidate, and the `paths` property contains the list of path patterns that specify the files to invalidate.

Now, let's proceed with the Pulumi program:

```typescript
import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

// Configuration variables for the CloudFront distribution and the paths to invalidate.
// Replace 'your-distribution-id' with your actual CloudFront distribution ID.
const distributionId = "your-distribution-id";
const pathsToInvalidate = ["/*"];  // Invalidate all files

const invalidation = new aws.cloudfront.Invalidation("myInvalidation", {
    distributionId: distributionId,
    paths: pathsToInvalidate
});

// Export the ID of the invalidation
export const invalidationId = invalidation.id;

// To run the program, you would execute `pulumi up` in your terminal,
// which will prompt you to confirm the action before proceeding.
```

In this program:
- We import Pulumi's AWS module to interact with AWS services.
- We declare the distribution ID and paths as variables for easy reuse and modification.
- We create a new invalidation by instantiating `aws.cloudfront.Invalidation`.
- We export the `invalidationId` for reference, which you could use for logging or auditing purposes.

Remember to replace `'your-distribution-id'` with the actual ID of the CloudFront distribution you intend to invalidate. The path `["/*"]` is set to invalidate all the content from your CDN, but you can specify more precise paths if you need to invalidate specific files.

To deploy this invalidation, you will run `pulumi up` in your terminal, which will perform the invalidation. This is usually done as part of a deployment process when you've updated the content that your CloudFront distribution serves.