Does DiskCache work with Netlify functions (AWS lambdas)?

[arpitdalal]

Docs say to install @next-boost/hybrid-disk-cache pkg but is that only for Vercel?
AWS Lambdas does support temp storage up to 512MB I believe, should I be able to cache my images there with this lib?

[Josh-McFarlin]

That's a great question. Since Lambda supports tmp, DiskCache should work. If you try it and it does not work, you may need to change the DiskCache dir, you can see this in the Vercel example.

However, tmp only holds up to 512 MB and it will eventually be reset between invocations. If you want better performance (cache more transformations, cache transformations longer, faster loading), a better option would be Lambda EFS. To use EFS, you would need to create your own Cache and provide it to the loader. If this is a small project / performance isn't critical, tmp will work fine and it's free.

Edit: Actually, I have never used EFS in Lambda before, so I was not sure how it worked. After reading up on it, you likely do not need a custom Cache. You should be able to create EFS through AWS, mount it to your Lambda, and use DiskCache, setting the path property to your mount location.

And yes, you would need to install that package. Unfortunately it cannot be included in Remix-Image, it must be installed separately.

The config for the EFS solution would be something along the lines of this:

const prodAwsUrl = process.env.DEPLOYMENT_URL;
const prodAwsEFS = process.env.EFS_DIR;

const config = {
  selfUrl: process.env.NODE_ENV === "development" ? "http://localhost:3000" : prodAwsUrl,
  cache: new DiskCache({
    path: process.env.NODE_ENV === "development" ? path.join(os.tmpdir(), "img") : prodAwsEFS,
  }),
  resolver: fetchImage,
  transformer: sharpTransformer,
  basePath: process.env.NODE_ENV === "development" ? "public" : "/",
};

[arpitdalal]

This sounds about right, I am not planning on going down the EFS road just yet but appreciate your quick little example which can be super helpful. I've a question regarding the selfUrl, how important is that to get it right? I can't find where to get that url in prod.

[Josh-McFarlin]

A good way to do selfUrl is an environment variable that is set to be the URL of your project once it is deployed, something like https://example.com

[arpitdalal]

A good way to do selfUrl is an environment variable that is set to be the URL of your project once it is deployed, something like https://example.com

Even if it is a server-less environment?