How to support HTTP 103 Early Hints?

[zizifn]

hi,

WIth Chrome 103, the HTTP 103 Early Hints is in release build. But how to support this in expressjs? Thanks!!

https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/103
https://developer.chrome.com/blog/new-in-chrome-103/

[dougwilson]

The Node.js server Express.js is built on does not yet support 103, only 100, 101 and 102. You'll want to petition Node.js to add 103 support to their HTTP server so it can be made available in Express.js and other frameworks built on Node.js HTTP.

[fishcharlie]

@dougwilson Node.js looks to have merged this nodejs/node#44180. However, I don't think it has been included in a Node.js release (yet).

What are the odds this can be revisited/reopened?

Obviously this leads to a lot more questions. What is Express.js's policy about new Node.js changes that aren't back-ported? Express.js currently supports Node.js >=0.10.0, and I'd be shocked if that PR gets back-ported that far. How many Node.js versions should this be included in before Express.js supports this feature? etc.

[dougwilson]

Hi @fishcharlie I'm not sure what needs to be re-opened? Until that lands, it isn't possible to send the 103 response in Express.js since Node.js does not support it. Once that PR lands in Node.js, the API is automatically available in Express.js when used with that Node.js version. But Express.js cannot backport things to old Node.js versions, only the Node.js project can... Please let me know if I'm missing something.

[fishcharlie]

@dougwilson Thanks so much for the reply.

Everything (minus one part) you said makes sense and I agree with all of it.

Once that PR lands in Node.js, the API is automatically available in Express.js when used with that Node.js version

This is the part I'm slightly confused about. I was under the impression that Express.js was basically a wrapper around the Node.js HTTP package. Therefore, wouldn't the wrapper need to be updated to support that new method?

Methods such as res.set don't exist within the native HTTP package (I assume it gets mapped to response.setHeader).

So shouldn't Express.js (at some point) add a new method for the writeEarlyHints method that was added in that PR? Similar to how res.set maps to response.setHeader. Something like res.earlyHints that gets mapped to response.writeEarlyHints?

[dougwilson]

No, it's not a wrapper, it is inheritance. Anything on the Node.js response is on the Express.js response, because it's just class inheritance. The Express.js response is just a subclass of the Node.js response. You'll notice you can call res.writeProcessing() and res.writeContinue() in your Express.js middleware, yet you won't find those anywhere in the Express.js source code, since nothing needs to be done to add methods from the Node.js classes to the Express.js ones. I hope that helps.