Multithreaded compaction

[jankotek]

Multithreaded code should:

• Find Key without lock, just semaphore to prevent file from being delete
  • JVM crash if MappedByteBuffer is released during file traversal
• separate background task to delete unused and invalidated files
  • files are unmodifiable, unless invalidated and their semaphore is released
• per-file locking for Updates
• Structural Lock for creating new files, branching, cleanup and rollback
• Store Open code traverses all files, parallelize per file