Crash Detection

 Tonight I was working on a bug you may have seen that is sneaky, so I wanted to blog about it quick and let you know I have a basic fix inbound.

First let's start with the symptom. Have you ever had Wingman Jr. loaded and running in the browser for a while, but then it just seems like questionable stuff starts slipping through and the addon might not be working? (You may have seen this an image- or video-intensive site like Imgur.) You can see the issue over at GitHub.

Well, your hunch is correct! But the way in which it is failing is interesting. Some part of either Firefox or Tensorflow.js crashes. But the end result doesn't crash the whole addon, which would cause a reload. No, instead it simply causes the model prediction results to be incorrect. I've most often seen it send all zeroes back for the model prediction, which turns into "safe".

So to fix this I needed to get a bit creative. The addon will now routinely check itself by using a "watchdog" function. It uses one of the silent mode images already packed into the plugin and checks that the prediction results for that image are the same every so often. If they aren't, the "watchdog" checker will give it another chance or so, and then automatically reload the plugin. To make things a little bit performant for your computer, it will temporarily stop checking when Firefox thinks that the user is idle.

Fortunately this solution seems to be fairly reliable so far in testing, but does have the downside that it may cause a pause during the automatic addon reload. Do note that reloading the addon will cause it to go back to its default automatic mode. If preserving this is important to you, please let me know via an issue in Github or in the feedback link in Wingman Jr. itself.