NodeJS API本地运行正常但部署至Heroku后仅根路由可访问，其余路由返回404问题求助

Hey there, let's figure out why only your / route works on Heroku while all others throw 404s—especially since everything runs smoothly locally. Here are the most likely culprits and how to fix them:

1. Missing or Misconfigured Procfile #

Heroku relies on a Procfile to know exactly how to start your app. If it's missing or set up wrong, your API might fail to load all routes properly.

• Check for a Procfile: It should live in your project root (no file extension) with this line:

  web: node app.js
  

• Verify your package.json scripts: Make sure you have a start script pointing to your entry file:

  "scripts": {
    "start": "node app.js",
    ...
  }
  

  If you skip the Procfile, Heroku uses the start script by default—so this needs to be accurate.

2. Incorrect Router Export in Route Files #

If your route files don't properly export an Express Router instance, Heroku won't recognize those endpoints. Double-check each route file (like students.js):

const express = require('express');
const router = express.Router();

// Example route
router.get('/', (req, res) => {
  res.send('Student route works!');
});

// Critical: Make sure this line exists!
module.exports = router;

Without module.exports = router;, app.use("/students", studentRouter) won't map any endpoints to that route.

3. Route Files Not Committed to Git #

If you forgot to add your routes folder or individual route files to Git, Heroku won't deploy them at all.

• Run git status locally to check if any route files are listed as "untracked".
• If so, add them with git add routes/, commit with git commit -m "Add all route files", then redeploy to Heroku.

4. Environment Variable Checks (Less Likely for 404s, But Worth Confirming) #

While 404s usually aren't database-related, a failed DB connection might break routes that depend on it (though that would typically throw 500 errors, not 404).

• Verify all environment variables are set correctly on Heroku: Run heroku config in your terminal to see the full list. Ensure MYSQL_REMOTE_USER and MYSQL_REMOTE_PASS match your local setup.
• Double-check the hardcoded host and database values in your MySQL connection—make sure they're the correct public addresses from Clever Cloud (no typos!).

5. Dig Into Heroku Deployment Logs #

The best way to spot hidden issues is to check Heroku's logs:

• Go to your Heroku app dashboard → Click "More" → "View logs".
• Look for red flags like:
  • "Cannot find module './routes/teachers'" (means a route file is missing)
  • "Error: connect ECONNREFUSED" (database connection failure)
  • Any startup errors that prevent your app from loading all routes.

Quick Test to Confirm Your App is Running #

To rule out static files overriding your / route, modify your indexRouter to return a unique message:

// In routes/index.js
router.get('/', (req, res) => {
  res.send('My API is live on Heroku!');
});

Redeploy and visit /—if you see this message, your app is running, and the issue is definitely with how other routes are being loaded.

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