C#•10mo ago

❔ MongoDb transactions in Asp.net core web api

Hello, i need some advice on what is the best thing to do. I am building asp.net core Web API with MongoDb identity. The logic goes like this controller > service > dbManagers. I want to implement transactions so i can revert db operation if anything goes wrong. Now i dont want to repeat myself and add using (var session = await _dbClient.StartSessionAsync()) in every method, instead i created a middleware:

public class DbTransactionMiddleware
{
  private readonly RequestDelegate _next;
  private readonly DbClient _dbClient;

  public DbTransactionMiddleware(RequestDelegate next, DbClient dbClient)
  {
    _next = next;
    _dbClient = dbClient;
  }

  public async Task InvokeAsync(HttpContext context)
  {
    using (var session = await _dbClient.StartSessionAsync())
    {
      session.StartTransaction();

      try
      {
        await _next(context);
        await session.CommitTransactionAsync();
      }
      catch (Exception ex)
      {
        await session.AbortTransactionAsync();
        throw;
      }
     }
    }
  }

public class DbTransactionMiddleware
{
  private readonly RequestDelegate _next;
  private readonly DbClient _dbClient;

  public DbTransactionMiddleware(RequestDelegate next, DbClient dbClient)
  {
    _next = next;
    _dbClient = dbClient;
  }

  public async Task InvokeAsync(HttpContext context)
  {
    using (var session = await _dbClient.StartSessionAsync())
    {
      session.StartTransaction();

      try
      {
        await _next(context);
        await session.CommitTransactionAsync();
      }
      catch (Exception ex)
      {
        await session.AbortTransactionAsync();
        throw;
      }
     }
    }
  }

But how can i access session object in my service. And what would be the better way to do something like this. Like what is best practice?

31 Replies

Unknown User•10mo ago

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Aljo_M•10mo ago

so i should put

    using (var session = await _dbClient.StartSessionAsync())

    using (var session = await _dbClient.StartSessionAsync())

in all my service methods?

Unknown User•10mo ago

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Aljo_M•10mo ago

okay sorry i misunderstood so, i should delete that middleware and register it as a scoped service, then inject it in lets say my UserService? let me just give you example:

public async Task<BaseResponse> RemoveUserAsync(string userId)
{
  var user = await _userManager.GetByIdAsync(userId);
  if (user == null)
    throw new UserNotFoundByIdException(userId);

  var removeFromCompanyResult = await
  _companyManager.RemoveUserFromAllCompaniesAsync(user.UserName);
  if (!removeFromCompanyResult.IsAcknowledged || removeFromCompanyResult.ModifiedCount > 1)
  throw new DatabaseErrorException($"Failed to remove user from companies that have it. User was not removed, run it again.", removeFromCompanyResult);
            
  var deleteUserResult = await _userManager.RemoveOneAsync(userId);
  if (!deleteUserResult.IsAcknowledged || deleteUserResult.DeletedCount != 1)
    throw new DatabaseErrorException($"Failed to remove user.", deleteUserResult);
            
  return BaseResponse.Succeeded("User deleted successfully");
}

public async Task<BaseResponse> RemoveUserAsync(string userId)
{
  var user = await _userManager.GetByIdAsync(userId);
  if (user == null)
    throw new UserNotFoundByIdException(userId);

  var removeFromCompanyResult = await
  _companyManager.RemoveUserFromAllCompaniesAsync(user.UserName);
  if (!removeFromCompanyResult.IsAcknowledged || removeFromCompanyResult.ModifiedCount > 1)
  throw new DatabaseErrorException($"Failed to remove user from companies that have it. User was not removed, run it again.", removeFromCompanyResult);
            
  var deleteUserResult = await _userManager.RemoveOneAsync(userId);
  if (!deleteUserResult.IsAcknowledged || deleteUserResult.DeletedCount != 1)
    throw new DatabaseErrorException($"Failed to remove user.", deleteUserResult);
            
  return BaseResponse.Succeeded("User deleted successfully");
}

this is in my UserService.cs how to implement it here?

Unknown User•10mo ago

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Aljo_M•10mo ago

i actually have dbClient and all dbManagers registered as singletons

Unknown User•10mo ago

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Aljo_M•10mo ago

i am a complete beginner, sorry but okay UserService is scoped

Unknown User•10mo ago

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Aljo_M•10mo ago

what would you do?

Unknown User•10mo ago

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Aljo_M•10mo ago

why is UserService scoped? okay, i can make it transient

Unknown User•10mo ago

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Aljo_M•10mo ago

i was asking what is better to do instead of that, in case that is not common practice?

Unknown User•10mo ago

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Aljo_M•10mo ago

i saw some example, and didnt want to use start transaction in all my methods

Unknown User•10mo ago

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Aljo_M•10mo ago

yes i understand that

Unknown User•10mo ago

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Aljo_M•10mo ago

yes ofcourse

Unknown User•10mo ago

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Aljo_M•10mo ago

yes okay

Unknown User•10mo ago

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Aljo_M•10mo ago

i get it

Unknown User•10mo ago

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Aljo_M•10mo ago

sure okay thanks

Unknown User•10mo ago

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Aljo_M•10mo ago

so i created a scoped service and kept the middleware. in the middleware i run the scoped service to create transaction and then set the session object into context like this:

context.Items["MongoSession"] = session;

context.Items["MongoSession"] = session;

this is just to play around. what do you think about it?

Unknown User•10mo ago

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Aljo_M•10mo ago

😂 okay thank you :)

Accord•10mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ MongoDb transactions in Asp.net core web api