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2015/06/03

Testing AJAX APIs with Perl

In my lab, we have an AJAX-laden web tool which loads a certain JSON API on page load. It was judged that what we had was too slow, so I created a program that wrote that JSON to a static file on regular intervals. Problem with that, of course, is that changes to the data would not show up in the static file until the next scheduled update.

So, we created a third version, which checks the database for checksum, and if it changes, it regenerates the file and sends the data. Otherwise, it opens the file and sends the data.

I tested with Chrome Dev Tools, which told a bit of the story, but at the scale where it's closer to anecdotes than data. I wanted to go into the hundreds of hits, not just one. I pulled out Benchmark, which told a story, but wasn't quite what I wanted. It started the clock, ran it n times, then stopped the clock, while I wanted to get clock data on each GET.

I also realized I needed to test to be sure that the data I was getting was the same, so I used Test::Most to compare the object I pulled out of the JSON. That was useful, but most useful was the program I wrote using Time::HiRes to more accurately grab the times, then use Statistics::Basic and List::Util to take the collected arrays of sub-second response times and show me how much faster it is to cache.

And it is fairly significant. The best and worst performance were comparable, but the average case has the cached version being about twice as fast, and using the static file being about 7 times faster. With, of course, the same problems.

If I wasn't about to take time out of the office, I'd start looking into other methods to get things faster. Good to know, though, that I have the means to test and benchmark it once I get back next week.