Just started to look into Pubsubhubbub , and i am wondering if there is a guaranteed delivery mechanism in the protocol or it really depends on how the Hub implements it ?
thanks
Just started to look into Pubsubhubbub , and i am wondering if there is a guaranteed delivery mechanism in the protocol or it really depends on how the Hub implements it ?
thanks
I'm the founder of http://superfeedr.com and we host most PubSubHubbub hubs out here.
Well, I'm not sure what you mean by "guaranteed" delivery. If the publisher, the hub and the subscriber respect the protocol, then, yes, the delivery is guaranteed...
Now, we know that some publisher may not always ping us accurately. Some hubs may also have downtimes. To prevent that, we do a backup polling, which means that we'll poll each feed to make sure we haven't missed anything.
Similarly, it can happen that a subscriber is unable to process/handle the notifications, or at least the hub may not be able to reach them (despite retries). For these cases, we store the content of all past notifications and we allow subscribers to retrieve that conveniently.
Finally, we implemenent a "counter" approach that helps subscriber know that they haven't missed anything by sending incrementing a counter for each notification that we send them. If they see the counter decreased by more than 1, they know they've missed something.