Mongo transaction

[Osama-Amireh-1]

Hello Dear
I want to ask you if I can save audit after commit transaction in mongodb how I can handle this

[thepirat000]

Please provide more details. Are you auditing a MongoDB Entity Framework Core provider?

[Osama-Amireh-1]

No I am using mongo.driver
I want use audit log but when make transaction i don't need save log until commit transaction

[thepirat000]

Oh, I see what you mean now.

If your driver is connected to a MongoDB replica set, then each call to CommitTransaction() or AbortTransaction() should result in "commitTransaction" or "abortTransaction" audit events, respectively.

So if, within a single transaction, you insert one document and delete another, you should expect three audit events: "insert", "delete", and "commitTransaction" (or "abortTransaction" if it rolls back).

For example:

[
  {
    "Command": {
      "RequestId": 6,
      "OperationId": 2,
      "CommandName": "insert",
      "Body": {
        "insert": "TestColl",
        "ordered": true,
        "$db": "TestDb",
        "lsid": {
          "id": "e3418622-2296-4a93-9226-408bbcd5cda2"
        },
        "txnNumber": 2,
        "startTransaction": true,
        "autocommit": false,
        "documents": [
          {
            "_id": {
              "Timestamp": 1760144078,
              "CreationTime": "2025-10-11T00:54:38Z"
            },
            "x": 1
          }
        ]
      },
      "Duration": 7,
      "Success": true,
      "Timestamp": "2025-10-11T00:54:38.7334268Z"
    }
  },
  {
    "Command": {
      "RequestId": 7,
      "Connection": null,
      "OperationId": 3,
      "CommandName": "delete",
      "Body": {
        "delete": "TestColl",
        "ordered": true,
        "$db": "TestDb",
        "lsid": {
          "id": "e3418622-2296-4a93-9226-408bbcd5cda2"
        },
        "txnNumber": 2,
        "autocommit": false,
        "deletes": [
          {
            "q": {},
            "limit": 1
          }
        ]
      },
      "Duration": 4,
      "Success": true,
      "Timestamp": "2025-10-11T00:54:38.7653531Z"
    }
  },
  {
    "Command": {
      "RequestId": 8,
      "OperationId": 4,
      "CommandName": "commitTransaction",
      "Body": {
        "commitTransaction": 1,
        "$db": "admin",
        "lsid": {
          "id": "e3418622-2296-4a93-9226-408bbcd5cda2"
        },
        "txnNumber": 2,
        "autocommit": false
      },
      "Duration": 8,
      "Success": true,
      "Timestamp": "2025-10-11T00:54:38.7939639Z"
    }
  }
]

You’ll notice the three events share the same lsid and txnNumber, which confirms they are part of the same transaction.

To correlate all related events, use the logical session ID (lsid) together with the transaction number (txnNumber) from the command body.

https://www.mongodb.com/community/forums/t/how-to-find-queries-associated-with-a-transaction/117133

[Osama-Amireh-1]

this always insert not only when commint is it right?

how make this to insert also commit as event

because when create event it is save like this

/**

• Paste one or more documents here
  */
  {
  "EventType": "Update",
  "Environment": {
  "UserName": "o.amireh",
  "CallingMethodName": "Sky.NetCore.Repository.MongoRepositoryLogging`1.createAduitLog()",
  "Culture": "en-US"
  },
  "Target": {
  "Type": "Book",
  "New": {
  "Id": "68d26b915c7a517d95c70ab0",
  "BookId": 10,
  "Title": "osama",
  "ISBN": "osama",
  "Price": 10,
  "PublishedDate": "2025-09-23T09:58:23.332Z",
  "Authors": {
  "Name": "test",
  "Descreption": "test"
  },
  "DomainEvents": []
  }
  },
  "StartDate": "2025-09-23T09:58:58.1930154Z",
  "EndDate": "2025-09-23T09:58:58.9071196Z",
  "Duration": 714,
  "UserId": "TEST_USER_123",
  "UserName": "John Doe (Test User)",
  "UserEmail": "john.doe.test@company.com",
  "Application": "BookManagement"
  }

[thepirat000]

Now, if you need to save the intercepted commands after a transaction commit as a single event, you can implement your own Audit Data Provider by inheriting from AuditDataProvider (or any of the included providers).

You will need custom logic to maintain a list of events for ongoing transactions.

public class MyTransactionalDataProvider : AuditDataProvider
{
    private readonly ConcurrentDictionary<string, ConcurrentQueue<AuditEventMongoCommand>> _commands = new();

    public override object InsertEvent(AuditEvent auditEvent)
    {
        var mongoEvent = (AuditEventMongoCommand)auditEvent;
        var cmdName = mongoEvent.Command.CommandName;
        var body = (Dictionary<string, object>)mongoEvent.Command.Body;
        var isStartTransaction = (bool)(body.GetValueOrDefault("startTransaction", null) ?? false);
        var lsId = body.GetValueOrDefault("lsid", null) is Dictionary<string, object> dict ? dict.GetValueOrDefault("id") : string.Empty;
        var txnNumber = body.GetValueOrDefault("txnNumber", string.Empty).ToString();
        var tranId = $"{lsId}:{txnNumber}";

        if (isStartTransaction)
        {
            // New transaction started with this event, add it to the list of events for this transaction
            _commands[tranId] = new ConcurrentQueue<AuditEventMongoCommand>([mongoEvent]);            
            return null;
        }
        
        if ((cmdName == "commitTransaction" || cmdName == "abortTransaction") && _commands.TryRemove(tranId, out var eventList))
        {
            // Transaction ended, save all events as a single audit event
            Save(eventList.ToList(), cmdName);
            return null;
        }

        if (_commands.TryGetValue(tranId, out var list))
        {
            // Event belongs to an ongoing transaction, add it to the list
            list.Enqueue(mongoEvent);            
            return null;
        }

        // Not part of a transaction, save single event immediately
        Save(mongoEvent);
        return null;
    }

    public async override Task<object> InsertEventAsync(AuditEvent auditEvent, CancellationToken cancellationToken = default)
    {
        // Same as InsertEvent but asynchronous...
        throw new NotImplementedException();
    }

    private void Save(List<AuditEventMongoCommand> eventList, string cmdName)
    {
        // Save the commands in a transaction as a single audit event
        // cmdName indicates whether it was a commit or abort
        throw new NotImplementedException();
    }

    private void Save(AuditEventMongoCommand mongoEvent)
    {
        // Save a single command event that is not part of a transaction
        throw new NotImplementedException();
    }
}

This implementation is provided as a conceptual example and has not been thoroughly tested. You may need to adjust it to match your specific use case and ensure proper concurrency handling, error management, and persistence logic.

[Osama-Amireh-1]

But here we should also log an event when a transaction starts or commits to signify the end of the transaction, is that right?

If is it right I am working with unit of work so it responsible for transactions

[thepirat000]

There is no separate start transaction event. The first command in a transaction includes the startTransaction property set to true in its body, indicating that the transaction began before the command execution. You can modify the logic inside if (isStartTransaction) to record a start transaction event, and handle the transaction completion in the following if statement.