CloudFront function for HTTP upgrade request

CloudFront Functions can indeed be used for HTTP upgrade requests, including WebSocket connection requests. This makes them suitable for your use case of dynamically selecting an origin based on HTTP header parameters in upgrade requests.

CloudFront Functions are designed to run at the edge and can modify requests before they reach the origin. This means you can use them to examine the headers of an HTTP upgrade request and route the WebSocket connection to a specific backend host based on criteria like a chat group ID.

To implement this, you would create a CloudFront Function that runs on the viewer request event. This function would examine the relevant HTTP headers in the upgrade request, such as the chat group ID you mentioned. Based on this information, the function can then modify the request to route it to the appropriate origin for that specific chat group.

However, it's important to note that to make the CloudFront-specific request headers (like the ones containing information about the viewer's country or device type) available to your function, you need to explicitly include them in your distribution's configuration. This is done through either a cache policy or an origin request policy, depending on whether you want these headers to affect caching behavior or not.

By leveraging CloudFront Functions in this way, you can create a dynamic routing system for your WebSocket connections, ensuring that clients from specific chat groups are directed to the appropriate backend hosts. This approach allows for efficient management of WebSocket connections while taking advantage of CloudFront's edge computing capabilities.
Sources
Customize at the edge with CloudFront Functions - Amazon CloudFront
How do I make CloudFront request headers available in my edge compute functions? | AWS re:Post
Use various origins with CloudFront distributions - Amazon CloudFront