Wasm core dumps and debugging Rust in Cloudflare Workers

This blog post by Francisco Santos and Pedro Henrique Mendes discusses debugging WebAssembly (Wasm) applications using a tool called wasm-coredump. The article explains that while traditional JavaScript error reporting tools like Sentry can provide information about the state of an application, they don't offer much help when dealing with Wasm exceptions due to its isolated and efficient design. To address this issue, Francisco and Pedro introduced wasm-coredump, a tool designed specifically for debugging WebAssembly applications using Cloudflare Workers. The article explains how the core dump of a process is a snapshot that contains information about the application's state at the time it crashed or encountered an error, making it invaluable for debugging purposes. The authors then introduce the concept of "Rust on Workers," where Rust applications are compiled into WebAssembly to run on Cloudflare Workers. They provide code examples and diagrams to demonstrate how wasm-coredump can be used with Sentry to capture core dumps from Wasm exceptions, allowing developers to see a backtrace that includes the source file name, line number, variable names, types, and values of Rust functions. The article also discusses the challenges of generating large WebAssembly binaries when adding DWARF debugging information, which can make it difficult for them to fit within Cloudflare Workers' size limits. To address this issue, they introduce a tool called debuginfo-split that strips out the debugging information from Wasm binaries and saves it in separate files called "debug-{UUID}.wasm," reducing their sizes significantly. Overall, Francisco Santos and Pedro Henrique Mendes' blog post provides an insightful look into debugging WebAssembly applications using wasm-coredump and offers practical solutions for developers to improve their debugging processes when working with Wasm in Cloudflare Workers or other platforms. In terms of key points: 1. Traditional JavaScript error reporting tools like Sentry struggle with providing useful information about the state of a WebAssembly application during an exception, mainly due to its isolated and efficient design. 2. The wasm-coredump tool allows developers to capture core dumps from Wasm exceptions in their applications running on Cloudflare Workers, providing valuable debugging insights like backtraces that include source file names, line numbers, variable names, types, and values of Rust functions. 3. To use wasm-coredump with Sentry for WebAssembly exception reporting, the authors provide code examples and detailed explanations on how to configure both services correctly. 4. The article also discusses challenges related to generating large Wasm binaries when adding DWARF debugging information, which can make it difficult for them to fit within Cloudflare Workers' size limits. They introduce a tool called debuginfo-split that addresses this problem by stripping out the debugging information and saving it in separate files. 5. The authors encourage readers to provide feedback or contribute improvements via their Discord, Community forum, or GitHub repositories for wasm-coredump, debuginfo-split, and related tools. Reference(s): https://blog.cloudflare.com/debugging-wasm-exceptions/```