How can you limit the allowed execution time of specific methods in the python version of Google App Engine?

Question

由于python版本的Google App Engine不支持信号模块，如果方法在不到2秒内没有返回，调用方法和抛出/捕获异常的最简单方法是什么？

Answer 1

If you are talking about RPC calls, such as the datastore, you can create an RPC with a deadline (see create_rpc ), pass the RPC to your datastore function ( db.get , db.put , etc...), then catch DeadlineExceededErrors .

# Set a five-second timeout
rpc = db.create_rpc(deadline=5)

# A query:
query = YourModel.all().fetch(100, rpc=rpc)

The URLFetch fetch function also takes a deadline parameter.

For your own code you could implement checking yourself, see the time module.

Answer 2

In loops, you can store the time the loop started and check how long it's been going on each iteration.

If you're not in a loop, things are a bit trickier. You could add the time-checking bit every few lines of code. This, of course, makes for really ugly code, but without the ability to spawn threads that could run a timer in the background and interrupt the running code, there's not much of a way around it.