Middleware running in Edge Function is broken by design. Proposal: Opt-out Middleware to use Node.js/Serverless Function runtime instead of Edge Function (or introduce caching in Edge Function)

[awinogrodzki]

Goals

1. User could decide whether to run Middleware in Edge Function or Serverless Function or possibly Node.js environment
2. OR – they would be able to cache repetitive requests inside Edge Function

Non-Goals

No response

Background

I am the author of next-firebase-auth-edge library.

The idea of this library is to setup simple authentication using Next.js Middleware as a single point of configuration.

I managed to make Firebase Authentication work in Edge environment, BUT...

In middleware, before I validate request using RequestCookies, I have to fetch Google x509 certificates from https://www.googleapis.com/robot/v1/metadata/x509/[email protected]. I need those certificates to act as public key, which I then verify token against.

Those certificates have expiry date, which means I cannot load them during build time.

Middleware runs on Edge Function which does not expose CacheStorage API

Which means – when app with next-firebase-auth-edge is deployed to Vercel environment, a call to https://www.googleapis.com/robot/v1/metadata/x509/[email protected] is made with each request.

There's no simple workaround for this issue.

It's possible to create proxy API Route to fetch Google certificates, and then call it from inside Middleware, but adding a dedicated API route each time a request has to be cached is counter-productive and definitely not a good idea for a library.

Which begs the question – why Middleware is called by Edge Function in the first place? If there's no possibility to cache inside Edge Function, it simply won't serve it's purpose.

The main idea behind Edge Function is to make round-trips fast. Eventually people will be forced to load things in Middleware before processing the request, which makes Edge Function more harmful than Node.js environment for Middleware, as they would have to make N+ roundtrips to different servers before actually returning a response.

My personal solution was to unfortunately move away from Vercel and use AWS Node.js environment to make CacheStorage usable in Middleware.

I also created #50102 issue on this topic

Proposal

Middleware file could export runtime variable with either one of following values: edge, serverless, nodejs

export const runtime = 'edge'; // 'nodejs' (default) | 'edge' | 'serverless'

I am interested in contributing

[awinogrodzki]

After some recent experiments, it seems that you can share global variables between multiple requests in Edge runtime, which basically solves the problem of caching between requests.

Closing the discussion

[awinogrodzki]

If anyone is interested in code examples, I shared some in this issue: #50102 (comment)