[BUG] intermittent leveldb iterator crash

[markspanbroek]

Observed this crash several times while running the unit tests on windows in the CI:

Assertion failed: dummy_versions_.next_ == &dummy_versions_

A quick search seems to indicate that this is likely caused by a leveldb iterator not being properly closed.

Example CI run:
https://github.com/codex-storage/nim-codex/actions/runs/11731259014/job/32682716194?pr=988#step:4:946

[benbierens]

I'm looking into this now.

[benbierens]

While running the test a million times:

[benbierens]

Also

How sure are we there's not an async issue going on here, there's unrelated to leveldb?
I've seen the leveldb error a few times (now I can't reproduce of course) but each time it showed up right after test availability size is reduced by request slot size when fully downloaded passes successfully.
Investigation continues...

[gmega]

Is this still happening @markspanbroek @benbierens?

[benbierens]

I haven't seen it since #995 got merged. But I also haven't been running the tests in giant loops.
Are you suspecting some instability somewhere?