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Type:
Bug
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Resolution: Fixed
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Priority:
Unknown
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Affects Version/s: 2.14.0
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Component/s: None
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None
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Minor Change
Assume a program contains an error in CommandSucceededEvent event handler:
using System; using MongoDB.Driver; using MongoDB.Driver.Core.Events; namespace MongoDbStackBug { class Program { static void Main(string[] args) { var mongoClientSettings = MongoClientSettings.FromConnectionString("mongodb://localhost:27017/test"); mongoClientSettings.ClusterConfigurator = cc => { cc.Subscribe<CommandSucceededEvent>(cmd => { Console.WriteLine($"Command duration {cmd.Duration}"); // NRE here ((object)null).ToString(); }); }; var mongoClient = new MongoClient(mongoClientSettings); mongoClient.GetDatabase("test").ListCollections(); } } }
Actual behavior
The program throws an exception and the exception stack looks like MongoDB driver internal error
Duration 00:00:00.0091552 Unhandled exception. MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> System.NullReferenceException: Object reference not set to an instance of an object. at MongoDB.Driver.Core.Connections.BinaryConnection.ReceiveMessage(Int32 responseTo, IMessageEncoderSelector encoderSelector, MessageEncoderSettings messageEncoderSettings, CancellationToken cancellationToken) at MongoDB.Driver.Core.WireProtocol.CommandUsingQueryMessageWireProtocol`1.Execute(IConnection connection, CancellationToken cancellationToken) at MongoDB.Driver.Core.WireProtocol.CommandWireProtocol`1.Execute(IConnection connection, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.HelloHelper.GetResult(IConnection connection, CommandWireProtocol`1 helloProtocol, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.ConnectionInitializer.SendHello(IConnection connection, CancellationToken cancellationToken)
(I clipped the rest of the stack)
Expected behavior
On top of the stack trace should have been a frame with my faulty code. Without that, it is hard to find if there is an error in my code.
My suggestion
I believe the stack trace is cut because of `throw ex` in this code https://github.com/mongodb/mongo-csharp-driver/blob/1123d60823c8c3fc42246282cddfecc8b76479e6/src/MongoDB.Driver.Core/Core/Connections/BinaryConnection.cs#L522 (and some other places) If an exception is not wrapped, then it should be just 'throw', without ex.