We're using Seq as a central log server for our microservices. Services are written in C# using NLog for structured logging.

NuGet packages (all in current version)

• NLog
• NLog.Extensions.Logging
• NLog.Targets.Seq

For a few months we're seeing this error in the logs of all our applications that talk to our seq instance:

System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host..
 ---> System.Net.Sockets.SocketException (10054): An existing connection was forcibly closed by the remote host.
   at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.CreateException(SocketError error, Boolean forAsyncThrow)
   at System.Net.Sockets.NetworkStream.ReadAsync(Memory`1 buffer, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnection.PrepareForReuse(Boolean async)
   at System.Net.Http.HttpConnectionPool.TryGetPooledHttp11Connection(HttpRequestMessage request, Boolean async, HttpConnection& connection, HttpConnectionWaiter`1& waiter)
   at System.Net.Http.HttpConnectionPool.SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
   at System.Net.Http.HttpConnectionPool.SendAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPoolManager.SendAsyncCore(HttpRequestMessage request, Uri proxyUri, Boolean async, Boolean doRequestAuth, Boolean isProxyConnect, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPoolManager.SendAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpMessageHandlerStage.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.SocketsHttpHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.<SendAsync>g__Core|83_0(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken)
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
   at NLog.Targets.Seq.SeqTarget.SendPayload(StringBuilder payload)
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
   at NLog.Targets.Seq.SeqTarget.PostBatch(IList`1 logEvents)
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[TStateMachine](TStateMachine& stateMachine)
   at NLog.Targets.Seq.SeqTarget.PostBatch(IList`1 logEvents)
   at NLog.Targets.Seq.SeqTarget.Write(IList`1 logEvents)
   at NLog.Targets.Target.WriteAsyncThreadSafe(IList`1 logEvents)
   at NLog.Targets.Target.WriteAsyncLogEvents(IList`1 logEvents)
   at NLog.Targets.Wrappers.AsyncTargetWrapper.WriteLogEventsInQueue(Int32 batchSize, String reason)
   at NLog.Targets.Wrappers.AsyncTargetWrapper.ProcessPendingEvents(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.TimerQueueTimer.Fire(Boolean isThreadPool)
   at System.Threading.TimerQueue.FireNextTimers()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
--- End of stack trace from previous location ---

   --- End of inner exception stack trace ---

The error occurs randomly but consistently multiple times throughout the day. We've been investigating this issue for a while, but finding nothing. Hope someone may have encountered this or a similar issue. Any input appreciated!