vielmetti / fly-replay-demo

Example app to use Fly-Replay to route /blog requests to another app

fly-replay-demo

Example app to use Fly-Replay to route /blog requests to another app.

We used NodeJS for simplicity but any language that can create a HTTP server will do.

How this works?

This repo contains two fly apps: fly-replay-app and fly-replay-app. The blog app doesn't need to know anything about how Fly-Replay works, the real magic happens in fly-replay-app.

At fly-replay-app index.js we have the following snippet:

app.all('/blog*', function replayToBlog(req, res) {
  res.set('Fly-Replay', 'app=fly-replay-blog')
  res.status(204).send('')
})

All requests that go to any path that match /blog* will receive an empty response with the header Fly-Replay containing the value 'app=fly-replay-blog'. Fly proxy will understand that and will replay the exact same request on the other app without you needing to do any sort of reverse-proxy magic.

Demo

You can verify it here:

• Replay app: https://fly-replay-app.fly.dev
• Replay app rerouting to blog: https://fly-replay-app.fly.dev/blog

Notes

• The blog app doesn't have IP public addresses since it's going to be routed from fly-replay-app.
• Fly-Replay won't change the /path on the URL so our blog must handle requests that start with /blog* too.

Docs

• Dynamic Request Routing