This is a meta ticket tracking making Nimbus experiments work in Firefox background tasks. A cursory examination of the Nimbus code shows that it's almost certainly possible to have Nimbus experiments work in said background tasks, but there are a number of accommodations required. This is a dumping place to collect and discuss these issues.

The most obvious issue is that background tasks run in temporary/ephemeral profiles. Clearly this does not allow for Nimbus to persist enrolment information, to allow opt-outs as usual, etc. And clearly the ASRouterTargeting.Environment piece needs to be modified (or perhaps replaced with a serialization of the targeting from the default profile.)

We might want the ability to target background task mode (or a specific background task name) specifically, since there's a risk that unexpected experimental code could run in an unexpected context. But perhaps we can simply have certain Nimbus features used in background tasks and most features simply not used at all.

(Taking a best guess at priority/severity - adjust as needed.)

(In reply to bhearsum@mozilla.com (:bhearsum) from comment #1)

(Taking a best guess at priority/severity - adjust as needed.)

I'm going to drive this down, 'cuz it's not clear that using Nimbus is the best approach across all axes. That is, we might build something special to background tasks, or even to just background update, etc.

This work will depend on the active effort to report Nimbus telemetry with Glean (in addition to legacy telemetry), since background tasks do not support legacy telemetry. That work is tracked by https://mozilla-hub.atlassian.net/browse/EXP-2423.

Part of this work will be running a telemetry-only A/A test to be confident that we are actually targeting, bucketing, etc correctly with Nimbus in background tasks, that the telemetry pipeline is flowing, that automated analysis is running, etc.