Cassandra parallel data loader

There should be an option to warm up Ignite caches backed by Cassandra using loadCache method and distributing download process among all the nodes of Ignite cluster - downloading portion of data from Cassandra in parallel.

Each Ignite node responsible for a set of Ignite cache partitions. By providing some custom mapping structure to loadCache method it's rather easy to map Ignite partitions to "subpartitions" of Cassandra data slice which we are interested in. Such a way it will be possible to download all the data in parallel by utilizing all Ignite cluster nodes and running multiple download thread on each node.