OpenWorkers Runtime Boa

Pure Rust JavaScript runtime for serverless workers, built on Boa.

Quick Start

use openworkers_runtime_boa::{Event, HttpMethod, HttpRequest, RequestBody, Script, Worker};
use std::collections::HashMap;

let script = Script::new(r#"
    addEventListener('fetch', event => {
        event.respondWith(new Response('Hello from Boa!'));
    });
"#);

let mut worker = Worker::new(script, None).await?;

let req = HttpRequest {
    method: HttpMethod::Get,
    url: "http://localhost/".to_string(),
    headers: HashMap::new(),
    body: RequestBody::None,
};

let (task, rx) = Event::fetch(req);
worker.exec(task).await?;

let response = rx.await?;

Worker::new runs with DefaultOps, which rejects every outbound operation. Pass a real OperationsHandler through Worker::new_with_ops to serve fetch() from the host.

Supported

• 100% Rust - no C/C++ dependencies, builds anywhere
• Fast cold start - no JIT warmup
• Events - addEventListener('fetch') and addEventListener('scheduled')
• Web APIs - console, timers, fetch, Request, Response, Headers, URL, URLSearchParams, Blob, File, FormData, AbortController, ReadableStream, TextEncoder/TextDecoder, atob/btoa, structuredClone, queueMicrotask. console, timers, fetch, AbortController, URL, TextEncoder/TextDecoder, atob/btoa and structuredClone come from boa_runtime; the rest are ours
• Logs - console and uncaught handler errors go to the OperationsHandler
• Request lifetime - the response goes out as soon as respondWith settles, and the timers and fetches still pending behind it are dropped
• Crypto - getRandomValues, randomUUID, subtle.digest
• Async/await - full Promise support

Not supported

• CPU and memory limits - only max_wall_clock_time_ms is enforced
• Bindings - env and the KV/storage/database/worker bindings are not exposed to JS
• ES modules - only addEventListener, not export default { fetch }
• Streaming bodies - RequestBody::Stream and ResponseBody::Stream are not read
• event.waitUntil - the fetch event has no waitUntil
• Binary bodies - request and response bodies round-trip as lossy UTF-8, so formData() reads application/x-www-form-urlencoded and rejects multipart
• Snapshots - Boa has no equivalent of the V8 startup snapshot

Testing

cargo test

SSR benchmark

Renders a real 303 KB SvelteKit bundle, the openworkers-website build:

cargo run --release --features ssr-bench --example ssr_bench

The output is byte-identical to the same fixture rendered on V8 (sha256 2ccbe4f9d1c98441dbe07ee2307597719adbcfbe5e181aa9a03fcd5d572a584c).

Conformance

Runs the 17 SvelteKit scenarios of openworkers-conformance and diffs status, headers in emission order and body bytes against the responses recorded on openworkers-runtime-v8:

cargo run --release --features conformance --example conformance

16 of 17 match byte for byte. urlencoded-plus differs on purpose: the urlencoded parser decodes + to a space, which the recorded oracle does not.

Status

See TODO.md for the roadmap.

License

MIT