How to indicate errors with ChannelReader<T> ?

[Kikimora]

SignalR does not report errors correctly with streaming methods. My code below throws error in 'GetOrAddObservable' with some message. I receive exception on client but it does not have my message, instead it has some generic error message like 'something went wrong on server'.

public ChannelReader<ArraySegment<TradeInfo>> Trades(string instrument)
{
   return _tradeData.GetOrAddObservable(instrument).AsChannelReader();
}

So I tried this instead with same result.

        public ChannelReader<ArraySegment<TradeInfo>> Trades(string instrument)
        {
            try
            {
                return _tradeData.GetOrAddObservable(instrument).AsChannelReader();
            }
            catch (Exception e)
            {
                var cr = Channel.CreateBounded<ArraySegment<TradeInfo>>(1);
                var completed = cr.Writer.TryComplete(new ErrorException(new Error("instrument not found")));
                return cr;
            }
        }

This is my client side code which receives this error.

        public static IObservable<T> AsObservable<T>(this ChannelReader<T> reader)
        {
            var subject = new Subject<T>();
            Task.Run(async () =>
            {
                try
                {
                    Log.Debug("Waiting for WebSocket data");
                    while (await reader.WaitToReadAsync())
                    {
                        Log.Debug("Got WebSocket data");
                        while (reader.TryRead(out var item))
                        {
                            Log.Debug("Read item from WebSocket {item}", item);
                            subject.OnNext(item);
                        }
                    }
                }
                catch (Exception e)
                {
                    Log.Error(e, "WebSocket read failed");
                    subject.OnError(e); //<-- I'd like to have more meaningful error message here
                    throw;
                }
                finally
                {
                    subject.OnCompleted();
                }
            });
            return subject;
        }

AsChannelReader copied from here - https://github.com/aspnet/SignalR/blob/master/samples/SignalRSamples/ObservableExtensions.cs

• Versions of Server-Side NuGet Packages: 1.0.1
• Versions of Client-Side NuGet/NPM Packages: 1.0.1
• Are you using the C# client or the JavaScript client: C#
• The Server you are using (Kestrel/HttpSysServer/IIS/IIS Express/Azure Web App/etc.): TestServer
• The Operating System on the Server (Windows/Linux/macOS): macOS
• The Operating System on the Client (Windows/Linux/macOS): macOS

[BrennanConroy]

By default SignalR will not send the exception message to clients because they can contain sensitive information. You can change this behavior by setting EnableDetailedErrors to true in the server configuration, see https://docs.microsoft.com/en-us/aspnet/core/signalr/configuration?view=aspnetcore-2.1#configure-server-options

In 2.2 we have enabled apps to throw a HubException to allow the apps to send an actual error message to clients without globally setting EnableDetailedErrors.

[Kikimora]

@BrennanConroy Error message is lost even with HubException. Please see below code and results.

This is my server code

        public ChannelReader<ArraySegment<TradeInfo>> Trades(string instrument)
        {
            try
            {
                return _tradeData.GetOrAddObservable(instrument).AsChannelReader();
            }
            catch (Exception e)
            {
                throw new HubException(e.Message);
            }
        }

This is what I see on server
[20:27:59.356496 125 0HLF5O4VPJK63 ERR]
Microsoft.AspNetCore.SignalR.Internal.DefaultHubDispatcher Failed to invoke hub method 'Trades'.
Microsoft.AspNetCore.SignalR.HubException: instrument not found
at MyExchange.MarketData.MarketInfoHub.Trades(String instrument) in /Users/averbin/Projects/tradeio/api/exchange/MarketData.WS/src/MarketInfoHub.cs:line 60

And this is what I got on client
[20:25:43.796629 060 ERR]
Microsoft.AspNetCore.SignalR.HubException: An unexpected error occurred invoking 'Trades' on the server.
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

[BrennanConroy]

Yeah, like I said, it's fixed in 2.2 (SignalR 1.1), you're using 1.0.1 so you won't have the change.

[Kikimora]

Any plans to release SignalR 1.1 as pre release nuget package?

[BrennanConroy]

We have our nightly builds at https://dotnet.myget.org/feed/aspnetcore-dev
For example, the lastest SignalR build is https://dotnet.myget.org/feed/aspnetcore-dev/package/nuget/Microsoft.AspNetCore.SignalR/1.1.0-preview1-34640

[DylanDmitri]

I was confused by these generic errors a couple of days ago, and had to search a bit to find the EnableDetailedErrors field. Maybe it would be useful for the generic responses to have an instructional snippet, like "For more information, set EnableDetailedErrors on the server."?

[aspnet-hello]

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