Cloudflare Workers Adds Experimental Emscripten Target Support for Native Rust and Tokio

Emscripten Target Integration

Cloudflare has introduced an experimental preview of support for the Emscripten `wasm32-unknown-emscripten` Rust compiler target within the `wasm-bindgen` open-source toolchain. This integration allows for better execution of native Rust code and Tokio-based applications directly on Cloudflare Workers.

The `wasm-bindgen` toolchain powers Rust-based WebAssembly applications on Cloudflare's V8-based Workers Runtime. The effort to enable the Emscripten target was initiated by Google and further developed by Cloudflare engineers.

Enhanced Capabilities for Rust Workers

This new support significantly improves library compatibility for Rust Workers. Emscripten, an open-source WebAssembly compiler toolchain maintained by Google, facilitates running and bridging native code with the web platform.

It virtualizes platform features such as timers, file system operations, and sockets. Cloudflare Workers can support Emscripten by utilizing its Node.js compilation flags, virtualizing these native features on top of existing Node.js APIs.

Tokio Support and Practical Applications

With this update, Rust code built on Tokio's async runtime ecosystem can now be integrated into JavaScript-based host environments using the Emscripten target. This allows for applications like a Rust-native Minecraft server (Pumpkin) to run inside a Durable Object with TCP ingress, using real TCP sockets via Tokio.

Experimental patchsets and example applications are available, demonstrating how to build Emscripten Rust Workers, run the Tokio async runtime in a Worker, and use TCP Sockets on Workers with Emscripten and Tokio.