问题
is there a way to determine when a set of Google App Engine tasks (and child tasks they spawn) have all completed?
Let's say that I have 100 tasks to execute and 10 of those spawn 10 child tasks each. That's 200 tasks. Let's also say that those child tasks might spawn more tasks, recursively, etc...
Is there a way to determine when all tasks have completed? I tried using the app engine pipeline API, but it doesn't look like it's going to work out for my particular use case, even though it is a great API.
My use case is that I want to make a whole bunch of rate limited URL fetch calls while concurrently writing to a blob. At the end of all the URL fetch calls, I want to finalize the blob.
I found the solution with the pipeline API, but it does so much writing to the datastore that it wouldn't be cost effective for me with how often I need to run the pipeline.
回答1:
There's no way around writing to a persistent storage medium of some sort, and the datastore is the only game in town. You could write your own server to track completions using a backend, but that's an awful lot of overhead for a simple task. Using the pipeline API is your best bet.
来源：https://stackoverflow.com/questions/9027757/is-there-a-way-to-know-when-a-set-of-app-engine-task-queue-tasks-have-completed