Asp.Net HttpClient性能

Question

I'm load/stress testing using Visual Studios load testing project with current users set quite low at 10. The application makes multiple System.Net.Http.HttpClient request to a WebAPI service layer/application (which in some cases calls another WebApi layer/application) and it's only getting around 30 request/second when testing a single MVC4 controller (not parsing dependent requests).

These figures are based on a sample project where no real code is executed at any of the layers other then HttpClient calls and to contruct a new collection of Models to return (so some serialization happening too as part of WebApi). I've tried both with async controller and without and the results seemed pretty similar (slight improvement with async controllers)

Caching the calls obviously increases it dramatically (to around 400 RPS) although the nature of the data and the traffic means that a significant amount of the calls wouldn't be cached in real world scenarios.

Is HttpClient (or HTTP layer in general) simply too expensive or are there some ideas you have around getting higher throughput?

It might be worth noting that on my local development machine this load test also maxes out the CPU. Any ideas or suggestions would be very much appreciated?

Answer 1

HttpClient has a built-in default of 2 concurrent connections.

Have you changed the default?

See this answer

I believe if you chase the deps for HTTPClient, you will find that it relies on the settings for ServicePointManager.

See this link

You can change the default connection limit by calling System.Net.ServicePointManager.DefaultConnectionLimit

Answer 2

You can increase number of concurrent connection for http client. Default connection limit is 2. In order to find optimum connection try the formula 12* number of CPU on your machine.

In code : In code:

ServicePointManager.DefaultConnectionLimit = 48;  

Or In Api.config or web.config file

<system.net>
    <connectionManagement>
      <add address="*" maxconnection="48"/>
    </connectionManagement>
  </system.net>

Check this link for more detail.