Add ability to disable backups;
Add autoreconnect option to sync output channel for data sockets. Still need to do the same for control sockets. No way to interrupt at the moment for scale-in/reconfig/shutdown. Also will probably want to have some way to interrupt when lowest cost downstream changes, but need to think about implications for timestamps downstream first.
Add ability to recreate a failed control socket for a sync channel.
Make new mechanism for reopening a control socket non-blocking; Extend send upstream/downstream to reopen control socket in the background if the connection fails. Should work for simple stateless queries with no runtime scale-in/out now, but the control logic for stateful operators and scale-in/out would probably need to change to handle send failures; Just noticed the control dispatcher actually takes a lock on the control socket, need to check whether this will interfere with the sync channel's internal control socket reconnect logic.
Add nonblocking send upstream/downstream methods to control dispatcher ; Add config option to make acks best effort.