Recently I was working on a application update service to support application self-update. I choosed Nancyfx to implement the API service.
For the file downloading, we set up a target to support at least 5000 concurrent connections to download files at the same time with 2 cloud web servers behide load banlancer.
Web-server CPU: Quad 2.6 GHz AMD Opteron 6238 Memory: 16GB
Testing sample file: 5.5MB
How it works
At first, to make things work, I used the AsFile() extension method of NancyRequest. As you can imagine, the performance was poor, with high CPU and memory utilization.
To reduce the memory usage, I cached the file content in the memory since there is small amount of files and no large files. To impove the CPU usage and support large amount of concurrent connections, I used the async/await pattern to write file content directly the HttpResponse of Asp.Net.
To my surprise the momery usage was still crazy when performaning testing.
After several times of tries, I had a doubt that the issue was coming from Nancyfx. As a comparision, I wrote a HttpHandler that handles the downloading directly.
With this handler, it can support more than 10k concurrent downloadings with 2 Web-servers, and the CPU utilization was about 60%~70% and memory usage was low. It seemed the bottleneck was the network bandwidth.