Wsrtjtyk

We have a deadlock like behaviour in our production-environment and I wonder if we use semaphoreslim correctly.

In our restapi the code looks like this:

public async Task<IActionResult> CreateAsync([FromBody] SomeModel someModel)

{

    var result = await _someClass.CreateArende(someModel);



    return result;

}



public async Task<IActionResult> RegisterAsync([FromBody] SomeModel someModel)

{

    var result = await _someClass.RegisterArende(someModel);



    return result;

}

No semphoreslim in controller level of our API but in someClass looks like this:

public class SomeClass {



    protected static SemaphoreSlim _semphoreSlimCreateArende = new SemaphoreSlim(1, 1);



    public async virtual Task<SomeResponseDto> CreateArende(SomeModel someModel)

    {

        try

        {

            await _semphoreSlimCreateArende.WaitAsync();



        }

        finally

        {

            try

            {

                _semphoreSlimCreateArende.Release();

            }

            catch (Exception)

            {

            }

        }



        return new SomeResponseDto()

        {

            ...

        };

    }



    public async virtual Task<SomeResponseDto> RegisterArende(SomeModel someModel)

    {

        try

        {

            await _semphoreSlimCreateArende.WaitAsync();



        }

        finally

        {

            try

            {

                _semphoreSlimCreateArende.Release();

            }

            catch (Exception)

            {

            }

        }



        return new SomeResponseDto()

        {

            ...

        };

    }



}

Should the semaphoreslim be in the controller level instead? Or should i change the controllers actions to not be async?

This question is a little disjointed, however lets try to make sense of it a little

Firstly lets get the pattern right

try

{

    await _semphoreSlimCreateArende.WaitAsync();



    // do your sync work here



}

finally

{

    // if this throws you are certainly doing something wrong

    _semphoreSlimCreateArende.Release(); 

}

Secondly, you should have your keyboard taken away from you for this

catch (Exception)

{

}

Don't ever blindly eat exceptions, and if you are getting them on _semphoreSlimCreateArende.Release you have serious problems already and you have to work out why

Should the semaphoreslim be in the controller level instead?

Use them at the level that makes the most sense, i mean if you need to sync a piece of code sync it there, not 13 levels up.

Or should i change the controllers actions to not be async?

if you have asnyc work make your controller async and let it propagate down the stack to your async code

We have a deadlock like behaviour in our production-environment and i
wonder if we use semaphoreslim correctly.

Woah, are we talking DataBase Deadlocks, or Context DeadLocks. Either way this all sounds a little fishy

FYI

Using a SemaphoreSlim in a web based service can be a nasty approach. SemaphoreSlim works on a spin lock, and shouldn't be used for anything that blocks for any period of time. Spinlocks chew through the processor waiting for the lock to be released. Ideal you use them when there is a little of the lock biting, and in situations that don't block further down the chain.

If you are deadlocking code, then you need to work out exactly what is causing the deadlock, if its a task based deadlock, then SemaphoreSlim is not the right tool for the job, if it is a non blocking race condition then maybe its a little more acceptable. If its a Database deadlock, then you have bigger problem.