CSHARP-2571: Prefer connectionId from isMaster response to connectionid from getLastError response

Author: MikalaiMazurenka

src/MongoDB.Driver.Core/Core/Connections/ConnectionInitializer.cs

@@ -53,16 +53,24 @@ public ConnectionDescription InitializeConnection(IConnection connection, Cancel
 
             AuthenticationHelper.Authenticate(connection, description, cancellationToken);
 
-            try
+            var connectionIdServerValue = isMasterResult.ConnectionIdServerValue;
+            if (connectionIdServerValue.HasValue)
             {
-                var getLastErrorProtocol = CreateGetLastErrorProtocol();
-                var getLastErrorResult = getLastErrorProtocol.Execute(connection, cancellationToken);
-
-                description = UpdateConnectionIdWithServerValue(description, getLastErrorResult);
+                description = UpdateConnectionIdWithServerValue(description, connectionIdServerValue.Value);
             }
-            catch
+            else
             {
-                // if we couldn't get the server's connection id, so be it.
+                try
+                {
+                    var getLastErrorProtocol = CreateGetLastErrorProtocol();
+                    var getLastErrorResult = getLastErrorProtocol.Execute(connection, cancellationToken);
+
+                    description = UpdateConnectionIdWithServerValue(description, getLastErrorResult);
+                }
+                catch
+                {
+                    // if we couldn't get the server's connection id, so be it.
+                }
             }
 
             return description;
@@ -82,16 +90,26 @@ public async Task<ConnectionDescription> InitializeConnectionAsync(IConnection c
 
             await AuthenticationHelper.AuthenticateAsync(connection, description, cancellationToken).ConfigureAwait(false);
 
-            try
+            var connectionIdServerValue = isMasterResult.ConnectionIdServerValue;
+            if (connectionIdServerValue.HasValue)
             {
-                var getLastErrorProtocol = CreateGetLastErrorProtocol();
-                var getLastErrorResult = await getLastErrorProtocol.ExecuteAsync(connection, cancellationToken).ConfigureAwait(false);
-
-                description = UpdateConnectionIdWithServerValue(description, getLastErrorResult);
+                description = UpdateConnectionIdWithServerValue(description, connectionIdServerValue.Value);
             }
-            catch
+            else
             {
-                // if we couldn't get the server's connection id, so be it.
+                try
+                {
+                    var getLastErrorProtocol = CreateGetLastErrorProtocol();
+                    var getLastErrorResult = await getLastErrorProtocol
+                        .ExecuteAsync(connection, cancellationToken)
+                        .ConfigureAwait(false);
+
+                    description = UpdateConnectionIdWithServerValue(description, getLastErrorResult);
+                }
+                catch
+                {
+                    // if we couldn't get the server's connection id, so be it.
+                }
             }
 
             return description;
@@ -132,14 +150,20 @@ private BsonDocument CreateInitialIsMasterCommand(IReadOnlyList<IAuthenticator>
 
         private ConnectionDescription UpdateConnectionIdWithServerValue(ConnectionDescription description, BsonDocument getLastErrorResult)
         {
-            BsonValue connectionIdBsonValue;
-            if (getLastErrorResult.TryGetValue("connectionId", out connectionIdBsonValue))
+            if (getLastErrorResult.TryGetValue("connectionId", out var connectionIdBsonValue))
             {
-                var connectionId = description.ConnectionId.WithServerValue(connectionIdBsonValue.ToInt32());
-                description = description.WithConnectionId(connectionId);
+                description = UpdateConnectionIdWithServerValue(description, connectionIdBsonValue.ToInt32());
             }
 
             return description;
         }
+
+        private ConnectionDescription UpdateConnectionIdWithServerValue(ConnectionDescription description, int serverValue)
+        {
+            var connectionId = description.ConnectionId.WithServerValue(serverValue);
+            description = description.WithConnectionId(connectionId);
+
+            return description;
+        }
     }
 }

src/MongoDB.Driver.Core/Core/Connections/IsMasterResult.cs

@@ -69,6 +69,22 @@ public IReadOnlyList<CompressorType> Compressions
             }
         }
 
+        /// <summary>
+        /// Gets the connection id server value.
+        /// </summary>
+        public int? ConnectionIdServerValue
+        {
+            get
+            {
+                if (_wrapped.TryGetValue("connectionId", out var connectionIdBsonValue))
+                {
+                    return connectionIdBsonValue.ToInt32();
+                }
+
+                return null;
+            }
+        }
+
         /// <summary>
         /// Gets the election identifier.
         /// </summary>

tests/MongoDB.Driver.Core.Tests/Core/Connections/ConnectionInitializerTests.cs

@@ -39,6 +39,34 @@ public ConnectionInitializerTests()
             _subject = new ConnectionInitializer("test", new [] { new CompressorConfiguration(CompressorType.Zlib) });
         }
 
+        [Theory]
+        [ParameterAttributeData]
+        public void InitializeConnection_should_acquire_connectionId_from_isMaster_response([Values(false, true)] bool async)
+        {
+            var isMasterReply = MessageHelper.BuildReply(
+                RawBsonDocumentHelper.FromJson("{ ok : 1, connectionId : 1 }"));
+            var buildInfoReply = MessageHelper.BuildReply(
+                RawBsonDocumentHelper.FromJson("{ ok : 1, version : \"4.2.0\" }"));
+
+            var connection = new MockConnection(__serverId);
+            connection.EnqueueReplyMessage(isMasterReply);
+            connection.EnqueueReplyMessage(buildInfoReply);
+
+            ConnectionDescription result;
+            if (async)
+            {
+                result = _subject.InitializeConnectionAsync(connection, CancellationToken.None).GetAwaiter().GetResult();
+            }
+            else
+            {
+                result = _subject.InitializeConnection(connection, CancellationToken.None);
+            }
+
+            var sentMessages = connection.GetSentMessages();
+            sentMessages.Should().HaveCount(2);
+            result.ConnectionId.ServerValue.Should().Be(1);
+        }
+
         [Theory]
         [ParameterAttributeData]
         public void InitializeConnection_should_throw_an_ArgumentNullException_if_the_connection_is_null(