What is proxygen?

Proxygen is a set of C++ libraries that Facebook built to handle HTTP traffic across its internal systems. It forms the foundation for many of Facebook's own HTTP servers, proxies, and clients. The project is open source so that other developers can use the same HTTP infrastructure code. The library supports several versions of the HTTP protocol: HTTP/1.1, HTTP/2, and HTTP/3. HTTP/3 is the newest version of the web's main communication protocol and relies on a transport mechanism called QUIC, which is designed to be faster and more reliable than older approaches. Proxygen's HTTP/3 support is built on top of another Facebook open-source project called mvfst. There are two main levels at which developers interact with the library. The lower level provides detailed control over how connections, requests, and responses are parsed and sent. The higher level, found in the httpserver directory, provides a simpler set of building blocks: a server object, a factory that creates a handler for each incoming request, and a handler class that developers fill in with their own logic. The higher level is the recommended starting point unless fine-grained control is needed. The repository includes several sample programs: an echo server, a server that supports HTTP/2 push, a static file server, a forward proxy, and a command-line HTTP/3 client. These samples show how to wire together the library's components for common use cases. Installation on Ubuntu and macOS is handled by a build script that fetches and compiles the dependencies. It can also be installed via the vcpkg package manager on supported platforms. The project requires at least 3 gigabytes of memory to compile.