[Neo Core] Ensure LevelDB Snapshot Only be Used by One Thread

[Jim8y]

Description

Leveldb is not thread safe, thus we should be able to avoid leveldb being used cross threads.

Fixes # (issue)

Type of change

• Optimization (the change is only an optimization)
• Style (the change is only a code style for better maintenance or standard purpose)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• TestOneThreadLevelDbSnapshotPut
• TestSingleExtraThreadLevelDbSnapshotPut
• TestMultiThreadLevelDbSnapshotPut

Test Configuration:

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[cschuchardt88]

Why are you trying to do this?

[Jim8y]

Why are you trying to do this?

trying to avoid leveldb mis use. Like in the previous unhandled plugin exception pr, snapshot was careless and unintentionally used in multiple threads, but there was no warning or exception at all. Thus having this pr, if it can not being used cross thread, then it should throw exception if its being used that way.

[shargon]

This was tested in a real environment?

[cschuchardt88]

This was tested in a real environment?

This should be tested in real environment. Reason is the blockchain network (node) is multi-threaded. Each request runs on a different thread, because of Akka.net.

[vncoelho]

Hi @Jim8y , maybe move to draft or this still should be reviewed?

[cschuchardt88]

This is way to much work needed. Plus it isn't correctly. #3414 fixes the problem.