[SOLR-8906] Make transient core cache pluggable.

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 6.6, 7.0
• Assignee: Erick Erickson
• Reporter: Erick Erickson
• Created: 25/Mar/16 19:38
• Updated: 10/Apr/19 18:48
• Resolved: 03/Apr/17 20:53

Description

The current Lazy Core stuff is pretty deeply intertwined in CoreContainer. Adding and removing active cores is based on a simple LRU mechanism, but keeping the right cores in the right internal structures involves a lot of attention to locking various objects to update internal structures. This makes it difficult/dangerous to use any other caching algorithms.

Any single age-out algorithm will have non-optimal access patterns, so making this pluggable would allow better algorithms to be substituted in those cases.

If we ever extend transient cores to SolrCloud, we need to have load/unload decisions that are cloud-aware rather then entirely local so in that sense this is would lay some groundwork if we ever want to go there.

So I'm going to try to hack together a PoC. Any ideas on the most sensible pattern for this gratefully received.

Issue Links

• is related to: LUCENE-8738 Bump minimum Java version requirement to 11
• is related to: SOLR-12560 remove deprecated NodeConfigBuilder.setTransientCacheSize