Concurrency

LiteDB v4 supports both thread-safe and process-safe:

• You can create a new instance of LiteRepository, LiteDatabase or LiteEngine in each use (process-safe)
• You can share a single LiteRepository, LiteDatabase or LiteEngine instance across your threads (thread-safe)

In first option (process safe), you will works always disconnected from datafile. Each use will open datafile, lock file (read or write mode), do your operation and then close datafile. Locks are implemented using FileStream.Lock for both read/write mode. It's very important in this way always use using statement to close datafile.

In second option (thread-safe) LiteDB control concurrency using ReaderWriterLockSlim .NET class. With this class it's possible manage multiple reads and an exclusive write. All threads share same instance and each method control concurrency.

Recommendation

Single instance is much faster than multi instances. In multi instances environment, each instance must do expensive data file operations: open, lock, unlock, read, close. Also, each instance has its own cache control and, if used only for a single operation, will discard all cached pages on close datafile. In single instance, all pages in cache are shared between all read threads.

If your application works in a single process (like mobile apps, asp.net websites) prefer use a single database instance and share across all threads.

You can use Exclusive mode (in connection string). Using exclusive mode datafile will avoid always checks header page to check if has any external change. Also, exclusive mode do not use Lock/Unlock in file, only in memory (using ReaderWriterLockSlim class).