public final class ShardCoreKeyMap
A map between segment core cache keys and the shard that these segments
belong to. This allows to get the shard that a segment belongs to or to get
the entire set of live core cache keys for a given index. In order to work
this class needs to be notified about new segments. It modifies the current
mappings as segments that were not known before are added and prevents the
structure from growing indefinitely by registering close listeners on these
segments so that at any time it only tracks live segments.
NOTE: This is heavy. Avoid using this class unless absolutely required.