3 ms·

In what scenario would you anticipate data for the calculation of rotation speed and engine thrust for one particular plane to be based on a value that is not o

In what scenario would you anticipate data for the calculation of rotation speed and engine thrust for one particular plane to be based on a value that is not only shared and writable, but changing each time a plane's performance data is calculated? "multiple data streams feeding in weight data per aircraft"? What does that word salad even mean? Even if what any of what you said was true: these developers are writing critical safety software. If they can't manage to write code without generating race conditions and testing their system for such conditions, they are grossly unqualified to be writing this sort of software. As others have said: this is a huge fuck-up.

Jtsummers 4y ago
It is a huge fuckup, I didn't say otherwise. And that's not word salad, though maybe not as clear as I could have made it. But to clarify for this hypothetical (if this is the issue): Each luggage weigh station submits data to the application or database which then has to tally the weight. Those are multiple data streams, not a hard concept. An airport has many luggage weigh stations all potentially submitting data at the same time. If those are being processed concurrently and the database or however the data is stored is not properly locked then the tally can be incorrect for the same reason non-atomic increments/decrements can become incorrect in a multithreaded application. But just like the problem with non-atomic (unlocked) increments/decrements the problem may not manifest without high enough load on the system. Low-load testing (what the article seems to describe) means that updates can happen fast enough (server or application is under loaded, less likely to interrupt any update) or submitted slow enough that the issue never appears. So you need to test with a higher load to detect the problem (if you're going to be able detect it in testing at all).
richwater 4y ago
I fucking cracked up at: "multiple data streams feeding in weight data per aircraft" it's literally some integers (floats at the worst?).
- Dylan16807 4y ago
  You can send integers from multiple sources, dude.

Jtsummers 4y ago

It is a huge fuckup, I didn't say otherwise. And that's not word salad, though maybe not as clear as I could have made it. But to clarify for this hypothetical (if this is the issue): Each luggage weigh station submits data to the application or database which then has to tally the weight. Those are multiple data streams, not a hard concept. An airport has many luggage weigh stations all potentially submitting data at the same time. If those are being processed concurrently and the database or however the data is stored is not properly locked then the tally can be incorrect for the same reason non-atomic increments/decrements can become incorrect in a multithreaded application. But just like the problem with non-atomic (unlocked) increments/decrements the problem may not manifest without high enough load on the system. Low-load testing (what the article seems to describe) means that updates can happen fast enough (server or application is under loaded, less likely to interrupt any update) or submitted slow enough that the issue never appears. So you need to test with a higher load to detect the problem (if you're going to be able detect it in testing at all).

richwater 4y ago

I fucking cracked up at: "multiple data streams feeding in weight data per aircraft" it's literally some integers (floats at the worst?).

Dylan16807 4y ago
You can send integers from multiple sources, dude.