Blazor Server and Azure SignalR File Download Troubleshoot

Question

We are trying out Azure SignalR with Blazor Server (dotnet 6), we followed the tutorial from this documentation:

https://learn.microsoft.com/en-us/aspnet/core/blazor/file-downloads?view=aspnetcore-7.0

Building the file functionality (using the stream method) worked without using Azure SignalR. But when we set up the Azure SignalR, the file download is broken (the rest of the app seems to be working fine though), the browser isn't reporting any error and the WebSocket connection seems to be fine. We are not sure why this is. Thank you!

Answer 1

UPDATE

Please upgrading the Azure SignalR SDK to the latest version 1.12.2 ( Change the version from the project file

<PackageReference Include="Microsoft.Azure.SignalR" Version="1.21.2" />) 

It provides better stability and provide more logs if something is wrong.

When uses client stream to download large files (say over 200MB), currently your client has high possibility hit the service SlowClient throttling rule

(buffering 16 data frames with max 1MB size per client) and the client will be closed with SlowClient reason by the service.

For now we should use the "download a file via a URL" solution if the size is larger than 100MB.

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It's very interesting and I also test in my local by using this repo. And find that blazor server side uses SignalR and has its data transfer (buffer) limitations.

You can adjust the code below according to your actual needs.

        builder.Services.AddSignalR(options =>
        {
            options.EnableDetailedErrors = true;
            // According your needs
            options.MaximumReceiveMessageSize = 102400000; // 100 MB
        });
        ...
        // According your needs
        app.MapHub<MainHub>("/mainhub", options => {
            options.ApplicationMaxBufferSize = 102400000; // 100 MB
            options.TransportMaxBufferSize = 102400000; // 100 MB
        });

Related Link

Buffer management