how to stop node js server from crashing

Question

I am new to node js. I was trying to create a simple HTTP server. I followed the famous example and created a 'Hello World!' server as follows.

var handleRequest = function(req, res) {
  res.writeHead(200);
  res1.end('Hello, World!\n');
};

require('http').createServer(handleRequest).listen(8080);

console.log('Server started on port 8080');

Running this code would start the server properly as expected. But trying to access http://127.0.0.1:8080 would crash it by throwing an error that res1 is not defined. I would like to have the server still continue running and gracefully report errors whenever it encounters it.

How do I achieve it? I tried try-catch but that isn't helping me :(

Answer 1

There are a bunch of comments here. First of all, for your example server to work, handleRequest needs to be defined BEFORE using it.

1- What you actually want, which is preventing the process to exit, can be handled by handling uncaughtException ( documentation ) event:

var handleRequest = function(req, res) {
    res.writeHead(200);
    res1.end('Hello, World!\n');
};
var server = require('http').createServer(handleRequest);
process.on('uncaughtException', function(ex) {
    // do something with exception
});
server.listen(8080);
console.log('Server started on port 8080');

2- I would recomment to use try{} catch(e) {} on your code, such as:

var handleRequest = function(req, res) {
    try {
      res.writeHead(200);
      res1.end('Hello, World!\n');
    } catch(e) {
      res.writeHead(200);
      res.end('Boo');
    }
};

3- I guess the example was just an example and not actual code, this is a parsing error that can be prevented. I mention this, since you NEED to NOT have parsing errors on Exception catch handlers.

4- Please note that node process is going to be replaced in the future with domain

5- I'd rather use a framework like express , than doing this stuff.

6- Recommended lecture: StackOverflow - NodeJS best practice for exception handling

Answer 2

I am not targeting your question details but your question's title about preventing Node server from crashing. You can probably use DOMAIN , this will probably stop your server from crashing when an uncaughtException is thrown.

domain = require('domain'),
d = domain.create();

d.on('error', function(err) {
  console.error(err);
});

for more details go http://shapeshed.com/uncaught-exceptions-in-node/

beside using this method must try-catch your block.

Answer 3

Maybe you should define handleRequest before you use it:

require('http').createServer(handleRequest).listen(8080);

function handleRequest(req, res) {
  res.writeHead(200);
  res1.end('Hello, World!\n');
};

Or

var handleRequest = function(req, res) {
  res.writeHead(200);
  res1.end('Hello, World!\n');
};

require('http').createServer(handleRequest).listen(8080);

---

And you should be sure that res1 also exists.