OpenWorkers Runtime JSC

JavaScriptCore-based JavaScript runtime for serverless workers, built on openworkers-jsc.

Quick Start

use openworkers_runtime_jsc::{Worker, Script, Event};

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

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

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

Features

• Streaming - ReadableStream with backpressure
• Web APIs - fetch, setTimeout, Response, Request, Headers, URL, console
• Async/await - Full Promise support
• Text encoding - TextEncoder, TextDecoder
• Base64 - atob, btoa
• Crypto - getRandomValues, randomUUID, SubtleCrypto
• Invoke binding - with the invoke feature, env.<NAME>.invoke(command, args) calls OperationsHandler::handle_binding_invoke with JSON arguments; the other binding types are not served

Web APIs

API	Status
console	yes
fetch	yes
setTimeout / setInterval	yes
Promise / queueMicrotask	yes
Request / Response / Headers	yes
ReadableStream	yes
URL / URLSearchParams	yes
TextEncoder / TextDecoder	yes
atob / btoa	yes
crypto.getRandomValues	yes
crypto.randomUUID	yes
crypto.subtle.digest	SHA-1, SHA-256, SHA-384, SHA-512
crypto.subtle.sign / verify	HMAC, ECDSA P-256, RSA PKCS#1 v1.5
crypto.subtle.importKey	raw, pkcs8, spki
crypto.subtle.generateKey	ECDSA P-256
Blob / File / FormData	no
AbortController	no

See TODO.md for planned features.

JavaScriptCore builds

Feature	JavaScriptCore
system (default)	JavaScriptCore.framework of macOS
static	the pinned static JSC of oven-sh/WebKit, macOS arm64 only (wins over system)

• With the JIT, the CPU limit needs polling traps: call openworkers_jsc::init with polling_traps before other threads start, or set JSC_usePollingTraps=true. The system framework runs the JIT only in a binary with the com.apple.security.cs.allow-jit entitlement; the static build always runs it. With the JIT and without polling traps, the watchdog cuts some loops late or never: an empty loop and a loop of Date.now() calls on the system framework, a loop of Date.now() calls on the static build. The check at the first worker runs these loops, and refuses every worker when a cut comes late.
• static: the WTF timers (GC, sweeper, FinalizationRegistry callbacks) go to a host per thread, which the worker fires from its event loop under its CPU budget.

Testing

cargo test --features invoke
JSC_usePollingTraps=true cargo test --features invoke,static

License

MIT