I have a web application with a great deal of both client-side and server-side logic. It is considered business-critical that this application feel responsive to the end user, for some definition of “feels responsive.” 😉
Most website monitoring discussions revolve around keeping an eye on server-side metrics (response time, I/O queue depth, latency, CPU load, etc.), i.e. we tend to treat server performance and responsiveness as though it’s a viable “proxy” for what the user is experiencing.
Unfortunately, as we move more and more logic to client side Javascript, the correlation decreases and our server metrics become less useful.
I didn’t find any good matching SO questions on this. Googling gives a range of commercial products that might be related, but they’re generally from the manufacturers’ websites, full of unhelpful marketspeak and “please call us for details,” so it’s hard to know.
Are there any commonly-used tools for this sort of thing, other than rolling your own? Both free and commercial are welcome, although free is obviously better all else being equal.
EDIT: To clarify, I primarily need to gather bulk data on the user experience, including both responsiveness and breakage/script errors. Automatic analysis is a very-nice-to-have, although I’d expect to have to occasionally dig into the data myself regardless of the solution.
There are some freely available tools for performance monitoring. Yahoo open-sourced a script they used called Boomerang which can measure page load times and other performance metrics for end-users. Full documentation here. Google analytics also offers a basic page load time report.
For error monitoring, you’ll want to listen for the window.onerror event. I don’t know of any scripts that will automatically log it for you, or mine the logs on the server side. If you implement your own, you’ll want to be very careful about not pinging the server too often–imagine how many requests it would generate if there was a JS error in your JS error handling code!