Suggestions for the new unified FHR/Telemetry/Experiment ping

[Georg Fritzsche]

Hi,

thanks for the write-up. I would like to mention that we should come to a conclusion on this soon if we still want to make 38 as this blocks a big part of the fundamental client changes.

On 24 Jan 2015, at 07:35, Vladan Djeric <vdjeric at mozilla.com> wrote:
> So first off, let me describe my intepretation of the current unification proposal:
> Whenever a new ping is started, all the FHR & Telemetry measurements for the current session will be reset
My assumptions was that we will not reset. There is Telemetry data that is not meaningful when reset, so i could only imagine opt-in for specific probes to be reset (e.g. add a “daily” property to histograms if we need that).
Do we have a good argument for resetting all of them in the first place? Most of your concerns result from that.
> In the new system, Firefox starts collecting a new ping whenever:
> a new Firefox session is started
> a new day has begun (not sure if it's every 24 hours of uptime, or if it's based on local time e.g. midnight local time)
That was a partially open question, midnight local time is what we will do unless there is useful counter arguments.
> There's overhead from sending a new ping for each mid-session environment change
> There's also a small privacy issue with creating ordered, fine-grained reports of user actions, e.g. when a user goes through their add-ons list and disables 5 addons, we report each user action
> Either coalesce successive environment-change pings, or carefully vet which mid-session environment changes generate a new ping
If that is a problem, we can always consider coalescing as an incremental improvement on the current plan.

> I'd like to propose that we implement the following modifications to the FHR/Telemetry v4 document:
> Do not reset Telemetry measurements when a session crosses the 24-hour boundary
> Continue to "reset" Telemetry measurements when we start a new session
> There's no need to reset Telemetry on most environment changes (e.g. amount of memory installed) since those can't happen without a Firefox restart anyway.
> Record mid-session environment changes (add-ons and TelemetryExperiments) in a special section in the ping.
> For each such environment change, document the change in the section and also attach a snapshot of the Telemetry & FHR data at the time of the change
> After the snapshot is saved, reset Telemetry and FHR measurements for the current session. In other words, snapshot & then build up a diff
> For each additional environment change during the same session, just repeat and append to the new section
> Telemetry backend scripts (dashboard, regression detector etc) can just ignore experiment/add-on change pings
What would the snapshots diff against? Diffing going back from the final ping? Also, any diffing client-side adds complexity and potential issue - i’d prefer to avoid that if possible.


Georg
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/fhr-dev/attachments/20150125/7defe492/attachment-0001.html>