Cap the blocking-pool thread count below LMDB's reader limit - #23683
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On large-core-count machines, `--rule-threads-max` (default 4x `--rule-threads-core`) can size the blocking thread pool well past LMDB's default 126-reader limit, causing `MDB_READERS_FULL` errors during local store reads. Clamp the pool to a safe ceiling, fix an underflow that could silently wrap the thread count instead of erroring, and warn when the configured thread counts get capped so the reduced parallelism isn't a silent surprise. Fixes pantsbuild#23652. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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On large-core-count machines,
--rule-threads-max(default 4x--rule-threads-core) can size the blocking thread pool well past LMDB's default 126-reader limit, causingMDB_READERS_FULLerrors during local store reads. Clamp the pool to a safe ceiling, fix an underflow that could silently wrap the thread count instead of erroring, and warn when the configured thread counts get capped so the reduced parallelism isn't a silent surprise.Fixes #23652.