Node.js Best Practice Exception Handling

Question

I just started trying out node.js a few days ago. I\'ve realized that the Node is terminated whenever I have an unhandled exception in my program. This is different than the

Answer 1

Catching errors has been very well discussed here, but it's worth remembering to log the errors out somewhere so you can view them and fix stuff up.

​Bunyan is a popular logging framework for NodeJS - it supporst writing out to a bunch of different output places which makes it useful for local debugging, as long as you avoid console.log. ​ In your domain's error handler you could spit the error out to a log file.

var log = bunyan.createLogger({
  name: 'myapp',
  streams: [
    {
      level: 'error',
      path: '/var/tmp/myapp-error.log'  // log ERROR to this file
    }
  ]
});

This can get time consuming if you have lots of errors and/or servers to check, so it could be worth looking into a tool like Raygun (disclaimer, I work at Raygun) to group errors together - or use them both together. ​ If you decided to use Raygun as a tool, it's pretty easy to setup too

var raygunClient = new raygun.Client().init({ apiKey: 'your API key' });
raygunClient.send(theError);

​ Crossed with using a tool like PM2 or forever, your app should be able to crash, log out what happened and reboot without any major issues.

Answer 2

If you want use Services in Ubuntu(Upstart): Node as a service in Ubuntu 11.04 with upstart, monit and forever.js

Answer 3

I wrote about this recently at http://snmaynard.com/2012/12/21/node-error-handling/. A new feature of node in version 0.8 is domains and allow you to combine all the forms of error handling into one easier manage form. You can read about them in my post.

You can also use something like Bugsnag to track your uncaught exceptions and be notified via email, chatroom or have a ticket created for an uncaught exception (I am the co-founder of Bugsnag).

Answer 4

I would just like to add that Step.js library helps you handle exceptions by always passing it to the next step function. Therefore you can have as a last step a function that check for any errors in any of the previous steps. This approach can greatly simplify your error handling.

Below is a quote from the github page:

any exceptions thrown are caught and passed as the first argument to the next function. As long as you don't nest callback functions inline your main functions this prevents there from ever being any uncaught exceptions. This is very important for long running node.JS servers since a single uncaught exception can bring the whole server down.

Furthermore, you can use Step to control execution of scripts to have a clean up section as the last step. For example if you want to write a build script in Node and report how long it took to write, the last step can do that (rather than trying to dig out the last callback).