使用CDK部署Lambda时出现模块找不到错误的求助

问题描述 #

使用AWS CDK开发无服务器应用，TypeScript文件编译后部署Lambda函数，调用时出现「模块未找到」错误，提示无法找到@aws-sdk/client-dynamodb模块。

部署步骤 #

• tsc：编译TS文件
• cdk synth：生成CloudFormation模板
• cdk deploy：部署堆栈

TypeScript配置 #

{
  "compilerOptions": {
    "target": "ES2018",
    "module": "commonjs",
    "lib": [
      "es2018"
    ],
    "noEmit": false,
    "declaration": false,
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "noImplicitThis": true,
    "alwaysStrict": true,
    "noUnusedLocals": false,
    "noUnusedParameters": false,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": false,
    "inlineSourceMap": true,
    "inlineSources": true,
    "experimentalDecorators": true,
    "strictPropertyInitialization": false,
    "typeRoots": [
      "./node_modules/@types"
    ]
  },
  "exclude": [
    "node_modules",
    "cdk.out"
  ]
}

Lambda函数代码 #

import { APIGatewayProxyEventV2, APIGatewayProxyResultV2 } from 'aws-lambda';
import { DynamoDBClient, GetItemCommand, GetItemCommandInput } from "@aws-sdk/client-dynamodb";
import { marshall, unmarshall } from "@aws-sdk/util-dynamodb";

export async function handler(event: APIGatewayProxyEventV2): Promise<APIGatewayProxyResultV2> {
  console.log('event', event);

  let userLat = event.pathParameters?.lat;
  let userLng = event.pathParameters?.lng;
  let tableName = process.env.TABLE_NAME;
  let results;

  const dbClient: DynamoDBClient = new DynamoDBClient({ region: "ap-south-1" });
  let params: GetItemCommandInput;

  if (tableName) {
    params = {
      TableName: tableName,
      Key: marshall({
        "lat": userLat,
        "lng": userLng
      }),
    };
  }

  const run = async function () {
    try {
      const resp = await dbClient.send(new GetItemCommand(params));
      results = unmarshall(resp.Item || {});
    } catch(err) {
      results = err;
    }
  };

  run();

  return {
    body: JSON.stringify(results),
    statusCode: 200
  };
}

环境信息 #

• Node: v14.20.0
• NPM: 6.14.17
• CDK: 2.40.0 (build 56ba2ab)
• TypeScript: Version 4.8.2

错误信息 #

{"errorType": "Runtime.ImportModuleError","errorMessage": "Error: Cannot find module '@aws-sdk/client-dynamodb'\nRequire stack:\n- /var/task/fetchpartner.js\n- /var/runtime/UserFunction.js\n- /var/runtime/Runtime.js\n- /var/runtime/index.js","trace": ["Runtime.ImportModuleError: Error: Cannot find module '@aws-sdk/client-dynamodb'","Require stack:","- /var/task/fetchpartner.js","- /var/runtime/UserFunction.js","- /var/runtime/Runtime.js","- /var/runtime/index.js"," at _loadUserApp (/var/runtime/UserFunction.js:221:13)"," at Object.module.exports.load (/var/runtime/UserFunction.js:279:17)"," at Object. (/var/runtime/index.js:43:34)"," at Module._compile (internal/modules/cjs/loader.js:1085:14)"," at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)"," at Module.load (internal/modules/cjs/loader.js:950:32)"," at Function.Module._load (internal/modules/cjs/loader.js:790:12)"," at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:75:12)"," at internal/main/run_main_module.js:17:47"]}

解决方案 #

1. 检查依赖安装类型 #

确保@aws-sdk/client-dynamodb和@aws-sdk/util-dynamodb是生产依赖，而非开发依赖。执行以下命令重新安装：

npm install @aws-sdk/client-dynamodb @aws-sdk/util-dynamodb --save

如果之前误安装为开发依赖（--save-dev），需要先卸载再重新安装：

npm uninstall @aws-sdk/client-dynamodb @aws-sdk/util-dynamodb --save-dev
npm install @aws-sdk/client-dynamodb @aws-sdk/util-dynamodb --save

2. 配置CDK正确打包Lambda代码 #

推荐使用CDK的NodejsFunction构造，它会自动通过esbuild打包代码并包含所需依赖，无需手动处理node_modules。示例堆栈代码：

import { NodejsFunction } from 'aws-cdk-lib/aws-lambda-nodejs';
import { Stack, StackProps } from 'aws-cdk-lib';
import { Construct } from 'constructs';

export class YourStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    new NodejsFunction(this, 'FetchPartnerFunction', {
      entry: './path/to/your/lambda.ts', // 指向你的TS文件路径
      handler: 'handler',
      runtime: lambda.Runtime.NODEJS_14_X,
      environment: {
        TABLE_NAME: 'your-table-name'
      }
    });
  }
}

如果使用普通Function构造，需要手动将node_modules和编译后的JS文件一起打包，或者使用webpack/esbuild将代码打包成单个文件，避免依赖缺失。

3. 修正Lambda异步逻辑问题 #

代码中run()是异步函数却未使用await，会导致函数提前返回results（此时为undefined）。修改为：

await run();

4. 验证编译后的文件结构 #

执行tsc后，检查编译后的JS文件是否在CDK指定的代码目录下，且该目录包含正确的依赖（如果手动打包的话）。确保CDK的Function配置中的code属性正确指向编译后的代码目录。

内容的提问来源于stack exchange，提问作者Karthik Rajan