Edge WebAssembly &
Proxy-Wasm Gateways
Low-latency engineering notes on compiling Rust to Wasm, preventing linear memory boundary leaks, streaming AOT instantiations, and in-process Envoy/Caddy filter routing.
Wasm Linear Memory & Allocator Sandbox
Simulate heap allocations, memory leaks, and pointer fragmentation across the FFI bridge.
Allocator Controls
Core WebAssembly Edge Architectural Patterns
Critical production considerations when executing compiled binaries inside low-latency edge workers.
Linear Memory Leaks
Returning complex buffers (like Strings) to JavaScript via raw pointers without explicit host-directed deallocation leads to uncollectable byte arrays and OOM edge worker restarts.
#[no_mangle]
pub extern "C" fn alloc_str() -> *mut u8 {
// std::mem::forget(s) causes memory leak!
}
Streaming Compilation
Loading .wasm binaries synchronously blocks the isolate thread. Using WebAssembly.instantiateStreaming lets the runtime compile bytecode byte-by-byte as it arrives over the network socket.
const { instance } = await
WebAssembly.instantiateStreaming(
fetch("router.wasm"), imports
);
Proxy-Wasm In-Process Filters
Inject custom routing and auth logic directly into Envoy or Caddy data planes via the proxy-wasm ABI without paying high latency penalties for external sidecars.
impl HttpContext for RouteFilter {
fn on_http_request_headers(...) {
// Intercept without network jump
}
}
WebAssembly Execution Laboratory
Live browser-side tests for edge routing logic, compilation lifecycles, and ABI challenges.
> Edge Router & Filter Sandbox
> Streaming Pipeline Simulator
Simulate how V8 compiles the binary while network bytes are still arriving.
> Compute Benchmark: JS (JIT) vs Wasm
Compare simulated execution cycles for heavy image processing algorithms.
> FFI Challenge: String Decoding
How does JavaScript correctly decode a string returned from Wasm linear memory?
let ptr = wasm.get_string();
let mem = new Uint8Array(wasm.memory.buffer);
let str = new TextDecoder().decode(mem.subarray(ptr, ???));
Ecosystem Repositories & Standards
Foundational runtimes, SDKs, and system interface specifications.
rustwasm/wasm-pack
The one-stop CLI tool for compiling, optimizing, and packaging Rust-generated WebAssembly for web and edge distributions.
bytecodealliance/wasmtime
Fast, secure JIT/AOT standalone runtime for WebAssembly & WASI, powering modern serverless cloud infrastructure.
proxy-wasm/rust-sdk
WebAssembly for Proxies (ABI). Write ultra-low-latency filters for Envoy, Nginx, and edge ingress gateways.
WebAssembly/WASI
The WebAssembly System Interface. A modular standard for system calls (filesystem, clocks, random) outside the browser.