Reducing data latency: accelerating the 'shutdown' main ping

Alessio Placitelli aplacitelli at mozilla.com
Mon May 22 14:03:27 UTC 2017


*tl;dr*
The 'main-ping
<https://gecko.readthedocs.io/en/latest/toolkit/components/telemetry/telemetry/data/main-ping.html>'
contains the bulk of our probes and measurements.
The 'main-ping' with reason 'shutdown' makes up for about 80% of all the
main pings <https://bugzilla.mozilla.org/show_bug.cgi?id=1336360#c24>.

Thanks to Ping Sender
<https://gecko.readthedocs.io/en/latest/toolkit/components/telemetry/telemetry/internals/pingsender.html>
we are receiving most of them within minutes from the browser shutdown.


*How did we do it?*
Starting from the second browsing session, when the browser shuts down, we
spawn a separate process (Ping Sender!) with the sole responsibility of
transmitting the 'shutdown' main-ping, instead of waiting for the browser
to be restarted by the user.

The analysis
<https://github.com/mozilla/mozilla-reports/blob/master/projects/main_ping_delays_pingsender.kp/knowledge.md#submission-delay>
of the data coming from Nightly looks very promising: 85% of the 'shutdown'
pings are received as soon as generated, versus 35% within the first hour
when no pingsender is used.


*Why are we starting from the second session?*
To prevent 'bot-profiles'/'bot-machines' just creating a single profile and
then deleting it after the first session to skew our analyses.


*Is it complete?*
This feature is functionally complete, we're in the process of smoothing
some rough edges, and have bugs filed for that (on track for 55).

- Bug 1363345: Don't use the pingsender when Firefox closes because the OS
is shutting down
- Bug 1364673: Unwanted mouse throbber appears a few seconds after exiting
Nightly when telemetry is enabled
- Bug 1365978: Validate sending shutdown pings using the PingSender [Beta]

If anything seems off and you think it's due to the pingsender, please file
a bug against 1343277.

Kudos to everyone involved in this!

Alessio
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