Inngest Steps

// ❌ WRONG - will run 4 times
export default inngest.createFunction(
  { id: "bad-example", triggers: [{ event: "test" }] },
  async ({ step }) => {
    console.log("This logs 4 times!"); // Outside step = bad
    await step.run("a", () => console.log("a"));
    await step.run("b", () => console.log("b"));
    await step.run("c", () => console.log("c"));
  },
);

// ✅ CORRECT - logs once each
export default inngest.createFunction(
  { id: "good-example", triggers: [{ event: "test" }] },
  async ({ step }) => {
    await step.run("log-hello", () => console.log("hello"));
    await step.run("a", () => console.log("a"));
    await step.run("b", () => console.log("b"));
    await step.run("c", () => console.log("c"));
  },
);

// Basic usage
const result = await step.run("fetch-user", async () => {
  const user = await db.user.findById(userId);
  return user; // Always return useful data
});

// Synchronous code works too
const transformed = await step.run("transform-data", () => {
  return processData(result);
});

// Side effects (no return needed)
await step.run("send-notification", async () => {
  await sendEmail(user.email, "Welcome!");
});

// Duration strings
await step.sleep("wait-24h", "24h");
await step.sleep("short-delay", "30s");
await step.sleep("weekly-pause", "7d");

// Use in workflows
await step.run("send-welcome", () => sendEmail(email));
await step.sleep("wait-for-engagement", "3d");
await step.run("send-followup", () => sendFollowupEmail(email));

const reminderDate = new Date("2024-12-25T09:00:00Z");
await step.sleepUntil("wait-for-christmas", reminderDate);

// From event data
const scheduledTime = new Date(event.data.remind_at);
await step.sleepUntil("wait-for-scheduled-time", scheduledTime);

// Basic event waiting with timeout
const approval = await step.waitForEvent("wait-for-approval", {
  event: "app/invoice.approved",
  timeout: "7d",
  match: "data.invoiceId", // Simple matching
});

// Expression-based matching (CEL syntax)
const subscription = await step.waitForEvent("wait-for-subscription", {
  event: "app/subscription.created",
  timeout: "30d",
  if: "event.data.userId == async.data.userId && async.data.plan == 'pro'",
});

// Handle timeout
if (!approval) {
  await step.run("handle-timeout", () => {
    // Approval never came
    return notifyAccountingTeam();
  });
}

const taskId = "task-" + crypto.randomUUID();

const signal = await step.waitForSignal("wait-for-task-completion", {
  signal: taskId,
  timeout: "1h",
  onConflict: "replace", // Required: "replace" overwrites pending signal, "fail" throws an error
});

// Send signal elsewhere via Inngest API or SDK
// POST /v1/events with signal matching taskId

// Trigger other functions
await step.sendEvent("notify-systems", {
  name: "user/profile.updated",
  data: { userId: user.id, changes: profileChanges },
});

// Multiple events at once
await step.sendEvent("batch-notifications", [
  { name: "billing/invoice.created", data: { invoiceId } },
  { name: "email/invoice.send", data: { email: user.email, invoiceId } },
]);

const computeSquare = inngest.createFunction(
  { id: "compute-square", triggers: [{ event: "calculate/square" }] },
  async ({ event }) => {
    return { result: event.data.number * event.data.number };
  },
);

// Invoke and use result
const square = await step.invoke("get-square", {
  function: computeSquare,
  data: { number: 4 },
});

console.log(square.result); // 16, fully typed!

// For cross-app invocation (when you can't import the function directly):
import { referenceFunction } from "inngest";

const externalFn = referenceFunction({
  appId: "other-app",
  functionId: "other-fn",
});

const result = await step.invoke("call-external", {
  function: externalFn,
  data: { key: "value" },
});

const allProducts = [];
let cursor = null;
let hasMore = true;

while (hasMore) {
  // Same ID "fetch-page" reused - counters handled automatically
  const page = await step.run("fetch-page", async () => {
    return shopify.products.list({ cursor, limit: 50 });
  });

  allProducts.push(...page.products);

  if (page.products.length < 50) {
    hasMore = false;
  } else {
    cursor = page.products[49].id;
  }
}

await step.run("process-products", () => {
  return processAllProducts(allProducts);
});

// Create steps without awaiting
const sendEmail = step.run("send-email", async () => {
  return await sendWelcomeEmail(user.email);
});

const updateCRM = step.run("update-crm", async () => {
  return await crmService.addUser(user);
});

const createSubscription = step.run("create-subscription", async () => {
  return await subscriptionService.create(user.id);
});

// Run all in parallel
const [emailId, crmRecord, subscription] = await Promise.all([
  sendEmail,
  updateCRM,
  createSubscription,
]);

// Parallel steps are optimized by default in v4
export default inngest.createFunction(
  {
    id: "parallel-heavy-function",
    triggers: [{ event: "process/batch" }],
  },
  async ({ event, step }) => {
    const results = await Promise.all(
      event.data.items.map((item, i) =>
        step.run(`process-item-${i}`, () => processItem(item)),
      ),
    );
  },
);

// ⚠️ Promise.race() behavior with v4's optimized parallelism:
// All promises settle before race resolves. Use group.parallel() for true race:
const winner = await group.parallel(async () => {
  return Promise.race([
    step.run("fast-service", () => callFastService()),
    step.run("slow-service", () => callSlowService()),
  ]);
});

// To disable optimized parallelism if needed:
// At the client level: new Inngest({ id: "app", optimizeParallelism: false })
// At the function level: { id: "fn", optimizeParallelism: false, triggers: [...] }

export default inngest.createFunction(
  { id: "process-large-dataset", triggers: [{ event: "data/process.large" }] },
  async ({ event, step }) => {
    const chunks = chunkArray(event.data.items, 10);

    // Process chunks in parallel
    const results = await Promise.all(
      chunks.map((chunk, index) =>
        step.run(`process-chunk-${index}`, () => processChunk(chunk)),
      ),
    );

    // Combine results
    await step.run("combine-results", () => {
      return aggregateResults(results);
    });
  },
);