[LUCENE-6437] Improve test reproducibility of ConcurrentMergeScheduler

• Type: Task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 5.2, 6.0
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Robert Muir
• Created: 17/Apr/15 23:58
• Updated: 28/Aug/22 14:31
• Resolved: 18/Apr/15 16:36

Description

If things go wrong based on merges with concurrentmergescheduler in tests, its always more difficult to reproduce.

But we make it worse, CMS can base its behavior on:

• number of cpus.
• whether drives are SSDs.

We should just allow a (undocumented, for testing) sysprop backdoor to override both of these. This way, it can be set to values completely based on the random seed in LuceneTestCase init, and its not a reproducibility trap.

Its true we try to set explicit values for LuceneTestCase.newIndexWriterConfig() and so forth. But not all tests use randomized IW configs.

Issue Links

• is related to: LUCENE-10576 ConcurrentMergeScheduler maxThreadCount calculation is artificially low