How to Solve Vercel Server Less function Crushed 500 Error for Express Server.

#programming #react #javascript #serverless

Introduction

Working with serverless functions on platforms like Vercel can be a seamless experience, but occasionally, challenges may arise. Recently, I encountered a serverless function crash on Vercel, and I'm here to share how I resolved it.

The Problem

The issue manifested as a 500 Internal Server Error, and the logs pointed towards a missing module: Cannot find module 'express'. This error message was puzzling as express was part of the project dependencies. The Error code looks like this,

`Cannot find module 'express'
Require stack:

/var/task/index.js
/var/task/___now_launcher.js
/var/runtime/index.mjs Did you forget to add it to "dependencies" in package.json? INIT_REPORT Init Duration: 202.73 ms Phase: invoke Status: error Error Type: Runtime.ExitError Error: Runtime exited with error: exit status 1 Runtime.ExitError`

Troubleshooting Steps

Dependency Check First, I double-checked my package.json file to ensure that express was listed as a dependency. Surprisingly, everything seemed fine.

"dependencies": { "express": "^4.18.2" },

Vercel Configuration Next, I revisited the vercel.json file. The configuration for serverless functions is crucial here. Previous config was

{
  "version": 2,
  "builds": [
    {
      "src": "index.js",
      "use": "@now/node"
    }
  ],
  "routes": [
    {
      "src": "/(.*)",
      "dest": "index.js"
    }
  ]
}

The Solution

{
    "version": 2,
    "builds": [
        {
            "src": "index.js",
            "use": "@vercel/node"
        }
    ],
    "routes": [
        {
            "src": "/(.*)",
            "dest": "/",
            "methods": [
                "GET",
                "POST",
                "PUT",
                "PATCH",
                "DELETE",
                "OPTIONS"
            ]
        }
    ]
}