For some reason, our TG app was leaking transactions, causing predictable crashes. Every page view, Postgres was holding onto transaction, which never committed.
Argh.
After much brute force debugging, I discovered the problem. A controller was calling a method in the model, and passing the return value through to the template, where incidentally, the value was no longer being used. "Easy fix", I thought, "just remove the method call."
But, I couldn't leave it at that, I had to find out what this method was doing differently which was causing transaction leakage... As it turns out, the method was returning a generator, via a generator expression. The generator itself was holding references to the transaction, preventing it from closing. The transaction would only close once the generator had been iterated through completely, finally calling the clean up code.
Woohoo. It's a good feeling when you kill a nasty bug like this. I'll be more careful with generator expressions from now on!
Subscribe to:
Post Comments (Atom)
Popular Posts
-
These are the robots I've been working on for the last 12 months. They each weigh about 11 tonnes and have a 17 meter reach. The control... -
This hard-to-see screenshot is a Generic Node Graph Editing framework I'm building. I'm hoping it can be used for any kind of node... -
Unfortunately I've not secured a venue for the GGJ. With 9 days left, things are not looking hopeful. It could be that GGJ Perth will no...
-
So, you've created a car prefab using WheelCollider components, and now you can apply a motorTorque to make the whole thing move along. ... -
MiddleMan: A Pub/Sub and Request/Response server in Go. This is my first Go project. It is a rewrite of an existing Python server, based o...
-
Often, when building a game, you need to test if objects are colliding. The objects could be spaceships, rocks, mouse pointers, laser beams....
-
I've just read a newspaper article (courtesy of Kranzky ) from WA Business News documenting the malfeasance, gross negligence and misc...
-
After my last post, I decided to benchmark the scaling properties of Stackless, Kamaelia, Fibra using the same hackysack algorithm. Left axi... -
Update: This is another planet shader, with more physical fidelity. Shader "Planet" { Properties { _MainTex ("Diff... -
Possibly slightly more correct lighting. The rim light is now only applied in the direction of the sun, rather than being purely based on vi...
2 comments:
Sounds like the real problem is relying on garbage collection to do your finalisation, instead of explicitly closing the transaction at the end of the web request.
Yeah, thats the issue in a sentence. In theory TG is supposed to look after this. It's think it is probably another symptom of SQLAlchemy having second-class support in TG, though I haven't investigated any further yet.
Post a Comment