Inngest Durable Functions

// ❌ BAD: Non-deterministic logic outside steps
async ({ event, step }) => {
  const timestamp = Date.now(); // This runs multiple times!

  const result = await step.run("process-data", () => {
    return processData(event.data);
  });
};

// ✅ GOOD: All non-deterministic logic in steps
async ({ event, step }) => {
  const result = await step.run("process-with-timestamp", () => {
    const timestamp = Date.now(); // Only runs once
    return processData(event.data, timestamp);
  });
};

const processOrder = inngest.createFunction(
  {
    id: "process-order", // Unique, never change this
    triggers: [{ event: "order/created" }],
    retries: 4, // Default: 4 retries per step
    concurrency: 10, // Max concurrent executions
  },
  async ({ event, step }) => {
    // Your durable workflow
  },
);

// Step IDs can be reused - Inngest handles counters automatically
const data = await step.run("fetch-data", () => fetchUserData());
const more = await step.run("fetch-data", () => fetchOrderData()); // Different execution

// Use descriptive IDs for clarity
await step.run("validate-payment", () => validatePayment(event.data.paymentId));
await step.run("charge-customer", () => chargeCustomer(event.data));
await step.run("send-confirmation", () => sendEmail(event.data.email));

// Single event trigger
inngest.createFunction(
  { id: "my-fn", triggers: [{ event: "user/signup" }] },
  async ({ event }) => {
    /* ... */
  },
);

// Event with conditional filter
inngest.createFunction(
  {
    id: "my-fn",
    triggers: [
      {
        event: "user/action",
        if: 'event.data.action == "purchase" && event.data.amount > 100',
      },
    ],
  },
  async ({ event }) => {
    /* ... */
  },
);

// Multiple triggers (up to 10)
inngest.createFunction(
  {
    id: "my-fn",
    triggers: [
      { event: "user/signup" },
      { event: "user/login", if: "event.data.firstLogin == true" },
      { cron: "0 9 * * *" }, // Daily at 9 AM
    ],
  },
  async ({ event }) => {
    /* ... */
  },
);

// Basic cron
inngest.createFunction(
  { id: "my-fn", triggers: [{ cron: "0 */6 * * *" }] }, // Every 6 hours
  async ({ step }) => {
    /* ... */
  },
);

// With timezone
inngest.createFunction(
  { id: "my-fn", triggers: [{ cron: "TZ=Europe/Paris 0 12 * * 5" }] }, // Fridays at noon Paris time
  async ({ step }) => {
    /* ... */
  },
);

// Combine with events
inngest.createFunction(
  {
    id: "my-fn",
    triggers: [
      { event: "manual/report.requested" },
      { cron: "0 0 * * 0" }, // Weekly on Sunday
    ],
  },
  async ({ event, step }) => {
    /* ... */
  },
);

// Invoke another function as a step
const result = await step.invoke("generate-report", {
  function: generateReportFunction,
  data: { userId: event.data.userId },
});

// Use returned data
await step.run("process-report", () => {
  return processReport(result);
});

// Prevent duplicate events with custom ID
await inngest.send({
  id: `checkout-completed-${cartId}`, // 24-hour deduplication
  name: "cart/checkout.completed",
  data: { cartId, email: "user@example.com" },
});

const sendEmail = inngest.createFunction(
  {
    id: "send-checkout-email",
    triggers: [{ event: "cart/checkout.completed" }],
    // Only run once per cartId per 24 hours
    idempotency: "event.data.cartId",
  },
  async ({ event, step }) => {
    // This function won't run twice for same cartId
  },
);

// Complex idempotency keys
const processUserAction = inngest.createFunction(
  {
    id: "process-user-action",
    triggers: [{ event: "user/action.performed" }],
    // Unique per user + organization combination
    idempotency: 'event.data.userId + "-" + event.data.organizationId',
  },
  async ({ event, step }) => {
    /* ... */
  },
);

const processOrder = inngest.createFunction(
  {
    id: "process-order",
    triggers: [{ event: "order/created" }],
    cancelOn: [
      {
        event: "order/cancelled",
        if: "event.data.orderId == async.data.orderId",
      },
    ],
  },
  async ({ event, step }) => {
    await step.sleepUntil("wait-for-payment", event.data.paymentDue);
    // Will be cancelled if order/cancelled event received
    await step.run("charge-payment", () => processPayment(event.data));
  },
);

const processWithTimeout = inngest.createFunction(
  {
    id: "process-with-timeout",
    triggers: [{ event: "long/process.requested" }],
    timeouts: {
      start: "5m", // Cancel if not started within 5 minutes
      finish: "30m", // Cancel if not finished within 30 minutes
    },
  },
  async ({ event, step }) => {
    /* ... */
  },
);

// Listen for cancellation events
const cleanupCancelled = inngest.createFunction(
  {
    id: "cleanup-cancelled-process",
    triggers: [{ event: "inngest/function.cancelled" }],
  },
  async ({ event, step }) => {
    if (event.data.function_id === "process-order") {
      await step.run("cleanup-resources", () => {
        return cleanupOrderResources(event.data.run_id);
      });
    }
  },
);

const reliableFunction = inngest.createFunction(
  {
    id: "reliable-function",
    triggers: [{ event: "critical/task" }],
    retries: 10, // Up to 10 retries per step
  },
  async ({ event, step, attempt }) => {
    // `attempt` is the function-level attempt counter (0-indexed)
    // It tracks retries for the currently executing step, not the overall function
    if (attempt > 5) {
      // Different logic for later attempts of the current step
    }
  },
);

import { NonRetriableError } from "inngest";

const processUser = inngest.createFunction(
  { id: "process-user", triggers: [{ event: "user/process.requested" }] },
  async ({ event, step }) => {
    const user = await step.run("fetch-user", async () => {
      const user = await db.users.findOne(event.data.userId);

      if (!user) {
        // Don't retry - user doesn't exist
        throw new NonRetriableError("User not found, stopping execution");
      }

      return user;
    });

    // Continue processing...
  },
);

import { RetryAfterError } from "inngest";

const respectRateLimit = inngest.createFunction(
  { id: "api-call", triggers: [{ event: "api/call.requested" }] },
  async ({ event, step }) => {
    await step.run("call-api", async () => {
      const response = await externalAPI.call(event.data);

      if (response.status === 429) {
        // Retry after specific time from API
        const retryAfter = response.headers["retry-after"];
        throw new RetryAfterError("Rate limited", `${retryAfter}s`);
      }

      return response.data;
    });
  },
);

import winston from "winston";

// Configure logger
const logger = winston.createLogger({
  level: "info",
  format: winston.format.json(),
  transports: [new winston.transports.Console()],
});

const inngest = new Inngest({
  id: "my-app",
  logger, // Pass logger to client
});

// Or use the built-in ConsoleLogger for simple log level control
import { ConsoleLogger, Inngest } from "inngest";

const inngest = new Inngest({
  id: "my-app",
  logger: new ConsoleLogger({ level: "debug" }), // "debug" | "info" | "warn" | "error"
});

const processData = inngest.createFunction(
  { id: "process-data", triggers: [{ event: "data/process.requested" }] },
  async ({ event, step, logger }) => {
    // ✅ GOOD: Log inside steps to avoid duplicates
    const result = await step.run("fetch-data", async () => {
      logger.info("Fetching data for user", { userId: event.data.userId });
      return await fetchUserData(event.data.userId);
    });

    // ❌ AVOID: Logging outside steps can duplicate
    // logger.info("Processing complete"); // This could run multiple times!

    await step.run("log-completion", async () => {
      logger.info("Processing complete", { resultCount: result.length });
    });
  },
);

// Checkpointing is enabled by default in v4
// Configure maxRuntime for serverless platforms (set to 60-80% of platform timeout)
const realTimeFunction = inngest.createFunction(
  {
    id: "real-time-function",
    triggers: [{ event: "realtime/process" }],
    checkpointing: {
      maxRuntime: "50s", // For serverless with 60s timeout
    },
  },
  async ({ event, step }) => {
    // Steps execute immediately with periodic checkpointing
    const result1 = await step.run("step-1", () => process1(event.data));
    const result2 = await step.run("step-2", () => process2(result1));
    return { result2 };
  },
);

// Disable checkpointing if needed
const legacyFunction = inngest.createFunction(
  {
    id: "legacy-function",
    triggers: [{ event: "legacy/process" }],
    checkpointing: false,
  },
  async ({ event, step }) => {
    /* ... */
  },
);