Danny
On Wed, Jul 14, 2010 at 1:36 AM, Danny Briere <[email protected]> wrote:
> We are looking at applications of PubSubHubbub that are mission
> critical for businesses.
What kinds of applications are you looking at?
> So while businesses will tolerate some level
> of variable delivery delay, they won't tolerate downtime. They are
> used to 100% or near 100% (five nines) type reliability.
>
> Does PubSubHubbub have support for any type of load distribution, load
> balancing, or fault tolerance? For example, what appears to be a
> single hub to the outside world really consists of several servers
> that share the load, and that keep the hub up and running even if one
> of the servers stops working.
PSHB is mostly concerned with defining a virtual relationship
("topic") between publishers and subscribers. This includes basic
lifecycle and delivery properties. It tends to, where possible,
remain silent on certain "implementation details" so that they are
*not ruled out*. For example there are existing techniques for HTTP
server load management. PSHB could talk about such things but it
would then restrict behaviour to a subset of possible hubs, in a way
that is unnecessary for the main goal.
> Or, if the load to capture the
> publisher's source info backs up, is there some mechanism to share the
> load out?
Well, that's quite interesting. Yes you could imagine a 'routing
network' or 'federation' of hubs which could provide more than one way
to get a publication to a subscriber. But this would be an 'implicit'
behaviour; PSHB does not talk about "load" explicitly.
> I can see firms listing multiple hubs instead of one in thinking that
> this somehow provides for greater reliability, but I'm not sure that
> does anything but create multiple feeds that subscribers then have to
> true up. Thoughts?
Well, it's not unlike having multiple email servers.
alexis
