Software Reliability with Dishwashers

Some weeks ago my dishwasher started leaking water in the front. At first, I thought the water filter was full, and after cleaning it properly, the issue didn’t happen anymore.

Until some days ago.

This time it came with much more stubbornness, showing errors on the display. The dishwasher is an AEG, and the error code was looking like a ,10 (yeah, comma included). I googled a bit, and it seems that it means that the dishwasher can’t load any more water. It was quite surprising, as just after a few minutes the cleaning program had started, I was able to clearly hear that the water was flowing through the pipes. Then suddenly silence and that error message.

The QA side of me forced me to randomly press the buttons present on the machine, with some more persistence for the Reset one, hoping it would just heal itself – who knows, maybe it was overwhelmed – pressing F5 typically works 🙂 Strangely enough, the error code disappeared when I pressed the arrow down button, totally unexpected, and the program resumed. I was happy until the dishwasher started leaking water again, and this time another error code appeared: ,30.

I googled again, and I found what seems to be a fail-safe mechanism from the manufacturer to prevent the appliance from leaking too much water – which could be dangerous if there are kids, pets, or cables on the ground, I guess. It seems this is a feature called Aquastop.

That was an interesting finding. I googled (again) a bit to understand how this is all connected together, and I found a short video explaining in five minutes how the Aquastop works. It immediately reminded me of the Circuit Breakers that we use for reliability patterns, for example in microservices.

I like to think that this happens when a team of smart engineers sits down together and tries to solve a real problem in a creative way. It’s astonishing what we can learn from electric engineers, or more specifically, from the products we use on a daily basis, if only we had the time to disassemble stuff and see how it was done. In this case, obviously the product can’t heal itself, because maybe the water hose is perforated, it leaks water, etc., however, the gist of it is this: a simple monitoring tool that sends a signal to stop the water inlet valve, when there is too much of it where it shouldn’t be.

Brilliant.

What’s next? Pingdom for washing machines?

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