Connection to mongo db using dotnetcore

Question

I'm testing the beta of the new MongoDB.Driver for c# compatible with dotnet core and I can't get the connection to work. I have a mongo server v3.3 running on a docker container under port 27017 and I can sucessfully access through either the console via docker exec -it and a GUI (Robomongo).

I am using the "MongoDB.Driver": "2.3.0-beta1", in my project.json and the code I run is the following:

public class Program
{
    public static void Main(string[] args)
    {
        var client = new MongoClient("mongodb://localhost:27017");

        var db = client.GetDatabase("newdatabase");

        var collection = db.GetCollection<Person>("mycollection");

        collection.InsertOne(new Person{Id = "1", Age = 32});
    }

    public class Person
    {
        public string Id{ get; set;}
        public int Age{ get; set;}
    }
}

The exception I get back is:

A timeout occured after 30000ms selecting a server using CompositeServerSelector{ Selectors = WritableServerSelector, LatencyLimitingServerSelector{ AllowedLatencyRange = 00:00:00.0150000 } }. Client view of cluster state is { ClusterId : "1", ConnectionMode : "Automatic", Type : "Unknown", State : "Disconnected", Servers : [{ ServerId: "{ ClusterId : 1, EndPoint : "Unspecified/localhost:27017" }", EndPoint: "Unspecified/localhost:27017", State: "Disconnected", Type: "Unknown", HeartbeatException: "MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> System.PlatformNotSupportedException: This platform does not support connecting sockets to DNS endpoints via the instance Connect and ConnectAsync methods, due to the potential for a host name to map to multiple IP addresses and sockets becoming invalid for use after a failed connect attempt. Use the static ConnectAsync method, or provide to the instance methods the specific IPAddress desired.
   at System.Net.Sockets.Socket.Connect(IPAddress[] addresses, Int32 port)
   at System.Net.Sockets.Socket.Connect(String host, Int32 port)
   at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
   at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MongoDB.Driver.Core.Connections.TcpStreamFactory.<ConnectAsync>d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MongoDB.Driver.Core.Connections.TcpStreamFactory.<CreateStreamAsync>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MongoDB.Driver.Core.Connections.BinaryConnection.<OpenHelperAsync>d__48.MoveNext()
   --- End of inner exception stack trace ---
   at MongoDB.Driver.Core.Connections.BinaryConnection.<OpenHelperAsync>d__48.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MongoDB.Driver.Core.Servers.ServerMonitor.<HeartbeatAsync>d__27.MoveNext()" }] }.

Is there something obvious that I am missing or misconfiguring or is it early days for this driver to be used?

Answer 1

Actually if I change localhost to 127.0.0.1 it works. For some reason it doesn't like the name (note I'm using Docker Version 1.12.0-beta21 (build: 11019) 5a44e81a0513f32f5c49f7d2966570893451f32f if that's of any help).

Answer 2

Had the same problem running the dotnet core application in Kubernetes cluster hosted in Docker-Desktop on Windows. I've tried Debian and Alpine based images and had no luck. Also it doesn't seem to be a Docker issue, since any nslookup hostname from the pod resolves the correct IP address.

The only workaround I found is to resolve the hostnames to IP addresses before initializing the Mongo connection, so I end up with the utility method:

private string GetMongoConnectionStringWithIps(string connectionString) {
    var builder = new MongoUrlBuilder(connectionString);
    var servers = new List<MongoServerAddress>();
    foreach (var server in builder.Servers)
    {
        var address = Dns.GetHostAddresses(server.Host).FirstOrDefault(ip => ip.AddressFamily == AddressFamily.InterNetwork);
        servers.Add(new MongoServerAddress(address.ToString(), server.Port));
    }
    builder.Servers = servers;
    return builder.ToMongoUrl().ToString();
}