Hi community,
We’re facing intermittent connection issues with our MongoDB Atlas replica set from our application running on AKS (Azure Kubernetes Service, C# application). The connection fails with the following error:
A timeout occurred after 5000ms selecting a server using CompositeServerSelector{ Selectors = ReadPreferenceServerSelector{ ReadPreference = { Mode : Secondary } }, LatencyLimitingServerSelector{ AllowedLatencyRange = 00:00:00.0150000 }, OperationsCountServerSelector }. Client view of cluster state is { ClusterId : “2”, ConnectionMode : “ReplicaSet”, Type : “ReplicaSet”, State : “Disconnected”, Servers : [{ ServerId: “{ ClusterId : 2, EndPoint : “Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1024” }”, EndPoint: “Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1024”, ReasonChanged: “Heartbeat”, State: “Disconnected”, ServerVersion: , TopologyVersion: , Type: “Unknown”, HeartbeatException: “MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. —> System.Net.Sockets.SocketException (00000001, 11): Resource temporarily unavailable at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily, Nullable1 startingTimestamp) at System.Net.Dns.GetHostAddresses(String hostNameOrAddress, AddressFamily family) at MongoDB.Driver.Core.Connections.TcpStreamFactory.ResolveEndPoints(EndPoint initial) at MongoDB.Driver.Core.Connections.TcpStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.SslStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) --- End of inner exception stack trace --- at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.Open(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.InitializeConnection(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.Heartbeat(CancellationToken cancellationToken)", LastHeartbeatTimestamp: "2025-07-23T21:09:34.9034342Z", LastUpdateTimestamp: "2025-07-23T21:09:34.9034342Z" }, { ServerId: "{ ClusterId : 2, EndPoint : "Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1025" }", EndPoint: "Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1025", ReasonChanged: "Heartbeat", State: "Disconnected", ServerVersion: , TopologyVersion: , Type: "Unknown", HeartbeatException: "MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> System.Net.Sockets.SocketException (00000001, 11): Resource temporarily unavailable at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily, Nullable1 startingTimestamp) at System.Net.Dns.GetHostAddresses(String hostNameOrAddress, AddressFamily family) at MongoDB.Driver.Core.Connections.TcpStreamFactory.ResolveEndPoints(EndPoint initial) at MongoDB.Driver.Core.Connections.TcpStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.SslStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) — End of inner exception stack trace — at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.Open(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.InitializeConnection(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.Heartbeat(CancellationToken cancellationToken)”, LastHeartbeatTimestamp: “2025-07-23T21:09:34.9014263Z”, LastUpdateTimestamp: “2025-07-23T21:09:34.9014264Z” }, { ServerId: “{ ClusterId : 2, EndPoint : “Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1026” }”, EndPoint: “Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1026”, ReasonChanged: “Heartbeat”, State: “Disconnected”, ServerVersion: , TopologyVersion: , Type: “Unknown”, HeartbeatException: “MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. —> System.Net.Sockets.SocketException (00000001, 11): Resource temporarily unavailable at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily, Nullable1 startingTimestamp) at System.Net.Dns.GetHostAddresses(String hostNameOrAddress, AddressFamily family) at MongoDB.Driver.Core.Connections.TcpStreamFactory.ResolveEndPoints(EndPoint initial) at MongoDB.Driver.Core.Connections.TcpStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.SslStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) --- End of inner exception stack trace --- at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.Open(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.InitializeConnection(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.Heartbeat(CancellationToken cancellationToken)", LastHeartbeatTimestamp: "2025-07-23T21:09:30.8992301Z", LastUpdateTimestamp: "2025-07-23T21:09:30.8992302Z" }, { ServerId: "{ ClusterId : 2, EndPoint : "Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1031" }", EndPoint: "Unspecified/pl-0-westeurope-azure.vq7ef.mongodb.net:1031", ReasonChanged: "Heartbeat", State: "Disconnected", ServerVersion: , TopologyVersion: , Type: "Unknown", HeartbeatException: "MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> System.Net.Sockets.SocketException (00000001, 11): Resource temporarily unavailable at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily, Nullable1 startingTimestamp) at System.Net.Dns.GetHostAddresses(String hostNameOrAddress, AddressFamily family) at MongoDB.Driver.Core.Connections.TcpStreamFactory.ResolveEndPoints(EndPoint initial) at MongoDB.Driver.Core.Connections.TcpStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.SslStreamFactory.CreateStream(EndPoint endPoint, CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) — End of inner exception stack trace — at MongoDB.Driver.Core.Connections.BinaryConnection.OpenHelper(CancellationToken cancellationToken) at MongoDB.Driver.Core.Connections.BinaryConnection.Open(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.InitializeConnection(CancellationToken cancellationToken) at MongoDB.Driver.Core.Servers.ServerMonitor.Heartbeat(CancellationToken cancellationToken)”, LastHeartbeatTimestamp: “2025-07-23T21:09:31.3994102Z”, LastUpdateTimestamp: “2025-07-23T21:09:31.3994103Z” }] }.
Any help or guidance from the Atlas team or community would be greatly appreciated!