Unable to access the response body

[beukerz]

Describe the bug

In middleware or in a transform the response body is always empty.

To Reproduce

Transform code:

builder.Services.AddReverseProxy()
            .LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"))
            .AddTransforms(context =>
            {
                // stole from https://microsoft.github.io/reverse-proxy/articles/transforms.html#response-body-transforms
                context.AddResponseTransform(async responseContext =>
                {
                    if (responseContext.ProxyResponse != null)
                    {
                        var stream = await responseContext.ProxyResponse.Content.ReadAsStreamAsync();
                        using var reader = new StreamReader(stream);
                        var body = await reader.ReadToEndAsync();
                        Console.WriteLine("Response body: " + body);
                    }
                });
            });

Middleware code:

app.MapReverseProxy(proxyPipeline =>
{
    proxyPipeline.Use(async (httpContext, next) =>
    {
        try
        {
            httpContext.Request.EnableBuffering();
            string requestBody = await new StreamReader(httpContext.Request.Body, Encoding.UTF8).ReadToEndAsync();
            httpContext.Request.Body.Position = 0;
            Console.WriteLine($"Request body: {requestBody}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Exception reading request: {ex.Message}");
        }

        Stream originalBody = httpContext.Response.Body;
        try
        {
            using var memStream = new MemoryStream();
            httpContext.Response.Body = memStream;

            await next(httpContext);

            memStream.Position = 0;
            string responseBody = new StreamReader(memStream).ReadToEnd();

            memStream.Position = 0;
            await memStream.CopyToAsync(originalBody);
            Console.WriteLine("Response body: " + responseBody);
        }
        finally
        {
            httpContext.Response.Body = originalBody;
        }
    });
    proxyPipeline.UseSessionAffinity();
    proxyPipeline.UseLoadBalancing();
    proxyPipeline.UsePassiveHealthChecks();
});

In both situations the body is always an empty string.

Further technical details

• Include the version of the packages you are using
  2.2.0
• The platform (Linux/macOS/Windows)
  Windows

Sample repository

https://github.com/[beukerz/yarpsample](https://github.com/beukerz/yarpsample)

[MihaZupan]

Can you create a minimal runnable example where it doesn't work in your case? The sample code does "work on my machine"™.
What kind of requests are you testing it with?

Note that as-written, the response transform would break the request as the content can't be re-read, but it should still print the body to the console before doing so.

[beukerz]

Can you create a minimal runnable example where it doesn't work in your case? The sample code does "work on my machine"™. What kind of requests are you testing it with?

Note that as-written, the response transform would break the request as the content can't be re-read, but it should still print the body to the console before doing so.

I have added the link to a sample repo (https://github.com/[beukerz/yarpsample](https://github.com/beukerz/yarpsample))

I am sending a simple get request to the weather api.

[MihaZupan]

Do you have a step-by-step for what you've tried that doesn't work?
The route in the sample doesn't match the sample application, but assuming you fix that, it also does work as expected for me.
Is running it through containers necessary to reproduce the issue?

[beukerz]

I just tested running the project without containers and it works. So it seems the issue only exists in containers.

[MihaZupan]

Sounds like a non-YARP issue then. Let me know if we've missed something.