CSHARP-671: server sometimes neglects to return setName causing the driver to think that the instance is not a replica set member and we remove it from memory preventing recovery.

Author: craiggwilson

MongoDB.Driver/CommandResults/IsMasterResult.cs

@@ -76,6 +76,17 @@ public bool IsPassive
             get { return Response.GetValue("passive", false).ToBoolean() && !IsArbiterOnly; }
         }
 
+        /// <summary>
+        /// Gets a value indicating whether this instance is replica set.
+        /// </summary>
+        /// <value>
+        ///   <c>true</c> if this instance is replica set; otherwise, <c>false</c>.
+        /// </value>
+        public bool IsReplicaSet
+        {
+            get { return ReplicaSetName != null || Response.GetValue("isreplicaset", false).ToBoolean(); }
+        }
+
         /// <summary>
         /// Gets whether the server is secondary.
         /// </summary>

MongoDB.Driver/Communication/MongoServerInstance.cs

@@ -562,7 +562,7 @@ private void LookupServerInformation(MongoConnection connection)
 
                 ReplicaSetInformation replicaSetInformation = null;
                 MongoServerInstanceType instanceType = MongoServerInstanceType.StandAlone;
-                if (isMasterResult.ReplicaSetName != null)
+                if (isMasterResult.IsReplicaSet)
                 {
                     var peers = isMasterResult.Hosts.Concat(isMasterResult.Passives).Concat(isMasterResult.Arbiters).ToList();
                     replicaSetInformation = new ReplicaSetInformation(isMasterResult.ReplicaSetName, isMasterResult.Primary, peers, isMasterResult.Tags);

MongoDB.Driver/Communication/Proxies/ReplicaSetMongoServerProxy.cs

@@ -179,7 +179,9 @@ protected override bool IsValidInstance(MongoServerInstance instance)
             // read _replicaSetName in a thread-safe way
             var replicaSetName = Interlocked.CompareExchange(ref _replicaSetName, null, null);
 
-            return replicaSetName == null || replicaSetName == instance.ReplicaSetInformation.Name;
+            return replicaSetName == null || 
+                instance.ReplicaSetInformation.Name == null || 
+                replicaSetName == instance.ReplicaSetInformation.Name;
         }
 
         /// <summary>

MongoDB.Driver/Communication/ReplicaSetInformation.cs

@@ -39,11 +39,6 @@ internal sealed class ReplicaSetInformation : IEquatable<ReplicaSetInformation>
         /// <param name="tagSet">The tag set.</param>
         public ReplicaSetInformation(string name, MongoServerAddress primary, IEnumerable<MongoServerAddress> members, ReplicaSetTagSet tagSet)
         {
-            if (name == null)
-            {
-                throw new ArgumentNullException("name");
-            }
-            
             _name = name;
             _primary = primary;
             _members = members == null ? new List<MongoServerAddress>() : members.ToList();