[GitHub] [lucene] rmuir commented on pull request #12013: Clear thread local values on UTF8TaxonomyWriterCache.close()

[GitBox <gi...@apache.org>]

rmuir commented on PR #12013:
URL: https://github.com/apache/lucene/pull/12013#issuecomment-1347422875

   Thanks, it looks better to use `CloseableThreadLocal` than `ThreadLocal`... but I don't understand what this "cache" is doing and why it actually documents that it never frees memory. Especially as a default!
   
   As a followup can we open an issue to move away from Threadlocal storage here by default? I don't understand why we have this "cache" with this description:
   ```
   /** A "cache" that never frees memory, and stores labels in a BytesRefHash (utf-8 encoding). */
   ```
   
   Also, I'm trying to remove ThreadLocal (and CloseableThreadLocal) usages elsewhere in the codebase (e.g. #11998). These threadlocals are problematic in java apps that have many threads (or high thread churn rate), just as CloseableThreadLocal documents and attempts to workaround.
   
   At a glance, seems to me that using a bounded LRU cache would be much more reasonable...


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