Kestrel Web Server: Understanding and Optimizing Performance

Kestrel is a cross-platform web server for .NET Core, it’s built-in web server for .NET Core, it’s highly performant and can handle high-throughput web traffic. In this article, we will explore the basics of Kestrel, how to configure and tune it for improved performance, and how to integrate it with reverse proxies and load balancers for scalability.

Configuring and Tuning Kestrel for Improved Performance

Kestrel is a high-performance web server for .NET Core, but to get the most out of it, you need to configure and tune it correctly. In this chapter, we will explore some of the best practices for configuring and tuning Kestrel to improve its performance.

The first step in configuring Kestrel is to set the appropriate server limits. This includes setting the maximum number of connections, the maximum number of concurrent requests, and the maximum request body size. These limits help to prevent overloading the server and can be set using the KestrelServerOptions class.

Another important aspect of configuring Kestrel is to set the appropriate thread count. By default, Kestrel uses a thread pool, which is a pool of worker threads that handle incoming requests. The number of threads in the pool can be adjusted to match the number of CPU cores available on the server. This can be done by setting the MaxConcurrentConnections and MaxConcurrentUpgradedConnections properties on the KestrelServerOptions class.

In addition to configuring Kestrel, it’s also important to tune it for improved performance. One way to do this is to use the IISIntegration service, which can be used to offload some of the processing to the IIS server, leaving Kestrel to handle only the most critical tasks. Another way to tune Kestrel is to use the UseLibuv option, which can be used to improve performance on Linux and macOS.

Another important aspect of tuning Kestrel is to set the appropriate buffer size. When a request is received, Kestrel reads the data into a buffer before processing it. By setting the appropriate buffer size, you can reduce the number of times Kestrel needs to read the data, which can improve performance.

It’s also important to keep track of the performance of your Kestrel server using metrics and logs. This can help you identify and troubleshoot any performance issues that may arise. The middleware that ships with ASP.NET Core can be used to gather request and response metrics, and it can be configured to send the data to an external service such as Azure Application Insights or Prometheus.

In conclusion, configuring and tuning Kestrel for improved performance is essential to ensure the quality and reliability of your application. By setting the appropriate server limits, adjusting the thread count, using IISIntegration, setting the appropriate buffer size, and monitoring performance, you can ensure that Kestrel is running at optimal performance.

Integrating Kestrel with Reverse Proxies and Load Balancers for Scalability

Kestrel is a high-performance web server for .NET Core, but as your application grows, you may need to scale it to handle more traffic. One way to achieve this is to integrate Kestrel with reverse proxies and load balancers.

A reverse proxy is a server that sits in front of your application and acts as an intermediary between the client and the application. It can be used to handle tasks such as SSL termination, caching, and routing. Common reverse proxies include Nginx, Apache, and IIS. Integrating Kestrel with a reverse proxy allows you to offload these tasks and improve the performance of your application.

A load balancer is a server that distributes incoming traffic across multiple servers. This allows you to scale your application horizontally by adding more servers as needed. Common load balancers include HAProxy, AWS Elastic Load Balancer, and Azure Load Balancer. Integrating Kestrel with a load balancer allows you to distribute the load of your application across multiple servers, improving its scalability.

When integrating Kestrel with a reverse proxy or load balancer, it’s important to configure Kestrel to listen on a private IP address or a unix domain socket. This is because reverse proxies and load balancers typically handle incoming traffic on the public IP address. Additionally, you should configure the reverse proxy or load balancer to forward traffic to the appropriate ports and IP addresses.

It’s also important to note that when using a reverse proxy or load balancer, you will lose the ability to access the original client IP address, since the proxy or balancer will use its own IP address when forwarding the request. To overcome this issue, you can use headers like X-Forwarded-For or Forwarded to pass on the original client IP address information.

In summary, integrating Kestrel with reverse proxies and load balancers can be an effective way to scale your application and handle more traffic. By offloading tasks such as SSL termination, caching, and routing to a reverse proxy and distributing the load across multiple servers with a load balancer, you can improve the scalability and performance of your application. When using Kestrel with a reverse proxy or load balancer, it’s important to configure Kestrel to listen on a private IP or UNIX domain socket, and configure the proxy or load balancer to forward traffic to the appropriate ports and IP addresses. In addition, it’s important to monitor the performance of your application after it’s integrated with a reverse proxy or load balancer to ensure that it’s running at optimal performance and to identify and troubleshoot any issues that may arise.