Prerequisites

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

Fastify version

4.25.2

Plugin version

No response

Node.js version

20.10

Operating system

Windows

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

11

Description

I make a fetch call on my Fastify server and I want to return the response from that fetch call as the response of my Fastify route as a stream.

I thought this would work since Fastify has stream docs (https://fastify.dev/docs/latest/Reference/Reply/#streams), but it does not.

Steps to Reproduce

Clone this github repo: https://github.com/TJBlackman/fastify-stream-test

Install dependencies and run the project:

• npm i
• npm run dev

Make requests to the API:

• GET http://localhost:3000/api/json - Works!
• GET http://localhost:3000/api/stream - Does not work :(

For the sake of completeness, here is the demo server file you could copy/paste if you want.

const fastify = require("fastify")({ logger: true });

// return JSON from SWAPI - works!
fastify.get("/api/json", async (request, reply) => {
  const response = await fetch("https://swapi.dev/api/people/1/");
  const json = await response.json();
  return reply.send(json);
});

// return stream from SWAPI - doesn't work
fastify.get("/api/stream", async (request, reply) => {
  const response = await fetch("https://swapi.dev/api/people/1/");
  return reply.send(response.body);
});

fastify.listen({ port: 3000 }, (err) => {
  if (err) {
    fastify.log.error(err);
    process.exit(1);
  }
});

Expected Behavior

The streamed response should be the same as the JSON response.