HTTP responses on Node v14.15.2+ hang

[clshortfuse]

Version: v14.15.2
Platform: Linux ATTIC-PC 5.4.72-microsoft-standard-WSL2 #1 SMP Wed Oct 28 23:40:43 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Subsystem: unsure

What steps will reproduce the bug?

Hosting http1 or http2 streams hang when the response is multi-chunked (large)

How often does it reproduce? Is there a required condition?

Send large responses over HTTP in v14.15.2

What is the expected behavior?

I have a payload for one HTTP request in application that is about 37KB which likely means this is multi-chunked. On v14.9-v14.15.1 there is no issue.

What do you see instead?

On v14.15.2 the response hangs. In total, the application is pushing about 50 requests to a client connection, but it's only this somewhat large one that completely hangs. I'm still troubleshooting to see what's going on.

Additional information

It doesn't matter if it's HTTPS (http1) or HTTP2. Both stall. I'd imagine it's stream related

https://github.com/nodejs/node/blob/master/doc/changelogs/CHANGELOG_V14.md#14.15.2

[clshortfuse]

Found it. Just some typo on my part handling the 'drain' event with a crypto hash stream:

const needsDrain = !hashStream.write(chunk);
if (needsDrain) {
  this.once('drain', () => {
    callback(null, chunk);
  });
} else {
  callback(null, chunk);
}

this.once => hashStream.once. Not a NodeJS bug, but tagging #35941 anyway for posterity. Hash streams might need draining whereas they didn't before.