Using cursor for iterating results I get "MongoDB.Driver.MongoCommandException: Command getMore failed: Cursor not found"

[Marcus Haßmann]

I get the following exception:

MongoDB.Driver.MongoCommandException: Command getMore failed: Cursor not found, cursor id: 16494659487.
   at MongoDB.Driver.Core.WireProtocol.CommandWireProtocol`1.ProcessReply(ConnectionId connectionId, ReplyMessage`1 reply)
   at MongoDB.Driver.Core.WireProtocol.CommandWireProtocol`1.Execute(IConnection connection, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.ClusterableServer.ServerChannel.ExecuteProtocol[TResult](IWireProtocol`1 protocol, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Servers.ClusterableServer.ServerChannel.Command[TResult](DatabaseNamespace databaseNamespace, BsonDocument command, IElementNameValidator commandValidator, Func`1 responseHandling, Boolean slaveOk, IBsonSerializer`1 resultSerializer, MessageEncoderSettings messageEncoderSettings, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.AsyncCursor`1.ExecuteGetMoreCommand(IChannelHandle channel, CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.AsyncCursor`1.GetNextBatch(CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.AsyncCursor`1.MoveNext(CancellationToken cancellationToken)
   at MongoDB.Driver.Core.Operations.AsyncCursorEnumerator`1.MoveNext()

I am using the newest NuGet packages:

  <package id="MongoDB.Bson" version="2.2.0" targetFramework="net452" />
  <package id="MongoDB.Driver" version="2.2.0" targetFramework="net452" />
  <package id="MongoDB.Driver.Core" version="2.2.0" targetFramework="net452" />

This is the executed code:

try
{
 var mylist = database.GetCollection<MyClass>("MyCollectionName");
 var cursor = mylist.Find(x => x.Subdocument.Any(y => y.BoolValue == false)).ToCursor();
 foreach (var myObject in cursor.ToEnumerable())
 {
 Console.WriteLine();
 Console.WriteLine("myObject-ID: " + myObject.myObjectId);


 var myObjectChanged = false;
 var subDocs = myObject.Subdocument.Where(x => x.BoolValue == false).ToList();
 var subDocCount = subDocs.Count;
 for (var i = 0; i < subDocCount; i++)
 {
 var myObject = subDocs[i];
 ...
 if (...)
 {
 myObjectChanged = true;
 }
 }


 if (myObjectChanged)
 {
 mylist.ReplaceOne(x => x.myObjectId == myObject.myObjectId, myObject);
 }
 }
}
catch (Exception ex)
{
 Console.WriteLine(ex);
}

[Robert Stam]

The most common reason for seeing a cursor not found error is that the server kills any cursors that have been idle for 10 minutes. The results of a query are returned from the server in batches. If it takes more than 10 minutes for an application to process a batch you will get this error when the driver attempts to get the next batch.

A less common reason for seeing a cursor not found error is when the mongos'es in a sharded cluster are deployed behind a load balancer. In this case the getMore command might be sent to a different mongos instance than the initial query. When this happens, the mongos instance receiving the getMore command can't find that cursor.

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[Marcus Haßmann]

Very nice answer, thank you very much!

With following changes, no MongoDB.Driver.MongoCommandException occured.

var findOptions = new FindOptions {NoCursorTimeout = true};
var count = myList.Find(filter).Count();
using (var cursor = myList.Find(filter, findOptions).ToCursor())
{
 while (cursor.MoveNext())
 {
 var index = 0;
 foreach (var myObject in cursor.Current)
 {

[Robert Stam]

Thanks for letting me know that adding NoCursorTimeout worked for you!

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