s-j-upload currently supports a single remote target for streaming logs to. Ticket https://bugs.freedesktop.org/show_bug.cgi?id=89184 is an RFE to expand this to provide more than 1 target for failover purposes.
This ticket is requesting that the targets can be used in a load-balanced manner.
At this point, I don't believe the method of load balancing is important. If a pair (or more) of log receivers are built to cater for failover, it would not be wise for all logs to go to the receiver #1 under normal circumstances, only to use receiver #2 in failover circumstances. Clients could be configured to randomly swap the order of --url targets at configuration time, but this still allows the heaviest systems to end up with the same receiver #1.
I'm not sure if it would be insensible to round-robin every log entry across the configured targets, or whether a randomised timer could call for a switch-over at reasonable points.