AWS Lambda: Express res.render always sends "internal server error"

Question

My goal is to port my existing Node-Express-Pug-Mongo website onto Amazon Web Services, but I'm running into an error with rendering Pug files on Lambda. Whenever I attempt to run res.render, the page shows this: {"message": "Internal server error"} after a timeout of 3000 milliseconds (from viewing the CloudWatch console).

I've tried throwing console.log everywhere to get more information on what is causing the error, but to no avail.

• res.send works with text
• res.sendFile works with the Pug file that I am trying to use in the function
• res.render accepts a callback input, which I have attempted to use to catch errors, but no logs exist on the console.
• I've tried different ways of inputting the pug file, as you can see for the five different get URLs. All of them do the same thing.
• I've tried changing to Jade, but I get the same issues.
• NOTE: On a local server, the syntax in render1 and render3 are the ones that work.
• ALSO: On the local server, using callbacks does cause the function to hang. I have attempted this with and without callbacks, and the issue is the same.

'use strict'
const path = require('path');
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
const router = express.Router();

app.set('view engine', 'pug');

router.use(bodyParser.json());
router.use(bodyParser.urlencoded({ extended: true }));
app.set('views', path.join(__dirname, 'views'));

router.get('/sendfile', function(req, res){
    res.sendFile(__dirname+"/views/test.pug");
});

router.get('/sendtext', function(req, res){
    res.send('hello!');
});

router.get('/render1', function(req, res){
    res.render('test', {}, function(err){
        console.log(err);
    });
});
router.get('/render2', function(req, res){
    res.render('.test', {}, function(err){
        console.log(err);
    });
});
router.get('/render3', function(req, res){
    res.render('./test', {}, function(err){
        console.log(err);
    });
});
router.get('/render4', function(req, res){
    res.render('./views/test', {}, function(err){
        console.log(err);
    });
});
router.get('/render5', function(req, res){
    res.render(__dirname+'/views/test', {}, function(err){
        console.log(err);
    });
});
app.use('/', router);

// Export your express server so you can import it in the lambda function.
module.exports = app;

None of these render functions work. It always times out after 3 seconds and returns {"message": "Internal server error"}. I've tried everything I could think of. Is this an Express issue? Do I have to do something different to configure Pug? It works exactly as expected when I use the exact same module on a local Node.js server.

Answer 1

After a lot of digging, I figured out the issue. My Lambda function ("server") wasn't allocated enough RAM. When I attempted to load Pug, it would overload and crash. The default is 128MB, so turning it up to 384MB-ish worked fine.