Add Fission as a "compare by" option

[cpeterso]

The Firefox Fission team would like to add a "Fission" option to telemetry.mozilla.org's "compare by" drop-down menu.

With Fission enabled, Firefox will create many more content processes than before, which will likely impact memory usage and performance. I'm working with Data Science to create a real dashboard for Fission release readiness metrics, but Fission engineers would also like to do ad hoc comparisons of Fission vs non-Fission for any telemetry probe.

Users with Fission enabled have the fission.autostart pref set. Is that pref value adequate to partition Fission and non-Fission users on telemetry.mozilla.org?

For now, Fission is only relevant for the Firefox Nightly channel, but it might start riding the trains to Beta in 2020 Q2.

[fbertsch]

Great, that should be all we need, since that value is already sent through telemetry.

[fbertsch]

cc @emtwo for GLAM

[tdsmith]

I left a comment on the bug that added this to the telemetry environment, but heads up that the reported value only reflects whether fission.autostart has a value on the user branch. While fission.autostart is off by default, the reported values will be either true (Fission enabled) or missing (Fission disabled). Someday, when Firefox builds start shipping with fission.autostart set to true on the default branch, the reported values from those builds will be either false (Fission disabled) or missing (Fission enabled).

i.e. understanding whether a client has Fission enabled based on this probe will, in the future, require additional knowledge about the build that's sending telemetry.

[cpeterso]

heads up that the reported value only reflects whether fission.autostart has a value on the user branch. While fission.autostart is off by default, the reported values will be either true (Fission enabled) or missing (Fission disabled). Someday, when Firefox builds start shipping with fission.autostart set to true on the default branch, the reported values from those builds will be either false (Fission disabled) or missing (Fission enabled).

@tdsmith - Should we change how the Fission pref is initialized or recorded to make the pref ping processing easier when comparing Fission vs non-Fission?

https://searchfox.org/mozilla-central/rev/04d8e7629354bab9e6a285183e763410860c5006/toolkit/components/telemetry/app/TelemetryEnvironment.jsm#276

[tdsmith]

If you're ready to start reporting this value in telemetry for all users, you can use RECORD_DEFAULTPREF_VALUE instead of RECORD_PREF_VALUE; https://searchfox.org/mozilla-central/rev/04d8e7629354bab9e6a285183e763410860c5006/toolkit/components/telemetry/app/TelemetryEnvironment.jsm#191-193.

[cpeterso]

Thanks. I'll talk with the Fission engineers. I don't see any harm in reporting this pref value for all users now. The pref is locked so the feature itself can only be activated in the Firefox Nightly channel.

[cpeterso]

I filed Fission bug https://bugzilla.mozilla.org/show_bug.cgi?id=1600818.

[cpeterso]

I filed Fission bug https://bugzilla.mozilla.org/show_bug.cgi?id=1600818.

This bug has been fixed in Firefox 77 Nightly. The fission.autostart pref value is now being recorded using RECORD_DEFAULTPREF_VALUE, so the pref value will always be reported, even when it is the default value (currently false). This should make writing telemetry queries more future-proof when we eventually flip the pref default to true.

@tdsmith - What are the next steps for requesting that a "Fission vs non-Fission" option be added to TMO's "compare by" menu?

[tdsmith]

AIUI that's on GLAM's roadmap, which is the tool that will replace Measurement Dashboard; @rafrombrc is probably the best contact if you have questions about that.

[cpeterso]

AIUI that's on GLAM's roadmap, which is the tool that will replace Measurement Dashboard; @rafrombrc is probably the best contact if you have questions about that.

@rafrombrc - Is new telemetry browsing UI development focused on GLAM and not TMO? Do you have a demo or timeline you can share?