有没有办法对本地appengine开发服务器强制执行30秒限制？

Question

Hey, i was wondering if there is a way to enforce the 30 seconds limit that is being enforced online at the appengine production servers to the local dev server? its impossible to test if i reach the limit before going production.

maybe some django middlware?

Answer 1

You could write (and insert in the WSGI stack) a useful piece of WSGI middleware which uses a threading.Timer which logs the fact that the transaction has exceeded 30 seconds (and of course calls cancel on the timer object on the way out, as there's nothing to log in that case).

I'd do it at WSGI level, not Django level, (a) because I'm more familiar with WSGI middleware and (b) because it's a more general solution (it can help a Django web app, but it can also help a web app using any other framework -- WSGI's use is guaranteed by App Engine, whatever framework you decide to lay on top of it).

You'll need to tweak the "30 seconds" a bit to calibrate, because of course the power, available RAM, disk speed, etc, of your development machine, can't just happen to be exactly identical to Google's, and also many subsystems (esp. the storage one) have very different implementations "locally on the SDK" versus "on Google's actual servers" and in any given case may happen to be substantially slower (or maybe faster!-).

Given the considerations in the previous paragraph it might actually be more helpful to have the middleware simply always log the transaction's total elapsed time -- this way you can watch for transactions that (while they may terminate within 30 seconds on your development server) are taking comparable time (say 15 or 20 seconds or more), especially if they have multiple storage transactions that might slow them down on the real production servers/

Answer 2

It's possible , as Alex demonstrates, but it's not really a good idea: The performance characteristics of the development server are not the same as those of the production environment, so something that executes quickly locally may not be nearly as quick in production, and vice versa.

Also, your user facing tasks should definitely not be so slow as to approach the 30 second limit.