browser_parent_process_hang_telemetry.js

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/* Any copyright is dedicated to the Public Domain.

   http://creativecommons.org/publicdomain/zero/1.0/ */

"use strict";

/**

 * Check that we record hangs in the parent process in telemetry events.

 * This test would be an xpcshell test except xpcshell does not think

 * it is running e10s (see bug 1568333).

*/

add_task(async function test_browser_hang() {

  // Trip some testing code to ensure we can test this. Sadly, this is a magic

  // number corresponding to code in XPCJSContext.cpp

  await SpecialPowers.pushPrefEnv({

    set: [["dom.max_chrome_script_run_time", 2]],

});

  await SpecialPowers.promiseTimeout(0);

  // Hang for 1.2 seconds.

  let now = Date.now();

  let i = 0;

  info("Start loop");

  while (Date.now() - now < 2500) {

    // The system clock can go backwards. Don't time out the test:

    if (Date.now() - now < 0) {

      info("Yikes, the system clock changed while running this test.");

      now = Date.now();

    i++;

  let duration = (Date.now() - now) / 1000;

  info("Looped " + i + " iterations.");

  let events;

  await TestUtils.waitForCondition(() => {

    events = Services.telemetry.snapshotEvents(

      Ci.nsITelemetry.DATASET_ALL_CHANNELS,

      false

);

    return events.parent?.some(e => e[1] == "slow_script_warning");

  }, "Should find an event after doing this.").catch(e => ok(false, e));

  events = events.parent || [];

  let event = events.find(e => e[1] == "slow_script_warning");

  ok(event, "Should have registered an event.");

  if (event) {

    is(event[3], "browser", "Should register as browser hang.");

    let args = event[5];

    is(args.uri_type, "browser", "Should register browser uri type.");

    Assert.greater(

      duration + 1,

      parseFloat(args.hang_duration),

      "hang duration should not exaggerate."

);

    Assert.less(

      duration - 1,

      parseFloat(args.hang_duration),

      "hang duration should not undersell."

);

});