Hi All,
Here's a quick take on how version-negotiation might look in practice.
I'm deliberately proposing a very blunt and inelegant instrument, in an
attempt to surface what our minimal needs really are.
Version negotiation is handled at the Firefox Accounts layer, via an API
that lets you list and inspect all the devices attached to the account.
You query the endpoint, and get a set of devices with names and version
strings:
GET /account/devices
{
"<device-uuid>": {"name": "Ryan's Laptop", "version", "A.B.X"},
"<device-uuid>": {"name": "Ryan's Phone", "version", "A.B.Y"},
}
Each device is responsible for registering itself when it connects to
the account, and for keeping its details up-to-date.
We then manage a future protocol or format update as follows:
1) We ship FxAccounts + SyncX.Y, without solving all the big thorny
storage problems that we'd really like to solve.
2) There's a user-visible flag-day, during which they manually
transfer all their devices over the Firefox Accounts.
3) Sometime later we ship FxAccounts + TreeSync, and there is
much rejoicing.
4) TreeSync enabled devices check their peers through the device
management api, and delay upgrading to TreeSync until they are
all at some minimal version that's capable of supporting it.
5) The user eventually upgrades all their devices, and their data
is transparently migrated into TreeSync without another flag-day.
6) Many years from now, we can finally turn off the original storage
servers.
It's a blunt instrument, but ISTM that this would work OK.
What I like about putting this in the Firefox Accounts layer, is that it
doesn't block on any other decisions. We could ship this layer on top
of Sync1.1, or Sync2.0, or CouchDB, or whatever happens to be ready at
the time, and we'd have a way to dig ourselves out of whatever mess
we've made (if any!)
Thoughts?
More generally: if this really is the only other
absolutely-must-have-before-flag-day feature, then let's get it nailed
down ASAP.
Cheers,
Ryan
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