695134 - Clients should advertise feature set

Status: NEW

(Firefox :: Sync, defect)

Description

[Gregory Szorc [:gps]]

Clients should self-advertise their supported features.

Currently, the Clients engine doesn't know anything about a remote client other than its name, type (desktop or mobile), and a set of commands destined for that client.

Advertisement of features leads to better user experience. For example, a client could have confidence that the recipient of a (newly-introduced) command actually has the ability to process that command. Currently, this is best effort, with the sender hoping the recipient knows what to do.

Implementation of this feature will likely be a little hacky. We can't just append fields to existing client records because an old client won't know to include these fields when it touches the record. So, we're probably looking at creating additional client records that track features. At some point in the future (the next API version, for example), we could combine these into the unified client record.

Please note that I'm explicitly requesting "feature" advertisement as opposed to "version" advertisement. Per-feature "flags" are more expressive than bland version identifiers.