Error in heartbeat function

When using the launcher, we encounter an error in the heartbeat function

[20:01:01] TypeError: Cannot read property 'title' of undefined
    at Timeout._onTimeout (/home/travis/build/ampproject/amphtml/node_modules/karma-sauce-launcher/dist/launcher/launcher.js:36:20)
    at listOnTimeout (internal/timers.js:549:17)
    at processTimers (internal/timers.js:492:7)

Relevant snippet:

  // Heartbeat function to keep alive sessions on Sauce Labs via webdriver JSON wire calls
  const heartbeat = () => {
    pendingHeartBeat = setTimeout( (driver) => {
      log.debug('Heartbeat to Sauce Labs (%s) - fetching title', browserName)

      driver.title()
        .then(null, (err) => {
          log.error('Heartbeat to %s failed\n  %s', browserName, formatSauceError(err))

          clearTimeout(pendingHeartBeat)
          return this._done('failure')
      });

      heartbeat()
      }, 60000);
}

I’m not sure how driver could get set; I’m not familiar with setTimeout providing any arguments to its callback. Should this be trying to read from connectedDrivers or something similar?

/cc @joshmgrant

[joshmgrant]

@rcebulko not yet but I’m going to see if I can get something together in the next few days

[triadiprabowo]

I am experiencing same problem in version 4.1.2