pubsubhubbub - What is the difference between sync and async when sucribing to a feed?

Question

I am trying to implement pubsubhubbub as a subscriber to https://pubsubhubbub.appspot.com/

When it comes time to subscribe via the debuger the field verify type offers 2 possibilities:

• asynchronous
• synchronous

Unfortunately the section 5.2 subscription validation from PubSubHubbub Core 0.4 -- Working Draft doesn't give details about the verify type.

Does sync/async make any difference for the callback script when sucribing to a feed via pubsubhubbub ?

Answer 1

PubSubHubbub 0.4 brings many updates and enhancements.

Among them:

• Breaking change: “sync” mode of subscription verification has been removed.

Anf for information:

*hub.verify_token, permanent subscriptions and Hub-initiated subscription renewals have been also removed.*

from: https://groups.google.com/forum/#!msg/pubsubhubbub/7RPlYMds4RI/2mIHQTdV3aoJ

Answer: It makes no more difference now, just use async as verify type.