[Bro-Dev] [Bro-Commits] [git/broker] topic/actor-system: Add broker::bro::RelayEvent message type. (ce86016)

[Robin Sommer]

On Thu, Dec 14, 2017 at 15:27 -0600, you wrote:

> or proxy/data to all other proxy/data nodes (within these classes,
> nodes aren't connected with each other) was frequent enough to warrant
> putting in a single, simple function call like this.

Yeah, though then I'd actually say it's worth keeping multi-hop
topologies in mind at least. We don't need to fully solve this right
now; nobody really knows yet how topologies may end up looking in the
future. But a good rule of thumb I think is considering that generally
nodes may not be reachable directly, but only through other Broker
hops, and that Broker takes care of the routing to get messages there
as long as topic subscriptions are set up appropiately. Seems that's
actually what we have here already for some nodes. Could we use
Broker-level routing here to get connectivity between the nodes that
aren't directly connected?

> At least currently, Bro has the forwarding capability of Broker turned
> off.  IIRC, it was very easy to unintentionally create routing loops
> when it was turned on and when I asked about it, no one gave any
> justification or use-case for it, thus it got turned off.

It's off because we indeed don't really have understood yet how to use
it. :) But Broker has message TTLs already for detecting loops, and
generally I don't think there's anything preventing us from turning it
on; it should work.

That all said, the priority right now is on getting a basic cluster to
work, so no problem doing the relaying as you have it now if that gets
us there the quickest. Let's just keep thinking about how such
mechanisms will look in the future in other topologies, so that we
don't back us into a corner (and I hear your of course: to really do
that, we need to understand better where we want to get to).

Robin

-- 
Robin Sommer * ICSI/LBNL * robin at icir.org * www.icir.org/robin