Why http2session.socket.bufferSize is always zero?

[micooz]

• Version: v10.4.1
• Platform: macOS 10.13.5
• Subsystem: net,http2

I encountered a problem that I couldn't get expected bufferSize from http2session, http2session.socket.bufferSize is always zero.

Reproduce Code

I write a test similar to test-net-buffersize.js:

const assert = require('assert');
const http2 = require('http2');

const server = http2.createServer();

server.listen(0, () => {
  const session = http2.connect(`http://localhost:${server.address().port}`);
  const stream = session.request({ ':path': '/' }, { endStream: false });

  for (let i = 1; i < 10; i++) {
    assert(stream.writable);
    stream.write('a');
    assert.strictEqual(session.socket.bufferSize, i); // AssertionError
  }

  stream.close();
});

Is it correct way to obtain bufferSize from http2 session? I need this value to throttle uploads like net.Socket do.

[jasnell]

This is due to the special way that http2 sessions interact with the socket at the native (c++) layer rather than the javascript layer. The socket object's js interface is not used directly, and therefore the bufferSize is not set. We can investigate a way of enabling that.

[jasnell]

@addaleax ... do you have any thoughts on how we could make bufferSize work on a socket bound to an http2session?

[oyyd]

According to the net module, bufferSize is:

node/lib/net.js

Line 518 in deaddd2

return this[kLastWriteQueueSize] + this.writableLength;

As Http2Session and Http2Stream have internally maintained writeQueueSize which is actually kLastWriteQueueSize, I think, maybe we can make bufferSize work on http2 module itself.

[apapirovski]

The PR for this has landed so I believe we can close this.