Major Description
TimePartitionedUpdateProcessor.lookupShardLeaderOfCollection looks up the Shard/Slice to talk to for the given collection. It currently picks the first active Shard/Slice but it has a TODO to route to the ideal one based on the router configuration of the target collection. There is similar code in CloudSolrClient & DistributedUpdateProcessor that should probably be refactored/standardized so that we don't have to repeat this logic.