Schrödinger's Cache: a debugging law of physics

[exxos]

There is a principle every developer and hardware engineer eventually discovers, and it is far more reliable than anything in the textbooks:

A fault will occur every few minutes — right up until the moment you start watching for it.

Call it Schrödinger's Cache. The bug exists in a superposition of "completely broken" and "working perfectly", and the waveform collapses to "working perfectly" the instant you attach a debugger, enable logging, or open an incognito window to check.

It has a sibling in the famous double-slit experiment: a particle behaves one way until you measure it, then behaves differently purely because you looked. Your server does exactly the same thing:

• Tail the log live, and the errors politely stop.
• Add a debug header to catch the culprit, and the culprit quietly retires.
• Sit and watch the dashboard, and the load average flatlines as if offended you ever doubted it.

Hardware people know it best of all. The intermittent fault that has plagued a board for a week vanishes the instant the oscilloscope probe touches the pin — because, of course, the probe's capacitance just changed the timing enough to mask it. A Heisenbug in the truest sense: you cannot measure it without altering it.

The cruel corollary: it resumes the moment you stop watching. Close the log, walk away, and the failures return — having waited, patiently, for you to look away.

They say if you leave a terminal open tailing the log overnight, the bug never fires again, and the log fills only with the quiet sound of a system that knows it is being observed.

So if your forum, your server, or your circuit board is misbehaving and you simply cannot catch it in the act — congratulations. It is not a bug.

It is physics.

:dizzy:

[alexh]

As you say, in software looking usually changes the conditions of the test

In hardware as we can look at everything at once, without disturbing the conditions of the test fortunately for HW engineers debugging a failure doesn't have any such issues and closure is much faster

[rubber_jonnie]

I like the change to Schrodingers Cache :)

Might have to start using that at work :)

Typically in my work we do all we can to avoid upsetting systems whilst we grab diagnostic data, but it's never perfect.

[Darklord]

Hilarious. Forwarding to friends who code. :lol:

[Darklord]

This actually reminds me of my "round and round it goes" experience
with the ALTMON program for my STorm-ST board.

I mean, change made, it works! Eureka! Pack everything away

waiting-spongebob.gif

Right back to square one - not found! memory not installed!

Wash...rinse...repeat. :lol:

[exxos]

Right back to square one.. Wash...rinse...repeat. :lol:

Story of my life :lol: :roll: