backpressure-send.any.js

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// META: script=../../constants.sub.js

// META: script=resources/url-constants.js

// META: global=window,worker

// META: timeout=long

// META: variant=?wss

// META: variant=?wpt_flags=h2

// Allow for this much timer jitter.

const JITTER_ALLOWANCE_MS = 200;

// The amount of buffering a WebSocket connection has is not standardised, but

// it's reasonable to expect that it will not be as large as 8MB.

const MESSAGE_SIZE = 8 * 1024 * 1024;

// In this test, the server WebSocket handler waits 2 seconds, and the browser

// times how long it takes to send the first message.

promise_test(async t => {

  const wss = new WebSocketStream(`${BASEURL}/receive-backpressure`);

  const { writable } = await wss.opened;

  const writer = writable.getWriter();

  const start = performance.now();

  await writer.write(new Uint8Array(MESSAGE_SIZE));

  const elapsed = performance.now() - start;

  assert_greater_than_equal(elapsed, 2000 - JITTER_ALLOWANCE_MS);

}, 'backpressure should be applied to sent messages');