DEV Community

Cover image for The Radar Gun Problem
Conlin Durbin
Conlin Durbin

Posted on • Originally published at on

The Radar Gun Problem

The other day, I was driving home from an event and there was a massive slowdown on the highway. I assumed that there was a crash or some construction up ahead, but as I got closer to the bottleneck, I realized that the only difference was that there was a cop standing on the side of the highway with a radar gun. Just the presence of a monitor slowed down the performance of the system.

Later that week, I was debugging some Javascript code and ran into a problem I have hit a few times. I had a fairly intensive process looping over a lot of values. I took the standard approach to debug a JS problem and dropped in a console.log. I refreshed the page, opened the console... and almost crashed my browser.

Calling a console.log with an intensive process takes a lot of memory, it turns out. I've run into this before, but this time the traffic slowdown really made me think about it. Let's talk a bit about something I'm calling the RadarGun Problem.

In many situations, the fix for the problem is changing where the observation happens. Moving the console.log outside of the loop - either after or before -is a good option. You can also change the method of observation - drop in adebugger; and step through it, introducing a purposeful bottleneck to prevent an accidental one.

Have you run into this before? How have you solved it?

Top comments (1)

tchaflich profile image
Thomas C. Haflich

Seems like a variant of the Heisenbug.

Usually when I come across one, I end up having to refactor something anyway - whatever was janky enough to make me want to test it is usually janky enough to break apart into more easily testable pieces when it slows down or does something weird.