Streaming responses

[jmandel]

Is there some mechanism to return a stream? Say I want to write a function that calls fetch and returns the fetch's response body, without accumulating the full body in memory?

Sorry if this is something obvious; from the docs and types.ts I'm having trouble seeing how this is covered.

[bogeychan]

Hi 👋

this should do it, see:

• Fetch response body streaming
• Bun.serve() streaming improvements

import { Elysia } from 'elysia';

const app = new Elysia()
  .get('/', () => fetch('https://github.com/elysiajs/elysia/issues/250'))
  .listen(3000);

console.log(`Listening on http://${app.server!.hostname}:${app.server!.port}`);

Or with custom Stream:

app.get(
  '/',
  () =>
    new Response(
      new ReadableStream({
        pull(controller) {
          controller.enqueue('Hello world!');

          controller.close();
        }
      })
    )
);

[jmandel]

Thanks so much! It might be worth including a link out to the definition of the response object in the documentation at https://elysiajs.com/concept/handler.html#response ; I did not realize this would be a standard like https://developer.mozilla.org/en-US/docs/Web/API/Response or similar.

[emilianomon]

Any tips on how to document the response?

I am using the Swagger plugin and it does not seem to exist a way to do it using Typebox.

[crishoj]

@emilianomon, you mean this? → https://elysiajs.com/patterns/creating-documentation.html#route-definitions

[emilianomon]

Since there is no way to relate the returning type of the streaming write call with the actual handler method, the question was wrongfully posed.

Is there a way to inject a streaming helper that actually takes de response validation type into consideration?

My end goal is to have a typeface streaming emit.

[SaltyAom]

Closing with the introduction of Stream plugin.

[emilianomon]

Perfect. Just for another round of clarification, I thought of something like the following:

import Elysia, { t } from 'elysia';
import { stream } from '@elysiajs/stream';

const handler = new Elysia();

handler
use(stream)
.post('/stream', ({ stream }) => {

  stream.send({
    validatedAttribute: true, // This should be validated and typesafe.
  });

  return stream;
}, {
  response: t.Object({
      validatedAttribute: t.Boolean(),
  }),
});

export { handler as streamHandler };

Or even a custom stream validation like:

// ...
}, {
  stream: t.Object({
      validatedAttribute: t.Boolean(),
  }),
});
// ...

A stream helper injection that takes into consideration the response validation seems to me like a great addition!

Does it make sense @SaltyAom?