FTS - Configurable Index Level FeedAllotmentOption

In the context of improving the resource usage with index handling, I was just checking the possibility of making the DCP to "Partition/Index" mapping (FeedAllotmentOption) as a part of the index definition, rather than as a manager Options as of now.

This would help in better tuning of the resource with indexes.

Let’s say, 

1) Index with huge set of documents with high mutation volume -> 1:1 mapping between DCP connection and pindex/partition would be recommended.

We can keep this as the default as well. That would also help the user to achieve high initial indexing throughput and later the user can update the mapping to according to the load.

2) Smaller/Large buckets with low to medium mutations -> 1:n, meaning all the partitions residing in a node will be fed by a single DCP connection.

By making this “FeedAllotmentOption” as a part of the index definition, the user can update the definition at any point in time to reflect the load/requirements of the index and adjust the resource utilisation. This also helps in higher capacity handling.

And such index definition update need not involve the recreation of the index, we can just restart the pindexes and hook up the new feed for the whole partitions of the index in that node.