[BUG] FindById throws SynchronizationLockException: The read lock is being released without being held.

[huyhu]

Version
5.0.5

Describe the bug
FindById sporadically throws System.Threading.SynchronizationLockException: "The read lock is being released without being held."

Code to Reproduce
Here how I use FindById -it is hard to reproduce the issue though

public T FindById<T>(int id)
{
    var data = database.GetCollection<T>(typeof(T).Name).FindById(new BsonValue(id));

    if (Equals(data, default(T)))
    {
        throw new InvalidOperationException($"Cannot find {typeof(T).Name} with id {id}");
    }
    return data;
}

Expected behavior
No exceptions.

Screenshots/Stacktrace
"ClassName": "System.Threading.SynchronizationLockException",
"Message": "The read lock is being released without being held.",
"Data": null,
"InnerException": null,
"HelpURL": null,
"StackTraceString": " at System.Threading.ReaderWriterLockSlim.ExitReadLock()\r\n at LiteDB.Engine.TransactionMonitor.ReleaseTransaction(TransactionService transaction)\r\n at LiteDB.Engine.QueryExecutor.ExecuteQuery(Boolean executionPlan)\r\n at LiteDB.Engine.LiteEngine.Query(String collection, Query query)\r\n at LiteDB.LiteQueryable1.<ToDocuments>d__26.MoveNext()\r\n at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()\r\n at

Additional context
Add any other context about the problem here.

[huyhu]

@mbdavid I have the fix for this issue, but I cannot publish my branch to remote. Could you give me the permissions to do so?

[lbnascimento]

@huyhu Can't you make a pull request?

[huyhu]

@huyhu Can't you make a pull request?

remote: Permission to mbdavid/LiteDB.git denied to huyhu.
fatal: unable to access 'https://github.com/mbdavid/LiteDB.git/': The requested URL returned error: 403

[lbnascimento]

@huyhu You should create a fork of LiteDB, make your changes there and then submit a pull request.

[huyhu]

@huyhu You should create a fork of LiteDB, make your changes there and then submit a pull request.

@lbnascimento Could you please review the pull request?

[mefateah]

Looks like I had the same issue with FindAll method

[tualatin]

Looks like I had the same issue with FindAll method

Here the same, FindAll throws a SynchronizationLockException, but only, when I start my app without Visual Studio and I attach the debugger to my app. When I start my app with Visual Studio, all works fine.

[tdmboro]

Any progress on this or 2017, which I think are related? I'm getting the same SynchronizationLogException when iterating through a GetAll<T> collection. It's not intermittent for me but happens at the same document each time.

[aaubry]

I am also experiencing this error, and after investigating it seems that the problem is when using async code. I noticed that sometimes my transaction starts on a thread and completes in a different thread because I called some async method in between. Because ReaderWriterLock has thread affinity, the lock isn't being held from that thread's perspective.

I don't really know how to fix this. I suppose that using a synchronization object that has no thread affinity would work.

Meanwhile there are two workarounds I can think of.
The first one is to avoid mising async code with this library, which may be problematic depending on the application.
The other is to use a synchronization context that always executes on the same thread. I've used the SingleThreadSynchronizationContext implementation. The downside is that any paralelism is prevented while using it.

[Pete-PlaytimeSolutions]

I am also experiencing this error, but only when running tests under the net48 framework,
net60 framework tests completed without error.

Has the fix @huyhu suggested for this been verified/implemented yet?
I'm using the latest LiteDB version 5.0.15

[Pete-PlaytimeSolutions]

Just an update,
The suggested fix by @huyhu solved my issues, but have had to fork the code base, hopefully temporarily :)