Indrivo.Utilities.ConcurrentConditionalAccessChecker 1.0.0

Indrivo.Utilities.ConcurrentConditionalAccessChecker

Name

CCAC (Conditional Concurrent Access Checker) code library

Description

This code library should be used in case if

1. There are multiple concurrent request to the same resource object from a single or multiple clients;
2. In order to eliminate duplicated idempotent requests;
3. Skip execution of a code block, if already exists a thread which executes the corresponding code block.

*The de veloper may use this code library in order to eliminate some POST requests, indicating the necessary condition (or other non idempotent ones, if it is necessary)...

This functionality is used in such projects as:

• DDWC.

Usage

1. Eliminate duplicated HTTP requests at the Controller's filters level. The events are considered duplicated if there is a matching condition between them:

//The filter applied abothe the endpoint:
[ConcurrencyAccessFilter(HttpMethod.Put, nameof(DossiersController), nameof(CompleteDossier))]
public async Task<IActionResult> CompleteDossier([FromBody] FinishCompleteDossierCommand command, CancellationToken cancellationToken)
{
    //...
}

//The implementation of the filter
//...
switch (endpoint)
{
    case "Put_DossiersController_CompleteDossier":
    {
        var request = JsonConvert.DeserializeObject<FinishCompleteDossierCommand>(requestContent);
        if (request != null)
        {
            var searchItem = new Wrapper<FinishCompleteDossierCommand>(request, DateTime.UtcNow.AddSeconds(15));
            bool SearchClause(FinishCompleteDossierCommand command) => command.DossierId == request.DossierId;

            var timeRemaining = await Utility.ConcurrentConditionalAccessChecker.VerifyThreadAsync(searchItem, SearchClause, LockRoom.FinishCompleteDossierLock);
            if (timeRemaining != null)
            {
                timeRemaining = timeRemaining < 5 ? 5 : timeRemaining;
                throw new ConditionalConcurrencyException(timeRemaining.Value, default);
            }
        }

        break;
    }
    //other endpoints here
    //...
}

2. Conditionally check if there is already a thread applied on the code block and skip it, if necessary:

// Let suppose that the action has been occurred on this dossier's Id in a previous action
var dossierId = Guid.NewGuid();

bool SearchClause(FinishCompleteDossierCommand item) => item.DossierId == dossierId;

if (await Utility.ConcurrentConditionalAccessChecker.VerifyThreadAsync(new Wrapper<FinishCompleteDossierCommand>(_command), SearchClause, LockRoom.FinishCompleteDossierLock, cancellationToken) == null)
{
    //Thread safe zone
    await Task.Run(() => Debug.WriteLine("Do Some action here"), cancellationToken);
}
//...

3. Do not forget to erase expired registrations from this utility (using cron jobs):

public class ConcurrencyJob : IAsyncJob
{
    public async Task ExecuteAsync()
    {
        await Utility.ConcurrentConditionalAccessChecker.DeleteExpiredAsync();
    }
}

*Use different objects from LockRoom, if you are dealing in code with distinct event types.

Tests

See examples from the ConcurrentConditionalAccessChecker.Tests code library.

Additional

For more examples see the ReferenceApplication, ConcurrentConditionalAccessChecker.CronJobs and ConcurrentConditionalAccessChecker.Usage code libraries from this repository.