Major Description
Perhaps the final piece of SOLR-6491. Once the preferred leadership roles are assigned, there has to be a command "make it so Mr. Solr". This is something of a placeholder to collect ideas. One wouldn't want to flood the system with hundreds of re-assignments at once. Should this be synchronous or asnych? Should it make the best attempt but not worry about perfection? Should it???
a collection=name parameter would be required and it would re-elect all the leaders that were on the 'wrong' node
I'm thinking an optionally allowing one to specify a shard in the case where you wanted to make a very specific change. Note that there's no need to specify a particular replica, since there should be only a single preferredLeader per slice.
This command would do nothing to any slice that did not have a replica with a preferredLeader role. Likewise it would do nothing if the slice in question already had the leader role assigned to the node with the preferredLeader role.