Cloudflare Workflows

Cloudflare Workflows

Workflows provide durable multi-step execution for Workers. Steps persist state, survive restarts, support retries, and can sleep for days.

Quick Start

Create Workflow

// src/index.ts
import { WorkflowEntrypoint, WorkflowStep, WorkflowEvent } from "cloudflare:workers";

interface Env {
  MY_WORKFLOW: Workflow;
}

interface Params {
  userId: string;
  action: string;
}

export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    const user = await step.do("fetch user", async () => {
      const resp = await fetch(`https://api.example.com/users/${event.payload.userId}`);
      return resp.json();
    });

    await step.sleep("wait before processing", "1 hour");

    const result = await step.do("process action", async () => {
      return { processed: true, user: user.id };
    });

    return result; // Available in instance.status().output
  }
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const instance = await env.MY_WORKFLOW.create({
      params: { userId: "123", action: "activate" },
    });
    return Response.json({ instanceId: instance.id });
  },
};

wrangler.jsonc

{
  "name": "my-workflow-worker",
  "main": "src/index.ts",
  "workflows": [
    {
      "name": "my-workflow",
      "binding": "MY_WORKFLOW",
      "class_name": "MyWorkflow"
    }
  ]
}

Deploy

npx wrangler deploy

Core Concepts

WorkflowEntrypoint

export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    // Workflow logic with steps
    return optionalResult;
  }
}

WorkflowEvent

interface WorkflowEvent<T> {
  payload: Readonly<T>; // Immutable input params
  timestamp: Date; // Creation time
  instanceId: string; // Unique instance ID
}

Warning: Event payload is immutable. Changes are NOT persisted across steps. Return state from steps instead.

WorkflowStep

interface WorkflowStep {
  do<T>(name: string, callback: () => Promise<T>): Promise<T>;
  do<T>(name: string, config: StepConfig, callback: () => Promise<T>): Promise<T>;
  sleep(name: string, duration: Duration): Promise<void>;
  sleepUntil(name: string, timestamp: Date | number): Promise<void>;
  waitForEvent<T>(name: string, options: WaitOptions): Promise<T>;
}

See api.md for full type definitions.

Steps

Basic Step

const result = await step.do("step name", async () => {
  const response = await fetch("https://api.example.com/data");
  return response.json(); // State persisted
});

Step with Config

const data = await step.do(
  "call external API",
  {
    retries: {
      limit: 10,
      delay: "30 seconds",
      backoff: "exponential",
    },
    timeout: "5 minutes",
  },
  async () => {
    return await externalApiCall();
  }
);

Default Step Config

const defaultConfig = {
  retries: {
    limit: 5,
    delay: 10000, // 10 seconds
    backoff: "exponential",
  },
  timeout: "10 minutes",
};

Sleep & Scheduling

Relative Sleep

await step.sleep("wait before retry", "1 hour");
await step.sleep("short pause", 5000); // 5 seconds (ms)

Duration units: second, minute, hour, day, week, month, year.

Sleep Until Date

const targetDate = new Date("2024-12-31T00:00:00Z");
await step.sleepUntil("wait until new year", targetDate);

// Or with timestamp
await step.sleepUntil("wait until launch", Date.parse("24 Oct 2024 13:00:00 UTC"));

Maximum sleep: 365 days.

Note: step.sleep and step.sleepUntil do NOT count towards the 1024 steps limit.

Wait for Events

Wait in Workflow

const approval = await step.waitForEvent<{ approved: boolean }>("wait for approval", {
  type: "user_approval",
  timeout: "7 days",
});

if (approval.approved) {
  await step.do("proceed", async () => {
    /* ... */
  });
}

Default timeout: 24 hours.

Timeout behavior: Throws error and fails instance. Use try-catch to continue:

try {
  const event = await step.waitForEvent("optional event", { type: "update", timeout: "1 hour" });
} catch (e) {
  // Continue without event
}

Send Event from Worker

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const { instanceId, approved } = await request.json();
    const instance = await env.MY_WORKFLOW.get(instanceId);

    await instance.sendEvent({
      type: "user_approval", // Must match waitForEvent type
      payload: { approved },
    });

    return new Response("Event sent");
  },
};

Event buffering: Events can be sent before Workflow reaches waitForEvent. They are buffered and delivered when the matching step executes.

See events.md for REST API.

Error Handling

NonRetryableError

import { NonRetryableError } from "cloudflare:workflows";

await step.do("validate input", async () => {
  if (!event.payload.data) {
    throw new NonRetryableError("Missing required data");
  }
  return event.payload.data;
});

Catch and Continue

try {
  await step.do("risky operation", async () => {
    await riskyApiCall();
  });
} catch (error) {
  await step.do("handle failure", async () => {
    await sendAlertEmail(error.message);
  });
}

Workflow States

Workflow Bindings

Create Instance

const instance = await env.MY_WORKFLOW.create({
  id: "order-12345", // Optional custom ID (max 100 chars)
  params: { orderId: 12345 },
});
console.log(instance.id);

Create Batch

const instances = await env.MY_WORKFLOW.createBatch([{ params: { userId: "1" } }, { params: { userId: "2" } }, { params: { userId: "3" } }]);
// Up to 100 instances per batch

Get Instance

const instance = await env.MY_WORKFLOW.get("order-12345");

Instance Methods

await instance.pause(); // Pause execution
await instance.resume(); // Resume paused
await instance.terminate(); // Stop permanently
await instance.restart(); // Restart from beginning

const status = await instance.status();
console.log(status.status); // "running", "complete", etc.
console.log(status.output); // Return value from run()
console.log(status.error); // { name, message } if errored

await instance.sendEvent({
  type: "approval",
  payload: { approved: true },
});

Rules of Workflows

✅ DO

• Make steps granular and self-contained
• Return state from steps (only way to persist)
• Name steps deterministically
• await all step calls
• Keep step return values under 1 MiB
• Use idempotent operations in steps
• Base conditions on event.payload or step returns

❌ DON'T

• Store state outside steps (lost on restart)
• Mutate event.payload (changes not persisted)
• Use non-deterministic step names (Date.now(), Math.random())
• Skip await on step calls
• Put entire logic in one step
• Call multiple unrelated services in one step
• Do heavy CPU work in single step

Step State Persistence

// ✅ Good: Return state from step
const userData = await step.do("fetch user", async () => {
  return await fetchUser(userId);
});

// ❌ Bad: State stored outside step (lost on restart)
let userData;
await step.do("fetch user", async () => {
  userData = await fetchUser(userId); // Will be lost!
});

Wrangler Commands

# List instances
wrangler workflows instances list my-workflow

# Describe instance
wrangler workflows instances describe my-workflow --id <instance-id>

# Terminate instance
wrangler workflows instances terminate my-workflow --id <instance-id>

# Trigger new instance
wrangler workflows trigger my-workflow --params '{"key": "value"}'

# Delete Workflow
wrangler workflows delete my-workflow

Limits

Note: Instances in waiting state (sleeping, waiting for event) do NOT count against concurrency limits.

Increase CPU Limit

{
  "limits": {
    "cpu_ms": 300000 // 5 minutes
  }
}

Pricing

Based on Workers Standard pricing:

Storage notes:

• Calculated across all instances (running, sleeping, completed)
• Deleting instances frees storage (updates within minutes)
• Free plan: instance errors if storage limit reached

See pricing.md for details.

Prohibitions

• ❌ Do not mutate event.payload (changes not persisted)
• ❌ Do not store state outside steps
• ❌ Do not use non-deterministic step names
• ❌ Do not exceed 1 MiB per step return
• ❌ Do not skip await on step calls
• ❌ Do not rely on in-memory state between steps

References

• api.md — Full API reference
• events.md — Event handling and REST API
• patterns.md — Saga, approval, reminders
• pricing.md — Billing details

Cross-References (Skills)

• cloudflare-workers — Worker development
• cloudflare-queues — Message queue integration
• cloudflare-r2 — Large state storage
• cloudflare-kv — Key-value references