使用k6+Webpack测试AWS Cognito授权接口时遇URL未定义错误

问题背景 #

对需AWS Cognito授权的应用接口做性能测试，选用k6+Webpack组合。调用await client.initiateAuth(params)（client为CognitoIdentityProvider实例）时抛出ReferenceError: URL is not defined异常。调试发现：不使用Webpack时，await client.config.endpoint()能返回正确Cognito地址；使用Webpack则触发相同错误。

相关代码及运行日志如下：

index.js #

import http from 'k6/http';
import { Rate, Trend } from 'k6/metrics';
import { check } from 'k6';
import { getToken } from "./cognito-service";

var errors = new Rate("errors");
var trends = new Trend("trends");

export const options = {
    vus: 1,
    duration: '10s',
};
const token = getToken();

const params = {
  headers: {
    'Authorization': 'Bearer ' + token,
  },
};

export default function () {
  const res = http.get('https://myurl.com/api/need/to/test', params);
  check(res, { 'status was 200': (r) => r.status == 200 });
  errors.add(res.error_code);
  trends.add(res.timings.sending + res.timings.receiving);
}

webpack.config.js #

const path = require('path');

module.exports = {
  mode: 'production',
  entry: {
    login: './index.js',
  },
  output: {
    path: path.resolve(__dirname, 'build'),
    libraryTarget: 'commonjs',
    filename: '[name].bundle.js',
  },
  module: {
    rules: [
      { test: /\.js$/, use: 'babel-loader' }
    ],
  },
  target: 'web',
  externals: /k6(\/.*)?/,
};

cognito-service.js #

import { CognitoIdentityProvider } from "@aws-sdk/client-cognito-identity-provider";

export const getToken = async () => {
    const clientId = "XXXXXXXXXX";
    const params = {
        AuthFlow: "USER_PASSWORD_AUTH",
        ClientId: clientId,
        AuthParameters: { "USERNAME": "xxxxxx@gmail.com", "PASSWORD": "Test123$" }
    };
    const client = new CognitoIdentityProvider({ region: "eu-central-1" });
    try {
        console.log(client.config);
        const response = await client.initiateAuth(params);
        console.log(`Response is -> ${response}`)
        return response;
    } catch(error) {
        console.log(`Err is -> ${error}`);
    }
}

运行日志 #

> k6 run build/login.bundle.js


          /\      |‾‾| /‾‾/   /‾‾/
     /\  /  \     |  |/  /   /  /
    /  \/    \    |     (   /   ‾‾\
   /          \   |  |\  \ |  (‾)  |
  / __________ \  |__| \__\ \_____/ .io

INFO[0000] {"apiVersion":"2016-04-18","disableHostPrefix":false,"logger":{},"serviceId":"Cognito Identity Provider","runtime":"browser","requestHandler":{"configProvider":{}},"tls":true,"isCustomEndpoint":false,"systemClockOffset":0,"signingEscapePath":true}  source=console
INFO[0000] Err is -> ReferenceError: URL is not defined  source=console
  execution: local
     script: build/login.bundle.js
     output: -

  scenarios: (100.00%) 1 scenario, 1 max VUs, 40s max duration (incl. graceful stop):
           * default: 1 looping VUs for 10s (gracefulStop: 30s)

INFO[0000] {"apiVersion":"2016-04-18","disableHostPrefix":false,"logger":{},"serviceId":"Cognito Identity Provider","runtime":"browser","requestHandler":{"configProvider":{}},"tls":true,"isCustomEndpoint":false,"systemClockOffset":0,"signingEscapePath":true}  source=console
INFO[0000] Err is -> ReferenceError: URL is not defined  source=console
INFO[0000] {"apiVersion":"2016-04-18","disableHostPrefix":false,"logger":{},"serviceId":"Cognito Identity Provider","runtime":"browser","requestHandler":{"configProvider":{}},"tls":true,"isCustomEndpoint":false,"systemClockOffset":0,"signingEscapePath":true}  source=console
INFO[0000] Err is -> ReferenceError: URL is not defined  source=console

原因分析 #

1. Webpack目标环境不匹配：Webpack配置中target: 'web'会让AWS SDK判定运行环境为浏览器，但k6的执行环境是基于Go的V8引擎，并非标准浏览器环境，缺少浏览器全局对象URL。
2. 异步函数调用时机错误：getToken是异步函数，在k6全局作用域直接调用const token = getToken()会导致未正确获取到token，且k6不支持在全局作用域执行异步操作。

解决方案 #

1. 修改Webpack配置，适配k6环境 #

将Webpack的target改为'node'，让AWS SDK使用Node.js环境的API实现，同时添加Node.js核心模块的polyfill：

首先安装依赖：

npm install node-polyfill-webpack-plugin --save-dev

修改后的webpack.config.js：

const path = require('path');
const NodePolyfillPlugin = require('node-polyfill-webpack-plugin');

module.exports = {
  mode: 'production',
  entry: {
    login: './index.js',
  },
  output: {
    path: path.resolve(__dirname, 'build'),
    libraryTarget: 'commonjs',
    filename: '[name].bundle.js',
  },
  module: {
    rules: [
      { test: /\.js$/, use: 'babel-loader' }
    ],
  },
  target: 'node',
  externals: /k6(\/.*)?/,
  plugins: [
    new NodePolyfillPlugin()
  ]
};

2. 修正k6脚本中的异步调用逻辑 #

k6中异步操作需放在setup函数（初始化阶段执行，支持异步）或default函数（需标记为async）中。这里推荐用setup函数预获取token：

修改后的index.js：

import http from 'k6/http';
import { Rate, Trend } from 'k6/metrics';
import { check } from 'k6';
import { getToken } from "./cognito-service";

var errors = new Rate("errors");
var trends = new Trend("trends");

export const options = {
    vus: 1,
    duration: '10s',
};

// 用setup函数异步获取token，所有VU共享
export async function setup() {
  const tokenData = await getToken();
  return { token: tokenData.AuthenticationResult.IdToken };
}

export default function (data) {
  const params = {
    headers: {
      'Authorization': 'Bearer ' + data.token,
    },
  };
  const res = http.get('https://myurl.com/api/need/to/test', params);
  check(res, { 'status was 200': (r) => r.status == 200 });
  errors.add(res.error_code || 0);
  trends.add(res.timings.sending + res.timings.receiving);
}

3. 完善cognito-service.js的返回值与配置 #

指定AWS SDK运行时为Node.js，确保返回有效token数据：

import { CognitoIdentityProvider } from "@aws-sdk/client-cognito-identity-provider";

export const getToken = async () => {
    const clientId = "XXXXXXXXXX";
    const params = {
        AuthFlow: "USER_PASSWORD_AUTH",
        ClientId: clientId,
        AuthParameters: { "USERNAME": "xxxxxx@gmail.com", "PASSWORD": "Test123$" }
    };
    const client = new CognitoIdentityProvider({ 
        region: "eu-central-1",
        runtime: 'node'
    });
    try {
        const response = await client.initiateAuth(params);
        return response;
    } catch(error) {
        console.error(`获取token失败: ${error}`);
        throw error;
    }
}

验证 #

重新打包并运行k6脚本：

npm run build
k6 run build/login.bundle.js

此时应能正常获取Cognito token，不再抛出URL is not defined异常，接口请求可携带有效授权头。

内容的提问来源于stack exchange，提问作者Tomash Gombosh