Arun Sirpal shows off a SQL Server 2017 and Azure SQL Database feature:
Clearly I am in a paused state with 5.48% percent of the operation complete. In the original query window where I started the index rebuild, I receive:
Msg 1219, Level 16, State 1, Line 4 Your session has been disconnected because of a high priority DDL operation. Msg 0, Level 20, State 0, Line 3
A severe error occurred on the current command. The results, if any, should be discarded.
DTUs when in a paused state, it drops back down to pretty much 0 DTU consumption (red arrow below).
If you have a hard nightly maintenance window to hit, being able to pause index rebuilds is a pretty nice feature.