What happen if subscriber offline?

[Kegan Gan]

Hub push feeds to subscribers using a HTTP POST on a webhook callback
URL.

What if the subscriber were offline for a period of time? When the
subscriber is online again, can the subscriber get the all feeds that
were published since it went offline? (So that the subscriber does not
miss any feeds).

How does it work?

[Paul Kinlan]

Hi,

Whilst I have observed cross over of entries between notifications (that is the same entry delivered several times), you don't get an entire stream of atom entries you just get what was just published to the hub, so if your subscriber goes offline you will not get notification of entries in that intervening period.  I am new to pubsubhubbub so I could be wrong - but I don't see any mention in the spec, and I don't see much about recieving subscriptions notifications.

Paul

2009/8/26 Kegan Gan <ke...@kegan.info>

[Pádraic Brady]

The wiki has a few best practices outlined, one of which states:

"Hubs should retry publications of new content multiple itmes if the initial notification failed."

So Hubs should (not necessarily will) make a few attempts. If your Subscriber is offline for a long period, well there is no stored queue past whatever horizon Hubs may set for retries. Hubs are not required to hold messages until you come back online. If in doubt, you should have a fallback using normal polling after any downtime, whether it's a manual task or something run periodically to safeguard against a Hub going offline too...

Paddy

 

Pádraic Brady

http://blog.astrumfutura.com
http://www.survivethedeepend.com
OpenID Europe Foundation Irish Representative

---

From: Paul Kinlan <paul....@gmail.com>
To: pubsub...@googlegroups.com
Sent: Wednesday, August 26, 2009 8:05:29 PM
Subject: [pubsubhubbub] Re: What happen if subscriber offline?

[Brett Slatkin]

I agree with what Pádraic says here. I'd also point out that one of
the cool things that Superfeedr (and other proprietary hubs) can do is
actually spool notification delivery on your subscriber's behalf so
you don't actually lose any message. The reference/open hub will do
this for a short time period, but other federated hubs may choose to
store messages infinitely until they can be received by the
subscriber.

-Brett