inngest-durable-functions

Inngest 持久化函数

掌握 Inngest 的持久化执行模型，构建容错的长时间运行工作流。本技能涵盖从触发器到错误处理的完整生命周期。

这些技能专注于 TypeScript。 如需 Python 或 Go 相关内容，请参阅 Inngest 文档以获取特定语言的指导。核心概念适用于所有语言。

需要了解的核心概念

持久化执行模型

• 每个步骤都应封装副作用和非确定性代码
• 记忆化可防止重新执行已完成的步骤
• 状态持久化可在基础设施故障后保留状态
• 自动重试，并可配置重试次数

步骤执行流程

// ❌ 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);
  });
};

函数限制

每个 Inngest 函数都有以下硬性限制：

• 每次函数运行最多 1,000 个步骤
• 每个步骤返回的数据最多 4MB
• 函数运行状态总量最多 32MB，包括事件数据、步骤输出和函数输出
• 每个步骤都会产生单独的 HTTP 请求（约 50-100ms 开销）

如果达到这些限制，请将函数拆分成更小的函数，并通过 step.invoke() 或 step.sendEvent() 连接。

何时使用步骤

始终使用 step.run() 封装：

• API 调用和网络请求
• 数据库读写
• 文件 I/O 操作
• 任何非确定性操作
• 任何希望在失败时独立重试的操作

绝不要使用 step.run() 封装：

• 纯计算和数据转换
• 简单的验证逻辑
• 没有副作用的确定性操作
• 日志记录（请在步骤外使用）

创建函数

基本函数结构

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
  }
);

步骤 ID 和记忆化

// 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));

触发器和事件

事件触发器

在 createFunction 第一个参数中的 triggers 数组里定义触发器：

// 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 }) => { /* ... */ }
);

Cron 触发器

// 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 }) => { /* ... */ }
);

函数调用

// 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);
});

幂等性策略

事件级幂等性（生产者端）

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

函数级幂等性（消费者端）

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 }) => {
    /* ... */
  }
);

取消模式

基于事件的取消

在表达式中，event = 原始触发事件，async = 正在匹配的新事件。完整详情请参阅表达式语法参考。

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));
  }
);

超时取消

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 }) => {
    /* ... */
  }
);

处理取消清理

// 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);
      });
    }
  }
);

错误处理和重试

默认重试行为

• 每个步骤总共 5 次尝试（1 次初始尝试 + 4 次重试）
• 带抖动的指数退避
• 每个步骤的重试计数器相互独立

自定义重试配置

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
    }
  }
);

不可重试的错误

对于重试后也不会成功的代码，阻止其重试。

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...
  }
);

自定义重试时机

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;
    });
  }
);

日志记录最佳实践

正确配置日志记录

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"
});

⚠️ v4 破坏性变更： logLevel 选项已移除。请改用 logger 选项，并使用 ConsoleLogger 或自定义日志记录器。

函数日志记录模式

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 });
    });
  }
);

性能优化

检查点

v4 中默认启用检查点。它允许函数在执行期间定期持久化状态，减少步骤之间的延迟。

// 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 }) => { /* ... */ }
);

高级模式

条件步骤执行

const conditionalProcess = inngest.createFunction(
  { id: "conditional-process", triggers: [{ event: "process/conditional" }] },
  async ({ event, step }) => {
    const userData = await step.run("fetch-user", () => {
      return getUserData(event.data.userId);
    });

    // Conditional step execution
    if (userData.isPremium) {
      await step.run("premium-processing", () => {
        return processPremiumFeatures(userData);
      });
    }

    // Always runs
    await step.run("standard-processing", () => {
      return processStandardFeatures(userData);
    });
  }
);

错误恢复模式

const robustProcess = inngest.createFunction(
  { id: "robust-process", triggers: [{ event: "process/robust" }] },
  async ({ event, step }) => {
    let primaryResult;

    try {
      primaryResult = await step.run("primary-service", () => {
        return callPrimaryService(event.data);
      });
    } catch (error) {
      // Fallback to secondary service
      primaryResult = await step.run("fallback-service", () => {
        return callSecondaryService(event.data);
      });
    }

    return { result: primaryResult };
  }
);

应避免的常见错误

1. ❌ 在步骤外执行非确定性代码
2. ❌ 在步骤外调用数据库
3. ❌ 在步骤外记录日志（会导致重复）
4. ❌ 部署后更改步骤 ID
5. ❌ 未处理 NonRetriableError 情况
6. ❌ 忽略关键函数的幂等性

后续步骤

• 查看 inngest-steps，了解详细的步骤方法参考
• 查看 references/step-execution.md，了解详细的步骤模式
• 查看 references/error-handling.md，了解全面的错误处理策略
• 查看 references/observability.md，了解监控和追踪设置
• 查看 references/checkpointing.md，了解性能优化详情

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本技能涵盖 Inngest 的持久化函数模式。有关事件发送和 Webhook 处理，请参阅 inngest-events 技能。