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Workflows is now Generally Available

Apr 07, 2025, 01:00 PM

Workflows Workers

Workflows is now Generally Available (or "GA"): in short, it's ready for production workloads. Alongside marking Workflows as GA, we've introduced a number of changes during the beta period, including:

• A new waitForEvent API that allows a Workflow to wait for an event to occur before continuing execution.
• Increased concurrency: you can run up to 4,500 Workflow instances concurrently — and this will continue to grow.
• Improved observability, including new CPU time metrics that allow you to better understand which Workflow instances are consuming the most resources and/or contributing to your bill.
• Support for vitest for testing Workflows locally and in CI/CD pipelines.

Workflows also supports the new increased CPU limits that apply to Workers, allowing you to run more CPU-intensive tasks (up to 5 minutes of CPU time per instance), not including the time spent waiting on network calls, AI models, or other I/O bound tasks.

Human-in-the-loop

The new step.waitForEvent API allows a Workflow instance to wait on events and data, enabling human-in-the-the-loop interactions, such as approving or rejecting a request, directly handling webhooks from other systems, or pushing event data to a Workflow while it's running.

Because Workflows are just code, you can conditionally execute code based on the result of a waitForEvent call, and/or call waitForEvent multiple times in a single Workflow based on what the Workflow needs.

For example, if you wanted to implement a human-in-the-loop approval process, you could use waitForEvent to wait for a user to approve or reject a request, and then conditionally execute code based on the result.

JavaScript

import { Workflow, WorkflowEvent } from "cloudflare:workflows";

export class MyWorkflow extends WorkflowEntrypoint {
  async run(event, step) {
    // Other steps in your Workflow
    let event = await step.waitForEvent(
      "receive invoice paid webhook from Stripe",
      { type: "stripe-webhook", timeout: "1 hour" },
    );
    // Rest of your Workflow
  }
}

TypeScript

import { Workflow, WorkflowEvent } from "cloudflare:workflows";

export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    // Other steps in your Workflow
    let event = await step.waitForEvent<IncomingStripeWebhook>("receive invoice paid webhook from Stripe", { type: "stripe-webhook", timeout: "1 hour" })
    // Rest of your Workflow
  }
}

You can then send a Workflow an event from an external service via HTTP or from within a Worker using the Workers API for Workflows:

JavaScript

export default {
  async fetch(req, env) {
    const instanceId = new URL(req.url).searchParams.get("instanceId");
    const webhookPayload = await req.json();

    let instance = await env.MY_WORKFLOW.get(instanceId);
    // Send our event, with `type` matching the event type defined in
    // our step.waitForEvent call
    await instance.sendEvent({
      type: "stripe-webhook",
      payload: webhookPayload,
    });

    return Response.json({
      status: await instance.status(),
    });
  },
};

TypeScript

export default {
  async fetch(req: Request, env: Env) {
    const instanceId = new URL(req.url).searchParams.get("instanceId")
    const webhookPayload = await req.json<Payload>()

    let instance = await env.MY_WORKFLOW.get(instanceId);
    // Send our event, with `type` matching the event type defined in
    // our step.waitForEvent call
    await instance.sendEvent({type: "stripe-webhook", payload: webhookPayload})

    return Response.json({
      status: await instance.status(),
    });
  },
};

Read the GA announcement blog ↗ to learn more about what landed as part of the Workflows GA.