The SparseCounterPoolController is a singleton, which works well for a single-core Solr installation, but not so well for multi-core. When multiple cores share the same pool controller, requests for the same field in different cores will lead to a constant invalidation of the allocated pools. The result of this is that the pool caches will be nearly useless.
There should be a separate SparseCounterPoolController for each core.
The SparseCounterPoolController is a singleton, which works well for a single-core Solr installation, but not so well for multi-core. When multiple cores share the same pool controller, requests for the same field in different cores will lead to a constant invalidation of the allocated pools. The result of this is that the pool caches will be nearly useless.
There should be a separate SparseCounterPoolController for each core.