Lambda调用DynamoDB.update后无日志静默失败，请求协助排查

我使用Lambda函数处理DynamoDB插入流，执行dynamoDB.update调用后，Lambda异常终止且无后续日志输出。移除更新逻辑后日志恢复正常，代码如下：

/* Amplify Params - DO NOT EDIT
  API_SCHOLARGRAPH_EMPLOYEEINFOTABLE_ARN
  API_SCHOLARGRAPH_EMPLOYEEINFOTABLE_NAME
  ENV
  REGION
Amplify Params - DO NOT EDIT */


const AWS = require('aws-sdk');

const awsConfig = {
  region: process.env.REGION,
  endpoint:
    process.env.DYNAMODB_ENDPOINT ||
    `https://dynamodb.${process.env.REGION}.amazonaws.com`
};

const dynamoDB = new AWS.DynamoDB.DocumentClient(awsConfig);

async function handleNewEmployeeInfo(dynamoId, employeeId) {
  console.log(
    `[handleNewEmployeeInfo] begin. dynamoId(${dynamoId}) employeeId(${employeeId})`
  );

  try {
    const employeeName = "TestString";

    // this log is working
    console.log(
      'try to update table:',
      process.env.API_SCHOLARGRAPH_EMPLOYEEINFOTABLE_NAME,
      dynamoId,
      employeeName
    );

    // something wrong with the update
    await dynamoDB
      .update({
        TableName: process.env.API_SCHOLARGRAPH_EMPLOYEEINFOTABLE_NAME,
        Key: {
          id: dynamoId
        },
        UpdateExpression: `set employeeName = :employeeName`,
        ExpressionAttributeValues: {
          ':employeeName': employeeName
        }
      })
      .promise()
      .then((data) => console.log(data.Attributes))
      .catch(console.error);
  } catch (error) {
    // NOT working
    console.log('[ERROR]:', error);
  }

  // NOT working
  console.log('[FINISH] call end');
}

async function handleEventRecord(record) {
  console.log(record.eventID);
  console.log(record.eventName);

  try {
    // after EmployeeInfo is created by the admin
    if (record.eventName === 'INSERT') {
      const arn = record.eventSourceARN;
      console.log(`[INSERT][${arn}]: ${JSON.stringify(record)}`);
      if (arn.includes(':table/EmployeeInfo')) {
        const dynamoId = record.dynamodb.NewImage.id['S'];
        const employeeId = record.dynamodb.NewImage.employeeId['S'];
        await handleNewEmployeeInfo(dynamoId, employeeId);
      }
    }
  } catch (error) {
    console.log('[ERROR]:', error);
  }
}

/**
 * @type {import('@types/aws-lambda').APIGatewayProxyHandler}
 */
exports.handler = async (event) => {
  console.log(`EVENT: ${JSON.stringify(event)}`);
  event.Records.forEach(async (record) => {
    await handleEventRecord(record);
  });

  return Promise.resolve('Successfully processed DynamoDB record');
};

问题根源与修复方案 #

1. 异步错误捕获逻辑冲突 #

handleNewEmployeeInfo中混合使用await和.then()/.catch()，导致try/catch无法捕获DynamoDB操作的异常。.catch()已经内部捕获异常并打印，但未重新抛出，外层try/catch无法感知；若.catch()执行出错（比如日志输出异常），会直接导致Lambda进程崩溃。

修复代码：

async function handleNewEmployeeInfo(dynamoId, employeeId) {
  console.log(
    `[handleNewEmployeeInfo] begin. dynamoId(${dynamoId}) employeeId(${employeeId})`
  );

  try {
    const employeeName = "TestString";
    console.log(
      'try to update table:',
      process.env.API_SCHOLARGRAPH_EMPLOYEEINFOTABLE_NAME,
      dynamoId,
      employeeName
    );

    // 统一用try/catch处理，去掉.then/.catch
    const data = await dynamoDB.update({
      TableName: process.env.API_SCHOLARGRAPH_EMPLOYEEINFOTABLE_NAME,
      Key: { id: dynamoId },
      UpdateExpression: `set employeeName = :employeeName`,
      ExpressionAttributeValues: { ':employeeName': employeeName }
    }).promise();
    
    console.log(data.Attributes);
  } catch (error) {
    console.log('[ERROR]:', error);
  }

  console.log('[FINISH] call end');
}

2. Lambda Handler未等待异步任务完成 #

exports.handler中使用forEach遍历异步函数，forEach不会等待异步操作执行完毕，Lambda会提前返回并终止进程，导致后续日志和代码逻辑无法执行。

修复代码：

exports.handler = async (event) => {
  console.log(`EVENT: ${JSON.stringify(event)}`);
  // 用Promise.all等待所有异步处理完成
  await Promise.all(event.Records.map(async (record) => {
    await handleEventRecord(record);
  }));

  return 'Successfully processed DynamoDB record';
};

3. 额外检查项 #

• IAM权限验证：确认Lambda执行角色拥有目标DynamoDB表的dynamodb:UpdateItem权限
• 数据类型匹配：检查dynamoId的类型是否与表中id字段类型一致（比如表中是字符串类型，需确保获取的S值格式正确）
• 记录存在性：如果更新的记录不存在，默认会抛出ConditionalCheckFailedException，需根据业务需求添加ConditionExpression或处理该异常

内容的提问来源于stack exchange，提问作者Ning