WebSocket proxy handles upgrades regardless prefix

[franzzua]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the issue has not already been raised

Issue

I have app with existing web sockets that should be handled by existing handlers. And when I add proxy with webSockets enabled these old handlers stop working.
Could you describe, why it's necessary to use only one upgrade handler?

[mcollina]

Can you make an example with code so I can understand your full use case?

[dziemdobry]

I have to agree with @franzzua. The plugin indeed does seem to globally listen for every HTTP upgrade without prior verification of whether it owns the endpoint or not. Any WebSocket endpoint registration unrelated to the proxy results in the later client's upgrade corruption.

Example

import Fastify from 'fastify'
import FastifyHttpProxy from '@fastify/http-proxy'
import FastifyWebSocket from '@fastify/websocket'

const server = Fastify()

server.register(FastifyHttpProxy, {
	wsUpstream: 'wss://echo.websocket.org',
	websocket: true,
	prefix: '/echo/',
})

await server.register(FastifyWebSocket)

server.register(async function(fastify) {
	fastify.get('/example', { websocket: true }, (socket, req) => {
		/** This connection gets corrupted during the upgrade. */
	})
})

server.listen({ port: 3000 })

Relevant code

I'm not familiar with the codebase, but this section of the code appears to be the place where it could possibly have the checks missing.

fastify-http-proxy/index.js

Lines 397 to 399 in bd35915

	fastify.server[kWsUpgradeListener] = (rawRequest, socket, head) =>
	handleUpgrade(fastify, rawRequest, socket, head)
	fastify.server.on('upgrade', fastify.server[kWsUpgradeListener])