downgrade inner httpconnection error to warning (#482)

* downgrade inner httpconnection error to warning, improve exception message

* Add comments

src/Microsoft.Azure.SignalR.Common/ServiceConnections/ConnectionFactory.cs

@@ -10,6 +10,7 @@
 using Microsoft.AspNetCore.Http.Connections;
 using Microsoft.AspNetCore.Http.Connections.Client;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
 
 namespace Microsoft.Azure.SignalR
 {
@@ -27,7 +28,7 @@ internal class ConnectionFactory : IConnectionFactory
         public ConnectionFactory(string hubName, IServiceEndpointProvider provider, IServerNameProvider nameProvider, ILoggerFactory loggerFactory)
         {
             _provider = provider ?? throw new ArgumentNullException(nameof(provider));
-            _loggerFactory = loggerFactory;
+            _loggerFactory = loggerFactory == null ? (ILoggerFactory)NullLoggerFactory.Instance : new GracefulLoggerFactory(loggerFactory);
             _userId = nameProvider?.GetName();
             _hubName = hubName;
         }
@@ -83,5 +84,68 @@ public Task DisposeAsync(ConnectionContext connection)
 
             return ((HttpConnection)connection).DisposeAsync();
         }
+
+        private sealed class GracefulLoggerFactory : ILoggerFactory
+        {
+            private readonly ILoggerFactory _inner;
+            public GracefulLoggerFactory(ILoggerFactory inner)
+            {
+                _inner = inner;
+            }
+
+            public void Dispose()
+            {
+                _inner.Dispose();
+            }
+
+            public ILogger CreateLogger(string categoryName)
+            {
+                var innerLogger = _inner.CreateLogger(categoryName);
+                return new GracefulLogger(innerLogger);
+            }
+
+            public void AddProvider(ILoggerProvider provider)
+            {
+                _inner.AddProvider(provider);
+            }
+
+            private sealed class GracefulLogger : ILogger
+            {
+                private readonly ILogger _inner;
+                public GracefulLogger(ILogger inner)
+                {
+                    _inner = inner;
+                }
+
+                /// <summary>
+                /// Downgrade error level logs, and also exclude exception details
+                /// Exceptions thrown from inside the HttpConnection are supposed to be handled by the caller and logged with more user-friendly message
+                /// </summary>
+                /// <typeparam name="TState"></typeparam>
+                /// <param name="logLevel"></param>
+                /// <param name="eventId"></param>
+                /// <param name="state"></param>
+                /// <param name="exception"></param>
+                /// <param name="formatter"></param>
+                public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
+                {
+                    if (logLevel >= LogLevel.Error)
+                    {
+                        logLevel = LogLevel.Warning;
+                    }
+                    _inner.Log(logLevel, eventId, state, null, formatter);
+                }
+
+                public bool IsEnabled(LogLevel logLevel)
+                {
+                    return _inner.IsEnabled(logLevel);
+                }
+
+                public IDisposable BeginScope<TState>(TState state)
+                {
+                    return _inner.BeginScope(state);
+                }
+            }
+        }
     }
 }

src/Microsoft.Azure.SignalR.Common/ServiceConnections/ServiceConnectionBase.cs

@@ -525,17 +525,17 @@ private void AbortConnection()
         private static class Log
         {
             // Category: ServiceConnection
-            private static readonly Action<ILogger, Exception> _failedToWrite =
-                LoggerMessage.Define(LogLevel.Error, new EventId(1, "FailedToWrite"), "Failed to send message to the service.");
+            private static readonly Action<ILogger, string, Exception> _failedToWrite =
+                LoggerMessage.Define<string>(LogLevel.Error, new EventId(1, "FailedToWrite"), "Failed to send message to the service: {message}");
 
             private static readonly Action<ILogger, string, Exception> _failedToConnect =
-                LoggerMessage.Define<string>(LogLevel.Error, new EventId(2, "FailedToConnect"), "Failed to connect to the service: {message}.");
+                LoggerMessage.Define<string>(LogLevel.Error, new EventId(2, "FailedToConnect"), "Failed to connect to the service, will retry after the back off period. Error detail: {message}.");
 
             private static readonly Action<ILogger, Exception> _errorProcessingMessages =
                 LoggerMessage.Define(LogLevel.Error, new EventId(3, "ErrorProcessingMessages"), "Error when processing messages.");
 
             private static readonly Action<ILogger, string, Exception> _connectionDropped =
-                LoggerMessage.Define<string>(LogLevel.Error, new EventId(4, "ConnectionDropped"), "Connection {ServiceConnectionId} to the service was dropped.");
+                LoggerMessage.Define<string>(LogLevel.Error, new EventId(4, "ConnectionDropped"), "Connection to the service was dropped, probably caused by network instability or service restart. Will try to reconnect after the back off period. Id: {ServiceConnectionId}");
 
             private static readonly Action<ILogger, Exception> _failedToCleanupConnections =
                 LoggerMessage.Define(LogLevel.Error, new EventId(5, "FailedToCleanupConnection"), "Failed to clean up client connections.");
@@ -617,19 +617,16 @@ private static class Log
 
             public static void FailedToWrite(ILogger logger, Exception exception)
             {
-                _failedToWrite(logger, exception);
+                _failedToWrite(logger, exception.Message, null);
             }
 
             public static void FailedToConnect(ILogger logger, Exception exception)
             {
                 var message = exception.Message;
                 var baseException = exception.GetBaseException();
-                if (baseException != null)
-                {
-                    message += " " + baseException.Message;
-                }
+                message += ". " + baseException.Message;
 
-                _failedToConnect(logger, message, exception);
+                _failedToConnect(logger, message, null);
             }
 
             public static void ErrorProcessingMessages(ILogger logger, Exception exception)

src/Microsoft.Azure.SignalR/ServerConnections/ServiceConnection.Log.cs

@@ -14,8 +14,8 @@ private static class Log
             private static readonly Action<ILogger, Exception> _failedToCleanupConnections =
                 LoggerMessage.Define(LogLevel.Error, new EventId(5, "FailedToCleanupConnection"), "Failed to clean up client connections.");
 
-            private static readonly Action<ILogger, Exception> _errorSendingMessage =
-                LoggerMessage.Define(LogLevel.Error, new EventId(6, "ErrorSendingMessage"), "Error while sending message to the service.");
+            private static readonly Action<ILogger, string, Exception> _errorSendingMessage =
+                LoggerMessage.Define<string>(LogLevel.Error, new EventId(6, "ErrorSendingMessage"), "Error while sending message to the service, the connection carrying the traffic is dropped. Error detail: {message}");
 
             private static readonly Action<ILogger, string, Exception> _sendLoopStopped =
                 LoggerMessage.Define<string>(LogLevel.Error, new EventId(7, "SendLoopStopped"), "Error while processing messages from {TransportConnectionId}.");
@@ -51,7 +51,7 @@ public static void FailedToCleanupConnections(ILogger logger, Exception exceptio
 
             public static void ErrorSendingMessage(ILogger logger, Exception exception)
             {
-                _errorSendingMessage(logger, exception);
+                _errorSendingMessage(logger, exception.Message, exception);
             }
 
             public static void SendLoopStopped(ILogger logger, string connectionId, Exception exception)