AWS Lambda运行报错index.handler未定义或未导出，该如何解决？

错误详情 #

该错误为Lambda Node.js运行时典型的Handler入口找不到错误，完整报错如下：

{
  "errorType": "Runtime.HandlerNotFound",
  "errorMessage": "index.handler is undefined or not exported",
  "trace": [
    "Runtime.HandlerNotFound: index.handler is undefined or not exported",
    "    at Object.module.exports.load (/var/runtime/UserFunction.js:144:11)",
    "    at Object.<anonymous> (/var/runtime/index.js:43:30)",
    "    at Module._compile (internal/modules/cjs/loader.js:999:30)",
    "    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)",
    "    at Module.load (internal/modules/cjs/loader.js:863:32)",
    "    at Function.Module._load (internal/modules/cjs/loader.js:708:14)",
    "    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)",
    "    at internal/main/run_main_module.js:17:47"
  ]
}

对应的函数运行日志：

START RequestId: fa81b4c8-23f6-4f15-899b-dfc680ae9c57 Version: $LATEST
2021-10-29T08:47:21.477Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.HandlerNotFound","errorMessage":"index.handler is undefined or not exported","stack":["Runtime.HandlerNotFound: index.handler is undefined or not exported","    at Object.module.exports.load (/var/runtime/UserFunction.js:144:11)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}
2021-10-29T08:47:22.789Z    undefined   ERROR   Uncaught Exception  {"errorType":"Runtime.HandlerNotFound","errorMessage":"index.handler is undefined or not exported","stack":["Runtime.HandlerNotFound: index.handler is undefined or not exported","    at Object.module.exports.load (/var/runtime/UserFunction.js:144:11)","    at Object.<anonymous> (/var/runtime/index.js:43:30)","    at Module._compile (internal/modules/cjs/loader.js:999:30)","    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)","    at Module.load (internal/modules/cjs/loader.js:863:32)","    at Function.Module._load (internal/modules/cjs/loader.js:708:14)","    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)","    at internal/main/run_main_module.js:17:47"]}
END RequestId: fa81b4c8-23f6-4f15-899b-dfc680ae9c57
REPORT RequestId: fa81b4c8-23f6-4f15-899b-dfc680ae9c57  Duration: 1463.33 ms    Billed Duration: 1464 ms    Memory Size: 128 MB Max Memory Used: 11 MB  
Unknown application error occurred
Runtime.HandlerNotFound

排查&解决步骤 #

按以下顺序逐一核对即可解决问题：

• 检查index.js的导出规则是否符合运行时要求
  默认Lambda Node.js运行时使用CommonJS模块规范，必须按以下方式导出handler函数：

  // 正确写法1
  exports.handler = async (event, context) => {
    // 业务逻辑代码
    return { statusCode: 200, body: '执行完成' }
  }
  
  // 正确写法2
  const handler = async (event, context) => { /* 逻辑代码 */ }
  module.exports.handler = handler
  

  注：如果使用ES模块规范，需要在同级目录的package.json中添加"type": "module"配置，同时使用export const handler = async () => {}的写法导出
• 核对Lambda控制台的handler配置
  进入Lambda函数配置页的「运行时设置」模块，确认handler参数配置为index.handler。如果你的入口文件名不是index.js或者导出的函数名不是handler，需要对应修改配置，例如入口文件为app.js、导出函数名为entry，则配置应为app.entry。
• 检查部署包的文件结构
  如果是手动打包zip上传的部署包，解压后确认index.js位于压缩包根目录，而非嵌套在子文件夹中。常见错误是打包时将整个代码文件夹打包，导致解压后index.js位于src/等子目录下，Lambda在根目录找不到对应文件就会触发该错误。
• 确认运行时版本匹配
  如果你使用了ES模块语法，需要确认Lambda运行时版本为Node.js 14.x及以上，低版本运行时不支持ES模块规范。

内容的提问来源于stack exchange，提问作者user630702