>Regarding "minority of cases", is this based on a quantitative
>estimate? I would be interested to learn more about this.Yes, this is race condition, subscribing to onload is an anti-pattern as it is not a promise, but more often than not it would have worked fine.
You can see that on the data too (which might make more sense to you)  the fix went live on 2017-09-28 and you can see no noticeable increase on NavigationTiming events:
https://grafana.wikimedia.org/dashboard-solo/db/eventlogging-schema?orgId=1&var-schema=NavigationTiming&from=1505250864328&to=1507842864328&panelId=9


In the Popup case you might have hit this race condition perhaps more often (that can be), it will be easy enough to verify when you set up your next experiment. 

Thanks,

Nuria



On Thu, Oct 12, 2017 at 9:33 PM, Tilman Bayer <tbayer@wikimedia.org> wrote:
Regarding "minority of cases", is this based on a quantitative
estimate? I would be interested to learn more about this.

In any case though, Nuria is correct in pointing out that it's less
than 100% - it's certainly possible that events are being sent again
later in the session (this happened e.g. when I reproduced the bug
here: https://phabricator.wikimedia.org/T175918#3612580 , and is also
evident in data e.g. from the previous Popups experiments).

On Thu, Oct 12, 2017 at 2:14 PM, Nuria Ruiz <nuria@wikimedia.org> wrote:
> Please have in mind that hiting this bug is a race condition and it is hit
> in a minority of cases, not all times. The essence of the bug has to do with
> the subscription to the "load" event. In some instances the event had
> already happened by the time the EL code was loaded.
>
> Thanks,
>
> Nuria
>
>
>
>
>
> On Thu, Oct 12, 2017 at 7:35 AM, Dan Andreescu <dandreescu@wikimedia.org>
> wrote:
>>
>> Thanks for the post, this bug will definitely bias any data people got
>> with mw.track.  If the data is found to be so broken as to be useless,
>> should we delete it up through the date the fix goes live?  Asking people
>> who use mw.track, not Sam
>>
>> On Thu, Oct 12, 2017 at 6:41 AM, Sam Smith <samsmith@wikimedia.org> wrote:
>>>
>>> o/
>>>
>>> Prior to Thursday, 28th September, if your client-side EventLogging
>>> instrumentation logged event via mw.track, then only events tracked
>>> during the first pageview of a user's session were logged.
>>>
>>> Now, technically, the events weren't ignored or dropped. Instead, the
>>> subscriber for the "event" topic was never subscribed when the module
>>> was loaded from the ResourceLoader's cache and so events published on
>>> that topic simply weren't received and logged.
>>>
>>> This bug was discovered while testing some instrumentation maintained
>>> by Readers Web [0] and independently by Timo Tijhof, who submitted the
>>> ideal fix [1] promptly.
>>>
>>> -Sam
>>>
>>> [0] https://phabricator.wikimedia.org/T175918
>>> [1] https://gerrit.wikimedia.org/r/#/c/378804/
>>>
>>> ---
>>> Engineering Manager
>>> Readers
>>>
>>> Timezone: BST (UTC+1)
>>> IRC (Freenode): phuedx
>>>
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>>
>>
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--
Tilman Bayer
Senior Analyst
Wikimedia Foundation
IRC (Freenode): HaeB

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