Make http.OutgoingMessage._writeRaw public

[evert]

Is your feature request related to a problem? Please describe.

I am trying to return HTTP informational statuses to the client. In particular 100, 102, 103 but I would also like to open the door to being able to support future informational status codes.

Both 100 and 102 have a dedicated method:

• HttpServerResponse.sendContinue for 100 and
• HttpServerResponse.sendProcessing for 102.

It would be possible to add another function like it (sendEarlyHints), but it seems a little silly given that these informational statuses more or less follow the same structure.

The http2 library solves this with the additionalHeaders function. To illustrate, this is how I send any informational status using http2:

const otherHeaders = { };
const status = 103;

stream.additionalHeaders({
   ':status': status,
  ...otherHeaders
});

This is how I do it for the HTTP1 api:

const otherHeaders = { };
const status = 103;
const rawHeaders = [];
  for (const headerName of Object.keys(outHeaders)) {
    const headerValue = outHeaders[headerName];
    if (Array.isArray(headerValue)) {
      for (const headerVal of headerValue) {
        rawHeaders.push(`${headerName}: ${headerVal}\r\n`);
      }
    } else {
      rawHeaders.push(`${headerName}: ${headerValue}\r\n`);
    }
}

const writeRaw = promisify(res._writeRaw.bind(this.inner));
const message = `HTTP/1.1 ${status} ${http.STATUS_CODES[status]}\r\n${rawHeaders.join('')}\r\n`;
await writeRaw(message, 'ascii');

The problem here is that I'm using res._writeRaw, an undocumented 'private' feature. I would like to not have to rely on this, but as far as I can tell, it's the only 'sane' way.

Describe the solution you'd like

Make _writeRaw a documented, supported feature OR supply a reasonable API for returning any 1xx status header.

Describe alternatives you've considered

As far as I know there's no real alternative.

[addaleax]

@nodejs/http

[apapirovski]

I am reasonably certain this is kinda possible with writeHead, e.g., res.writeHead(103); but it has downsides (extra headers, doesn't flush immediately, etc.). It would probably make sense to expose an API that actually did the expected thing, similar to the http2 version.

[evert]

I believe writeHead may only be called once. One implication of informational statuses, is that their never the 'final' status. There's always one that follows. I think this is also why both sendContinue and sendProcessing under the hood actually just call _writeRaw.

[evert]

I'm actually happy and comfortable to contribute this change as well.

[apapirovski]

@evert Yeah, you're right. I was confused by the fact that we had some extra handling for informational statuses inside writeHead. That code probably needs to be refactored, honestly.

I'm referring to this line:

node/lib/_http_server.js

Line 251 in 0740394

(statusCode >= 100 && statusCode <= 199)) {

In terms of an API, it probably should be possible to call writeHead with informational status codes and have it to do the expected thing.

[Trott]

Is anyone working on this? Should it get a stalled label and moved to https://github.com/nodejs/node/projects/13? /cc @refack

[refack]

My cut off was six months, but if there's indication no one is picking this up, it could go in the backlog.

[Trott]

Closing as stalled. Will add to feature requests backlog at https://github.com/nodejs/node/projects/13.