CSHARP-791: Don't let an exception on one connection cause us to think that we are no longer connected to the server.

Author: rstam

MongoDB.Driver/Communication/MongoConnection.cs

@@ -356,9 +356,7 @@ private void HandleException(Exception ex)
                     throw new MongoInternalException("Invalid HandleExceptionAction");
             }
 
-            // forces a call to VerifyState before the next message is sent to this server instance
-            // this is a bit drastic but at least it's safe (and perhaps we can optimize a bit in the future)
-            _serverInstance.SetState(MongoServerState.Unknown);
+            _serverInstance.RefreshStateAsSoonAsPossible();
         }
 
         private enum HandleExceptionAction

MongoDB.Driver/Communication/MongoServerInstance.cs

@@ -349,6 +349,14 @@ public void Ping()
             }
         }
 
+        /// <summary>
+        /// Refreshes the state as soon as possible.
+        /// </summary>
+        public void RefreshStateAsSoonAsPossible()
+        {
+            _stateVerificationTimer.Change(TimeSpan.Zero, TimeSpan.FromSeconds(10)); // verify state as soon as possible
+        }
+
         /// <summary>
         /// Verifies the state of the server instance.
         /// </summary>

MongoDB.Driver/MongoServerState.cs

@@ -37,10 +37,6 @@ public enum MongoServerState
         /// </summary>
         ConnectedToSubset,
         /// <summary>
-        /// The state is temporarily unknown.
-        /// </summary>
-        Unknown,
-        /// <summary>
         /// Disconnecting from the server (in progress).
         /// </summary>
         Disconnecting

MongoDB.Driver/Operations/QueryOperation.cs

@@ -115,6 +115,15 @@ public IEnumerator<TDocument> Execute(IConnectionProvider connectionProvider)
                     }
                 }
             }
+            catch
+            {
+                if (reply != null && reply.CursorId != 0)
+                {
+                    try { KillCursor(connectionProvider, reply.CursorId); }
+                    catch { } // ignore exceptions and rethrow the original exception
+                }
+                throw;
+            }
             finally
             {
                 if (reply != null && reply.CursorId != 0)