Thursday 31 January 2013

Stack Traces and Error Objects

A frequently requested feature has been that of stack traces with errors. However, because window.onerror, doesn't give access to an error object, it has not been possible for Errorception to capture stack traces. That's set to change today.

Starting today, you will be able to pass error objects to Errorception. An example is probably the best way to explain this.

try {
    var myObject = JSON.parse(jsonString); // will break if jsonString is invalid
} catch(e) {
    throw e;

When you pass such errors manually to Errorception, Errorception will now be able to record the stack trace for this error. Undoubtedly, this can be very useful for debugging.


  • What you push to _errs should be a valid Error object, that is, it should be an instanceof Error.
  • It is important that you throw the error right after passing it to _errs. This is for two reasons. Firstly, you really want your program's execution to stop when you encounter an error, and throw is a great way to do so. Secondly, Errorception internally uses both the Error object and the data from window.onerror to capture error data. If you don't throw the error, Errorception will ignore the error object. Update: Throwing errors isn't required anymore, but is highly recommended.

As an additional bonus, with the exception of Firefox and Safari, you will also get the column number of your error. This is especially important since your JS is likely minified without line-breaks. This column number information is especially exciting — it's likely to guide the future features of Errorception.

Bonus: This works perfectly well with the recently launched ability to record custom information with errors. For example, in Errorception I was recently doing this (yes, Errorception uses Errorception):

try {
    var myObject = JSON.parse(jsonString);
} catch(e) {
    _errs.meta = {json: jsonString};
    throw e;

Friday 11 January 2013

Your JS Errors Are Now An API Call Away

It always annoys me when data gets caught in inaccessible silos, yet that's exactly what I had ended up building with Errorception. Today, that gets rectified.

Today I'm announcing the first cut of the Errorception API. As far as I know at least, it is the first API in the wild tailored specifically for JS errors in your site.

Being a huge fan of simplicity, the API is really simple to use too. In fact, I've embedded a curl example right here in this blog post:

$ curl -i
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Content-Length: 77
Connection: keep-alive


You can view detailed API documentation on the API docs page.

I'm excited to see what you will do with this data. I'm hoping to evolve this API based on what your experience is like. As usual, feel free to mail me at rakeshpai at errorception dot com with any suggestions or feedback.

Sunday 6 January 2013

Improving Daily Emails

The daily notification email, which had been turned off for some time now due to a snag, has now been turned back on.

Previously, all the emails used to be sent at the turn of the day on the server. This was problematic in at least two ways.

  • The load on the DB to sift through the large volume of errors to generate emails was turning out to be a bit much. The server had begun to protest about the load.
  • All users got emails at the same time, irrespective of which timezone they belonged to. I would personally prefer to get my error notification in the morning when I'm starting my day, so that I can schedule time for fixing it. A mail that lands up in my mailbox when I'm about to go to bed is useless at best, and worrisome at worst.

Turns out, solving the latter problem solved the former problem as well, because the server load of sending out the email would get more-or-less evenly distributed across the entire day. So, taking inspiration from what Stride did recently, I've rolled out something similar for Errorception.

A small JS snippet notes your timezone every time you use Errorception. This timezone information is passed along to the server and recorded against your records. A cron kicks in every half hour on the server to determine if you should be sent an email to right now, based on whether it is 9:30 AM in your timezone, using the excellent 'time' module by Nathan Rajlich (TooTallNate). It just works!

So, starting about 15 mins ago, you should now receive emails at 9:30 in the morning, irrespective of which timezone you are in, or whether it's daylight savings or not. If you still aren't receiving emails, get in touch at rakeshpai at errorception dot com.

Almost forgot: Wish you a great 2013! Happy debugging!