Crash when using with fastify-http-proxy websockets

[msundvick]

Prerequisites

• [X] I have written a descriptive issue title
• [X] I have searched existing issues to ensure the bug has not already been reported

Fastify version

4.20.0

Plugin version

8.2.0

Node.js version

16.18.1

Operating system

Linux

Operating system version (i.e. 20.04, 11.3, 10)

22.04

Description

Adding both a websocket endpoint and a proxy to a websocket endpoint doesn't work. Error seems mostly the same as https://github.com/fastify/fastify-websocket/issues/249. If I switch around the order I add the proxy and websocket endpoint, I can get it to log the error and continue instead of just crashing, but still doesn't work.

Error [ERR_INTERNAL_ASSERTION]: This is caused by either a bug in Node.js or incorrect usage of Node.js internals.
Please open an issue with this stack trace at https://github.com/nodejs/node/issues

    at new NodeError (node:internal/errors:387:5)
    at assert (node:internal/assert:14:11)
    at ServerResponse.assignSocket (node:_http_server:280:3)
    at Server.<anonymous> (/home/msundvick/Documents/simulator/sgpsim/node_modules/@fastify/http-proxy/index.js:91:19)
    at Server.emit (node:events:525:35)
    at Server.emit (node:domain:489:12)
    at onParserExecuteCommon (node:_http_server:772:14)
    at onParserExecute (node:_http_server:686:3) {
  code: 'ERR_INTERNAL_ASSERTION'
}

Steps to Reproduce

  const proxy = await import("@fastify/http-proxy");
  if (backend) {
    await fastify.register(proxy, {
      upstream: backend,
      prefix: "/api", // optional
      http2: false, // optional
      websocket: true,
    });
  }

  await fastify.register(require("@fastify/websocket"));
  fastify.register(async function (fastify) {
    fastify.get("/api2", { websocket: true }, (connection, req) => {});
  });

Expected Behavior

No response

[mcollina]

I've transfered this to fastify-http-proxy because that's where the core of the issue is.

[mcollina]

Unfortunately @fastify/websocket and @fastify/http-proxy are incompatible. Long story short, they "plug" into the same event listener on the http server and must do different things to do their job.

Some reconciliation might be possible long term, but it's a significant amount of work that I do not have the bandwidth to take on. If anybody is willing, I would love to see this investigated and fixed.

https://github.com/fastify/fastify-websocket/issues/249 was correctly fixed there, the problem relies on this module now.