Re: Emacs Cloud (coverage and killed groups)

[Ted Zlatanov <tzz@lifelogs.com>]

On Thu, 06 Feb 2014 18:49:09 -0800 Lars Ingebrigtsen <larsi@gnus.org> wrote: 

LI> I had originally thought of the Cloud stuff being totally symmetrical,
LI> but perhaps that's not the best approach here.

LI> That is, at home I have a Gnus setup that contains a gazillion servers,
LI> and some of them are local, like nnml ones.  These obviously shouldn't
LI> be replicated to other instances.  Fine.

LI> But what happens to the topic topology?  If we push out newsrc data that
LI> contains only these replicated groups initially (and I think that's the
LI> right solution), what happens if we move a group from one topic to
LI> another in one of the other instances?  We can't just do a full new dump
LI> of the topology back to the "home" instance, because it no longer
LI> contains all the groups...

I would have a special "cloud" topic at the top level.  Or a "cloudify"
per-group property (not per server!)

Groups that have "cloudify" are then synchronized, together with their
topology position.  So the group would know it's under topic G, and if G
doesn't exist, it will be created.  Changing the topology of a group is
a configuration change like any other.  Again, this is *per group* so
you don't have a global topology map with cloudified groups.

I think inverting the gnus-cloud configuration from
global-descending-to-local to per-group is key here, but it does
complicate the interaction with the Gnus state.

LI> So I'm now thinking we have to have a strict division between one "home"
LI> instance that contains everything, and that can do full chunk dumps.
LI> And then all the other instances would just log updates

That's good.  But it should simply be a choice of "this instance
subscribes to cloudified groups X, Y, and 'gmane.*'" instead of making
such special cases.

LI> The main problem, though, is that if you're not on your home instance
LI> for months, the number of incremental chunks might get pretty ... huge.

LI> But that may not actually be much of a problem.

Nowadays, probably not.  Fast connections are pretty common.  Even a 3G
connection is quite fast (the lowest network speed I would expect from
our user base).

Ted