Blazor Stream Rendering not working on Azure Web Apps

[darena-pjindal]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Hello - I have a blazor application that has stream rendering activated on multiple pages. It works without any issues locally. I have deployed it to Azure Web app. The page behaves as there is no stream rendering. Is there a particular configuration that we need to use (or not use) to enable stream rendering on Azure web app

Expected Behavior

No response

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version

No response

Anything else?

No response

[javiercn]

@darena-pjindal thanks for contacting us.

• Are you able to make it work with a project created straight out of the template?
• Are you using the default publish settings to Azure Web Apps?
• Is there a public URL where we can see this not working?
• Are you using any middleware that might be buffering the response?

[darena-pjindal]

Hello @javiercn

I created a new blazor web app from scratch and published it to Azure Web app. The only change I made was to increase the delay on the weather page so the steaming is more visible. You can check the deployed site here - https://blazortestds.azurewebsites.net/weather

There were no other changes made to the default template. Here are the settings from visual studio to deploy

Thanks,
Pawan

[darena-pjindal]

Hi @javiercn - I just noticed that if I go directly to the weather page, it does seem to work. However, if I go from the home page to that page, it doesn't seem to work. Our app requires a user to be logged in. Therefore, all our pages (with stream rendering) are viewed from one component to another. Thanks for your help.

[javiercn]

@darena-pjindal thanks for the additional details.

This is likely Azure Websites compressing the response before sending it and buffering to do so

This is likely the culprit.

I think though we've addressed this recently on a servicing release (not sure if it is out yet) so this will be solved in the near future I believe.

[javiercn]

It's scheduled to go into a servicing release #53930

[javiercn]

@darena-pjindal we are closing this issue as a dupe of #52323

You can apply a similar workaround by setting context.Response.Headers.ContentEncoding = "identity"; on the responses. That should prevent IIS from applying compression

[darena-pjindal]

Hi @javiercn - thanks for your help. Can you please share more details on how and where I should set this?

[darena-pjindal]

You can apply a similar workaround by setting context.Response.Headers.ContentEncoding = "identity"; on the responses. That should prevent IIS from applying compression

I figured it out. Just added a middleware to handle that. Copying here if someone else also needs it. Thanks again .

public class PreventCompressionMiddleware
{
private readonly RequestDelegate _next;

public PreventCompressionMiddleware(RequestDelegate next)
{
    _next = next;
}

public async Task Invoke(HttpContext context)
{
    context.Response.OnStarting(() =>
    {
        context.Response.Headers["Content-Encoding"] = "identity";
        return Task.CompletedTask;
    });

    await _next(context);
}

}