Serverless+Lambda部署Express代码，S3图片URL显示损坏问题求助

我是AWS和Serverless框架新手。相同的Express.js代码，在Elastic Beanstalk单独部署后端时，能正常上传图片到AWS S3，生成的URL可以在浏览器正常显示图片；但用Serverless框架通过Lambda函数部署后，虽然能把图片上传到同一个S3存储桶，生成的图片URL却只显示损坏图标（图片无法打开的默认占位图）。两种场景下，上传后获取的图片URL都会和其他文本数据一起存储到Amazon RDS MySQL数据库里。我已经确认Access Key和Secret Key是正确的，相关配置代码如下：

serverless.yaml 文件 #

service: serverlessbackend
frameworkVersion: "3"

provider:
  name: aws
  runtime: nodejs18.x
  region: ap-south-1
  timeout: 10
  environment:
    DB_HOST: "something.rds.amazonaws.com"
    DB_USER: "user"
    DB_PASSWORD: "something"
    DB_NAME: "something"
    AWS_ACCESSKEY: "something"
    AWS_SECRETKEY: "something"
    MY_AWS_REGION: "ap-south-1"


functions:
  myLambdaFunction:
    handler: index.handler
    events:
      - http: ANY /
      - http: "ANY {proxy+}"

plugins:
  - serverless-offline

index.js 文件 #

const serverless = require("serverless-http");
const express = require("express");
const app = express();
const mysql = require("mysql2");
app.use(express.json());
let pool = require("./db/index");

let categoryRoutes = require("./routes/categoryRoutes");


app.use("/category", categoryRoutes);


module.exports.handler = serverless(app);

categoryRoutes.js 文件 #

const express = require("express");
const { pool } = require("../db");
const { deleteFromAws, uploadToAws } = require("../utils/aws");
const multer = require("multer");
const { uniqueString } = require("../utils/unique");

const router = express.Router();


const storage = multer.memoryStorage();

const upload = multer({
  storage: storage,
});


router.post("/", upload.single("image"), async (req, res) => {

  console.log(req.file);
  if (!req.file) {
    return res.status(400).json({ error: "No file uploaded" });
  }

  try {
  
    let result = await uploadToAws(req.file);
  
    let { Location: imgUrl, Key } = result;

    console.log(result);
  

    if (imgUrl && Key) {
      const query = "INSERT INTO temp SET ?";

      const data = {
        category: req.body.category,
        category_id: uniqueString(),
        image_path: imgUrl,
        image_name: Key,
      };
      // The "?" in the query is a placeholder for the data object

      pool.query(query, data, (err, result) => {
        if (err) {
          console.log(err);
          return res.status(400).json({ message: err.message });
        }
        // console.log(result);
        return res.status(200).json({ message: "File uploaded successfully" });
      });
    } else {
      throw new Error("something wrong");
    }
  } catch (err) {
    console.log(err.message);
    res.send(err.message);
  }
});

uploadToAws 工具文件 #

const AWS = require("aws-sdk");
const { generateUniqueImageName } = require("./unique");

// Configure AWS credentials
AWS.config.update({
  accessKeyId: process.env.AWS_ACCESSKEY,
  secretAccessKey: process.env.AWS_SECRETKEY,
  region: process.env.MY_AWS_REGION, // e.g., 'us-east-1'
});

// Create a new instance of the S3 service

const uploadToAws = async (file) => {
  // console.log(file);
  
  const s3 = new AWS.S3();

  const params = {
    Bucket: "something",
    Key: `uploads/IMG-${generateUniqueImageName(file.originalname)}`, // The file name to be used in the S3 bucket
    ContentType: file.mimetype,
    Body: file.buffer, // The file content as a buffer
  };

  return await s3.upload(params).promise();
};

Serverless框架部署后的图片URL显示效果 #

Elastic Beanstalk部署后的图片URL显示效果 #

1. 检查文件内容完整性

   • 在Lambda环境中打印req.file.buffer的大小，对比Elastic Beanstalk环境中的值，确认文件是否完整传递。Lambda默认请求payload上限为6MB，若图片超过该大小会被截断，导致S3中文件损坏。

2. 验证S3对象实际内容

   • 直接在AWS控制台下载Lambda上传的图片，查看本地是否能打开。如果本地也无法打开，说明上传过程中文件内容已损坏。

3. 检查Lambda执行角色权限

   • 虽然使用了硬编码密钥，但Lambda环境更推荐用IAM角色。确认Lambda执行角色是否具备s3:PutObject权限，且无额外限制导致上传异常。

4. 核实ContentType设置

   • 确认Lambda环境中file.mimetype是否正确获取，比如是否被错误识别为application/octet-stream。可手动根据文件后缀指定ContentType，或在S3控制台查看已上传文件的ContentType是否匹配图片类型。

5. 查看Lambda日志

   • 检查CloudWatch中的Lambda日志，确认uploadToAws函数是否报错，或result返回的Location、Key等信息是否异常。

内容的提问来源于stack exchange，提问作者Ankit Devbanshi