Nginx反向代理Express时出现Cannot GET错误的问题咨询

Let's walk through the most common fixes for this issue—since you've already set up HTTPS for your sites and are trying to proxy requests to your non-HTTPS Node server, the "Cannot GET" error almost always boils down to routing mismatches between Nginx and Express, or misconfigured proxy settings.

1. Fix Your Nginx Reverse Proxy Configuration #

The biggest culprit here is usually missing or misplaced trailing slashes in your proxy_pass directive. Here's a correct example to add to your existing HTTPS site's Nginx server block:

# Inside your HTTPS server block for the site that needs to call the mail server
location /mail-api/ {
    # Forward requests to your Node server's address/port
    proxy_pass http://localhost:3000/;
    # Important headers to pass along to Express
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;  # Tells Express the original request was HTTPS
}

Key Note: The Trailing Slash #

If your location ends with /, your proxy_pass must also end with /. This tells Nginx to strip the /mail-api/ prefix from the request path before forwarding it to Express. Without the trailing slash, Nginx would send the full path (e.g., /mail-api/send instead of just /send), which your Express server doesn't have a route for—hence the "Cannot GET" error.

2. Verify Your Express Routes Match the Forwarded Paths #

Make sure your Express routes are listening for the paths that Nginx is sending. For example:

• If Nginx forwards /mail-api/send to /send (thanks to the trailing slash), your Express route should be:

  app.post('/send', (req, res) => {
      // Your mail sending logic here
      res.status(200).json({ success: true });
  });
  

• If you accidentally set up Express routes with the /mail-api/ prefix, you'd need to remove the trailing slash from proxy_pass (but the first approach is cleaner, keeping your Node server agnostic of the proxy prefix).

3. Confirm Your Node Server is Listening Correctly #

Double-check that your Express server is listening on the right address and port (matching what's in your Nginx proxy_pass):

// Make sure you're listening on localhost (or 0.0.0.0 for broader access)
app.listen(3000, 'localhost', () => {
    console.log('Mail server running on http://localhost:3000');
});

Avoid listening only on a public IP unless necessary—localhost is safer for internal proxy requests.

4. Test the Proxy Directly #

To isolate whether the issue is with Nginx or Express, run this curl command directly on your Droplet:

curl http://localhost/mail-api/send -X POST -H "Content-Type: application/json" -d '{"to":"test@example.com"}'

• If you get a 404 here: Check your Nginx config (run sudo nginx -t to validate syntax, then sudo nginx -s reload to apply changes) and your Express routes.
• If you get a successful response: The proxy is working, and the issue is with your frontend's request path (make sure it's calling https://your-site.com/mail-api/send instead of the old non-HTTPS Node server address).

5. Optional: Handle CORS (If Needed) #

While this isn't directly related to the "Cannot GET" error, if you run into CORS issues after fixing the proxy, add a CORS middleware to Express:

const cors = require('cors');
app.use(cors({ origin: 'https://your-site.com' })); // Restrict to your HTTPS site

内容的提问来源于stack exchange，提问作者milo