1128491 - Make important Telemetry session measurements reset per subsession

Status: RESOLVED FIXED

(Toolkit :: Telemetry, defect, P4)

Description

[Georg Fritzsche [:gfritzsche]]

Per the discussion on the FHR/Telemetry unification concerns [0] we want to go with client-side submission of both "reset per subsession" and "old style telemetry" histograms.

Bug 1127914 duplicates the histograms, this will take care of the measurements implemented in JS in TelemetrySession.jsm.

0:"Suggestions for the new unified FHR/Telemetry/Experiment ping", https://mail.mozilla.org/pipermail/fhr-dev/2015-January/thread.html#382

Comment 1

[Georg Fritzsche [:gfritzsche]]

Ok, i'm not entirely sure on the scope of this bug.

Benjamin, Vladan, do you have requirements on which JS implemented measurements we need to reset for the subsession data?
We have an overview of the main ping data here:
https://ci.mozilla.org/job/mozilla-central-docs/Tree_Documentation/toolkit/components/telemetry/telemetry/main-ping.html

Histograms (plain and keyed) are duplicated in bug 1127914 already.

Comment 2

[Vladan Djeric (:vladan)]

- Definitely reset simpleMeasurements.activeTicks when you start a new subsession. Talk to Avi about that.
- sm.debuggerAttached, sm.maximalConcurrentThreads and sm.js (setProto + customIter) should probably get reset, but these are not being used for much at the moment, and I'd be ok with not resetting them.
- Eventually, we should reset almost all Telemetry measurements when we start a new subsession.. BHR, slowSQL, chromehangs, main-thread I/O. Also future work
- The startup measurements technically only belong in the first subsession, but there's no harm (and there is some benefit) to not resetting them
- Some measurements should never be reset, e.g. UITelemetry
- For the time-being, resetting the histograms is sufficient

- You might need to ask someone else what to do with the FHR probes when a new subsession begins

Comment 3

[Benjamin Smedberg]

For now, we don't need to divide BHR, slowSQL, chromehangs, UITelemetry, or main-thread IO, and we can submit those only with the last subsession.

In the future we'll want to divide BHR, slowSQL, chromehangs, and main-thread IO, but I don't know what we want to do with UITelemetry (I want to spend some time understanding that mechanism more thoroughly anyway, from a privacy perspective).

Comment 4

[Georg Fritzsche [:gfritzsche]]

Thanks, this definitely doesn't need work for phase 2 then.

Comment 5

[Georg Fritzsche [:gfritzsche]]

From what i gather here, we should be good with duplicating simpleMeasurements.activeTicks for subsessions for now.
Moved that to bug 1137222 and this bug to a later phase.

Comment 6

[Thomas Huelbert]

task is to break this bug into discrete items, then size those for q4

Comment 7

[Jan-Erik Rediger [:janerik]]

With the saved-session ping gone we know that all relevant stuff is already reset on subsessions.