Get ready, because today we're tackling Bug #2, which caused us quite a bit of anxiety and made us question the stability of even the most reliable tools. This story took place in 2021, when I was working on a project with a backend in .NET and a database PostgreSQL. We used Entity Framework Core and Npgsql to interact with the data. Sounds like a standard, unremarkable stack, right? Well, hold on tight!
Phantom Steps and Mysterious Interventions
Sometimes, at the most unexpected moments, the application would start throwing a cryptic error while executing database queries. The error message was so vague that it was infuriating: it indicated a "unexpected result after executing a certain step of the query." Imagine a query as a sequence of steps: 1, 2, 3... But we were getting results as if step 3 had been executed after step 1! It was like an invisible entity was interfering with the query execution process, brazenly disrupting its logical flow.
The Hunt for a Race Condition: A Mission Impossible?
The application code was scrutinized from top to bottom, under a microscope, with meticulous attention – not a single hint of a race condition! This was particularly frustrating, because "races" are usually the culprits behind such strange behavior. Moreover, the error was a real ghost – it only occurred very rarely, once every few hours, and only under high load. This made catching it like searching for a needle in a haystack that was constantly being moved around.
The Solution: Secrets of Npgsql Keepalive and Unexpected Surprises
And so, after several days (literally days!) of intense debugging and exploring every possible hypothesis, we finally got a lead! It turned out that the frequency of the error was affected by... the keepalive parameter in Npgsql – that very function that automatically keeps the connection active. And the most surprising thing: as the keepalive value decreased, the frequency of errors INCREASED!
Armed with this knowledge, I dove into the depths of the Npgsql source code. And there, in those digital catacombs, I discovered that keepalive, in the context of concurrency, is not 100% reliable. It turned out that this problem wasn't just ours! I found a corresponding bug on GitHub, where an active discussion was already underway with the developers (you can check it out yourself – it was fascinating!).
As a temporary solution, we completely disabled keepalive, and the bug was quickly fixed in the next version of the library. Whew!
The Moral of the Story: Bugs Come From Unexpected Places
The main moral of this saga is that a
race condition can creep in from anywhere – even from the most unexpected places! Sometimes you think the problem is in your code, but it's hiding in the depths of a library you never even considered.How often do you encounter such "surprises" in your dependencies? Has a bug ever hidden itself where you least expected it?
#ru #en #bugs