Express Proxy Requests for Local and Remote Service Parity

express-assets-storage-proxy.ts

// High availability apps require that no distinction be made between local and remote services.
// Attached resources should be accessed by environment variables,
// and in doing so allow you to swap out one attached resource for another.

// Let's setup a reverse proxy that directs image path requests and routes them through a defined server URL.
// By doing so, we decouple server requests for images which allows for easy switching
// from locally served image assets to a CDN by simply updating an environment variable.

import * as express from 'express'
import * as proxy from 'express-http-proxy'
import { join } from 'path'

let proxyBaseImageUrl

if (process.env.BASE_IMAGE_URL) {
	proxyBaseImageUrl = proxy(process.env.BASE_IMAGE_URL, {
		proxyReqPathResolver(req) {
			return process.env.BASE_IMAGE_URL + req.path
		},
	})
} else {
	proxyBaseImageUrl = express.static(join(__dirname, 'public/images'))
}

const app = express()

app.use('/images', proxyBaseImageUrl)