http2: trailers or response to be emitted?

[szmarczak]

Version

v17.3.0

Platform

Linux pop-os 5.15.5-76051505-generic #202111250933~1638201579~21.04~09f1aa7-Ubuntu SMP Tue Nov 30 02: x86_64 x86_64 x86_64 GNU/Linux

Subsystem

http2

What steps will reproduce the bug?

const http2 = require('http2');

const server = http2.createServer((request, response) => {
 response.writeContinue();
 response.end(); // Make it end('') and it emits `response` instead
});

server.listen(() => {
 const { port } = server.address();

 const session = http2.connect(`http://localhost:${port}`);
 const request = session.request({
 ':path': '/',
 ':method': 'GET',
 });

 request.on('response', (headers) => {
 console.log('got response', headers);
 });

 request.on('headers', () => {
 console.log('got headers');
 });

 request.on('trailers', (trailers) => {
 console.log('got trailers', trailers);
 });

 request.end();
 request.resume();

 request.on('end', () => {
 session.close();
 server.close();
 });
});

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

Always.

What is the expected behavior?

got headers
got response [Object: null prototype] {
 ':status': 200,
 date: 'Mon, 20 Dec 2021 08:27:48 GMT',
 [Symbol(nodejs.http2.sensitiveHeaders)]: []
}

What do you see instead?

got headers
+got trailers [Object: null prototype] {
 ':status': 200,
 date: 'Mon, 20 Dec 2021 08:27:48 GMT',
 [Symbol(nodejs.http2.sensitiveHeaders)]: []
}

Additional information

I'm not sure if this is the expected behavior. HTTP/1 for comparison (trailers are empty):

 const http = require('http');

 const server = http.createServer((request, response) => {
 response.writeContinue();
 response.end();
 });

 server.listen(() => {
 const { port } = server.address();

 const request = http.get(`http://localhost:${port}`, response => {
 response.resume();

 response.on('end', () => {
 console.log(response.trailers, response.rawTrailers);

 server.close();
 });
 });

 request.on('information', () => {
 console.log('information');
 });
 });

information
{} []

[szmarczak]

Relevant RFC: https://datatracker.ietf.org/doc/html/rfc7540#section-8.1

[szmarczak]

Wireshark

trailers event:

response event:

[szmarczak]

The last frame in the sequence bears an END_STREAM flag, noting that
a HEADERS frame bearing the END_STREAM flag can be followed by
CONTINUATION frames that carry any remaining portions of the header
block.

Trailing header fields are carried in a header block that also
terminates the stream. Such a header block is a sequence starting
with a HEADERS frame, followed by zero or more CONTINUATION frames,
where the HEADERS frame bears an END_STREAM flag.

👍

[szmarczak]

Following: then

const http2 = require('http2');

const server = http2.createServer((request, response) => {
 response.end(); // just empty end, nothing else
});

server.listen(() => {
 const { port } = server.address();

 const session = http2.connect(`http://localhost:${port}`);
 const request = session.request({
 ':path': '/',
 ':method': 'GET',
 });

 request.on('response', (headers) => {
 console.log('got response', headers);
 });

 request.on('headers', () => {
 console.log('got headers');
 });

 request.on('trailers', (trailers) => {
 console.log('got trailers', trailers);
 });

 request.end();
 request.resume();

 request.on('end', () => {
 session.close();
 server.close();
 });
});

got response [Object: null prototype] {
 ':status': 200,
 date: 'Mon, 20 Dec 2021 09:47:15 GMT',
 [Symbol(nodejs.http2.sensitiveHeaders)]: []
}

I think it should emit trailers instead of response.

Wireshark

[MoonBall]

I think it should emit trailers instead of response.

I think HTTP/2 should be consistent with HTTP/1 behavior. About the above case, they shouldn't emit trailers event.

[szmarczak]

@MoonBall Please note that in the original issue it emits trailers instead of response. I'd prefer consistent behavior over making it look like HTTP/1.

[MoonBall]

In the original issue I think it should emit response. I would like to dig into it

[aduh95]

Duplicate of #38258