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diff --git a/docs/runtime/workers.md b/docs/runtime/workers.md new file mode 100644 index 000000000..0418f057e --- /dev/null +++ b/docs/runtime/workers.md @@ -0,0 +1,54 @@ +## Workers + +Deno supports +[`Web Worker API`](https://developer.mozilla.org/en-US/docs/Web/API/Worker/Worker). + +Workers can be used to run code on multiple threads. Each instance of `Worker` +is run on a separate thread, dedicated only to that worker. + +Currently Deno supports only `module` type workers; thus it's essential to pass +`type: "module"` option when creating new worker: + +```ts +// Good +new Worker("./worker.js", { type: "module" }); + +// Bad +new Worker("./worker.js"); +new Worker("./worker.js", { type: "classic" }); +``` + +### Using Deno in worker + +**UNSTABLE**: This feature is unstable and requires `--unstable` flag + +By default `Deno` namespace is not available in worker scope. + +To add `Deno` namespace pass `deno: true` option when creating new worker: + +```ts +// main.js +const worker = new Worker("./worker.js", { type: "module", deno: true }); +worker.postMessage({ filename: "./log.txt" }); + +// worker.js +self.onmessage = async (e) => { + const { filename } = e.data; + const text = await Deno.readTextFile(filename); + console.log(text); + self.close(); +}; + +// log.txt +hello world +``` + +```shell +$ deno run --allow-read --unstable main.js +hello world +``` + +When `Deno` namespace is available in worker scope; the worker inherits parent +process permissions (the ones specified using `--allow-*` flags). + +We intend to make permissions configurable for workers. |