push synchronization request status indicator: status return from cn.synchronize
Push synchronization (cn.synchronize, mn.updateSystemMetadata) involves an end-user that might want to have an idea of how long until the queued action is going to take to complete. Something as simple as returning the place in line of the sync request might suffice as the indicator, or a more complete data packet, including the place in line and the queue velocity, could be attempted.
The real-world analogy for this kind of indictor is taking a number at the deli-counter: You don't know when you will be served, but you know how many people are in front of you.
This option involves at it's core, returning the status from the cn.synchronize call, instead of 'true'. In order to be informative to the end user, the mn.updateSystemMetadata which calls cn.synchronize would also need to return the status as well.