[RocksJava] Fix DefaultEnvTest.incBackgroundThreadsIfNeeded test

[sagar0]

DefaultEnvTest.incBackgroundThreadsIfNeeded jtest should assert that the number of threads is greater than or equal to the minimum number of threads.

Test Plan:
This test is failing on my system with an error like:

Expected: 20
Actual: 48

All tests now pass with this fix.

[riversand963]

Curious to know what caused the tests to fail.
Not familiar with Java part, but have a question. I checked https://github.com/facebook/rocksdb/blob/master/util/threadpool_imp.cc#L319 and https://github.com/facebook/rocksdb/blob/master/util/threadpool_imp.cc#L327, looks like we should expect the two to be equal?

[adamretter]

LGTM

[sagar0]

@riversand963 In my case defaultEnv.getBackgroundThreads(Priority.LOW) returns 48 even without calling incBackgroundThreadsIfNeeded(20). And since IncBackgroundThreadsIfNeeded(20) calls SetBackgroundThreadsInternal(20, /*allow_reduce*/ false), this fails for me ... as it is not supposed to reduce if it is already greater.

https://github.com/facebook/rocksdb/blob/master/util/threadpool_imp.cc#L319 happens only when allow_reduce=true for one of the conditions, on line 318. The other condition on line 317 doesn't apply here.

Hence the assert should be on isGreaterThanOrEqualTo(num) instead of just isEqualTo(num).

[facebook-github-bot]

@sagar0 has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.