Push-based sync

“Guy English writes about iCloud”:http://kickingbear.com/blog/archives/202 and the magic glue (Push Notifications’ persistent connection) that makes it work:

“Each of these new features tickle the persistent ‘push’ connection and trigger some action on the device. The short-form state may be transmitted immediately and set on any connected device within moments. Document syncing is likely to trigger a negotiation process to compare the state on any one device with The Truth stored on Apple servers and replace the document on the device with the latest revision — this has the advantage of limiting the window between syncing where conflicts are most likely to occur.”

Sync speed matters. The first note sharing server I built for VitalSource years ago assumed a lot of offline time, and despite “my blogging in 2007 that it was”:http://www.manton.org/2007/01/bookshelf_note_sharing.html “magic”, in practice it could take 5-10 minutes before all your computers got their act together to get a set of highlights completely synced. With that kind of lag, note edits might happen on a client in the meantime, so we remembered conflicts everywhere and had a UI for resolving them.

Too complicated. The new system, recently rolled out in Bookshelf for iPhone and iPad, syncs so much more efficiently and quickly that conflicts don’t need the same emphasis. We can throw away a bunch of code and simplify the user interface.

I’ve yet to do anything with iCloud except read the release notes and sit through a couple WWDC sessions, but we’re going to have a fantastic platform if it can deliver the same speed and reliability of Push Notifications. Guy’s post is the first I’ve seen to connect the dots, capturing how well-positioned Apple is to use this plumbing for all sorts of stuff.