return data progressively from ServiceStack API - servicestack

Question

Currently my app returns data by MemoryStream, the problem is
the size of data could be large than 500MB, and that takes up much memory before return.
I am seeking for a way to return the data progressively.
For example, flush the output for every 1MB.
First I tried IPartialWriter
public class ViewRenderResult : IPartialWriter
{
public void WritePartialTo(IResponse response)
{
response.Write("XXX");
}
public bool IsPartialRequest { get { return true; } }
}
response.Write can only be called for one time.
Then I found IStreamWriter
public interface IStreamWriter
{
void WriteTo(Stream responseStream);
}
I doubt it caches all data before returining.
Please can anyone clarify it?

Answer 1

This previous answer shows different response types ServiceStack supports, e.g. you can just return a Stream or write to the base.Response.OutputStream directly from within your Service.
These ImageServices also shows the different ways you can write a binary response like an Image to the response stream, e.g. here's an example of using a custom IStreamWriter which lets you control how to write to the Response OutputStream:
//Your own Custom Result, writes directly to response stream
public class ImageResult : IDisposable, IStreamWriter, IHasOptions
{
private readonly Image image;
private readonly ImageFormat imgFormat;
public ImageResult(Image image, ImageFormat imgFormat = null)
{
this.image = image;
this.imgFormat = imgFormat ?? ImageFormat.Png;
this.Options = new Dictionary<string, string> {
{ HttpHeaders.ContentType, this.imgFormat.ToImageMimeType() }
};
}
public void WriteTo(Stream responseStream)
{
using (var ms = new MemoryStream())
{
image.Save(ms, imgFormat);
ms.WriteTo(responseStream);
}
}
public void Dispose()
{
this.image.Dispose();
}
public IDictionary<string, string> Options { get; set; }
}
Which you can return in your Service with:
public object Any(ImageAsCustomResult request)
{
var image = new Bitmap(100, 100);
using (var g = Graphics.FromImage(image))
{
g.Clear(request.Format.ToImageColor());
return new ImageResult(image, request.Format.ToImageFormat());
}
}