在Vercel部署NextJS时出现ENOENT创建目录错误求助

本地localhost运行正常的代码如下：

import fs from 'fs'
import path from 'path'

export default function createUserDir (tokenSignature: string) { 
    const pathToMakeDir = path.join(process.cwd(), 'notes', tokenSignature);
    fs.mkdirSync(pathToMakeDir, { recursive: true });    
}

部署到Vercel（Next.js 13.0.3，Node 16.x）后出现如下错误：

2022-11-15T19:32:34.119Z    145c46ab-416c-4f5c-b881-80b9c623a5ac    ERROR   Error: ENOENT: no such file or directory, mkdir '/var/task/notes/jFlqLkrmIPOEnaiExiUN3ohlmJlH_GN2OD36fiQ9a2A'
    at Object.mkdirSync (node:fs:1349:3)
    at createUserDir (/var/task/.next/server/chunks/133.js:252:45)
    at getServerSideProps (/var/task/.next/server/pages/index.js:93:76)
    at Object.renderToHTML (/var/task/node_modules/next/dist/server/render.js:506:26)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async doRender (/var/task/node_modules/next/dist/server/base-server.js:701:34)
    at async cacheEntry.responseCache.get.isManualRevalidate.isManualRevalidate (/var/task/node_modules/next/dist/server/base-server.js:806:28)
    at async /var/task/node_modules/next/dist/server/response-cache/index.js:80:36 {
  errno: -2,
  syscall: 'mkdir',
  path: '/var/task/notes/jFlqLkrmIPOEnaiExiUN3ohlmJlH_GN2OD36fiQ9a2A',
  page: '/'
}
RequestId: 145c46ab-416c-4f5c-b881-80b9c623a5ac Error: Runtime exited with error: exit status 1
Runtime.ExitError

解决方案 #

• 核心原因：Vercel的/var/task目录是只读的，无法写入文件或创建目录；本地环境中process.cwd()指向有写入权限的项目目录，因此本地运行正常。
• 临时存储修改：改用Vercel允许写入的临时目录/tmp，调整代码路径：

  import fs from 'fs'
  import path from 'path'
  
  export default function createUserDir (tokenSignature: string) { 
      const pathToMakeDir = path.join('/tmp', 'notes', tokenSignature);
      fs.mkdirSync(pathToMakeDir, { recursive: true });    
  }
  

  注意：/tmp目录的内容会在函数执行结束后被自动清理，仅适合临时存储场景。
• 持久化存储方案：如果需要长期保存文件，应使用Vercel官方Blob Storage或第三方云存储服务（如AWS S3），Vercel的Serverless函数环境不提供持久化本地存储能力。

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