inngest/helpers/stream.cjs

Official SDK for Inngest.com. Inngest is the reliability layer for modern applications. Inngest combines durable execution, events, and queues into a zero-infra platform with built-in observability.

const require_strings = require('./strings.cjs');

//#region src/helpers/stream.ts
/**
* Creates a {@link ReadableStream} that sends a `value` every `interval`
* milliseconds as a heartbeat, intended to keep a stream open.
*
* Returns the `stream` itself and a `finalize` function that can be used to
* close the stream and send a final value.
*/
const createStream = (opts) => {
	/**
	* We need to resolve this promise with both the stream and the `finalize`
	* function, but having them both instantiated synchronously is difficult, as
	* we need access to the stream's internals too.
	*
	* We create this cheeky deferred promise to grab the internal `finalize`
	* value. Be warned that simpler solutions may appear to compile, but fail at
	* runtime due to variables not being assigned; make sure to test your code!
	*/
	let passFinalize;
	const finalizeP = new Promise((resolve) => {
		passFinalize = resolve;
	});
	const interval = opts?.interval ?? 3e3;
	const value = opts?.value ?? " ";
	return new Promise(async (resolve, reject) => {
		try {
			resolve({
				stream: new ReadableStream({ start(controller) {
					const encoder = new TextEncoder();
					const heartbeat = setInterval(() => {
						controller.enqueue(encoder.encode(value));
					}, interval);
					const finalize = (data) => {
						clearInterval(heartbeat);
						Promise.resolve(data).then((resolvedData) => {
							controller.enqueue(encoder.encode(require_strings.stringify(resolvedData)));
							controller.close();
						});
					};
					passFinalize(finalize);
				} }),
				finalize: await finalizeP
			});
		} catch (err) {
			reject(err);
		}
	});
};

//#endregion
exports.createStream = createStream;
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