Rob Eamon wrote: > > > --- In [email protected] > <mailto:service-orientated-architecture%40yahoogroups.com>, "Steve Jones" > <[EMAIL PROTECTED]> wrote: > > > > Guessing at not powerful, RSS/Atom is a pull model, you often want > > Push as well in pub/sub. > > Good point. When searching for tools, keep this in mind as there are > pub/sub products out there that are pull-only, so if push is essential > you'll want to make sure the product really does that. For example, the > webMethods Broker never pushes--all adapters and clients always pull. > > On the other hand, pulling frequently enough is often sufficient.
With many pub/sub usages, the act of connecting, subscribing and then waiting for a publish, is similar to pull. When it is different, and scales better, is when the subscription actually provides for async delivery. The main issue with async delivery, is that it has limitations similar to "call backs" in that both network paths producer->consumer and consumer->producer must be routable in the context of the utilized connection technologies. On the internet, in general, TCP is not fully routable for all producer->consumer paths to make connections. Gregg Wonderly
