1893243 - Handle recovery of backup that was created from an older than 1 ESR in the past

Status: NEW

(Firefox :: Profile Backup, task, P3)

Description

[Mike Conley (:mconley) (:⚙️)]

This is projecting a bit further into the future, but one can imagine a world where a user in 2035 wants to recover from a profile created in 2024. In the intervening years, it's possible that the formatting and schemas of various datastores within the backup are no longer compatible with the 2035 instance of the application.

A naive thing to do for us is to check if the backup was created from a version of the application more than 1 ESR old. Let's call the version that the backup was created on X. We could provide a link to download and install the first new ESR released after X, which should still be compatible (since users will have needed to have upgraded from the ESR prior to X to the ESR after X).

The problem, however, is that if the backup is sufficiently old, we could get into an issue where the next ESR after X is in such a state that it no longer functions on the hardware that the user has. In that case, we might need to release tools that forward-migrate the data stores from version X to the modern reckoning.

This is all fairly fluffy and future-thinking, but it's the sort of thing we're going to have to grapple with if we want to support backups for the long-term.