如何判断一组App Engine任务是否已全部完成? [英] How can I tell if a set of app engine tasks have all completed?

问题描述

如果我有一个循环，其中有100个任务入队，而每个任务都可能有一个任务入队，我怎么知道所有任务是否都已完成?

If I have a loop that enqueues say 100 tasks and each one of those tasks potentially enqueues a task, how can I tell if all tasks have completed?

我已经考虑过使用ShardedCounters解决此问题.完成每个任务后，我可以增加一个计数器，然后检查是否count ==100.当然，除非我进入这种递归计数方案，否则任务会产生自己的任务.我不确定掉进那个兔子洞是个好主意，因为分片的计数器似乎不是原子的.

I've thought about this problem using ShardedCounters. Once each task is completed, I could increment a counter then check to see if count == 100. Of course that falls apart with tasks spawning their own tasks unless I get into this recursive counting scenario. I'm not sure it's a good idea to go down that rabbit hole because it appears the sharded counters are not atomic.

推荐答案

您应该看看新的AppEngine 管道API .这是将昂贵的任务链接在一起并通知它们何时完成的一种方式.还有一个很棒的来自Google IO的视频会议进行演示.

You should take a look at the new AppEngine pipeline API. It's a way of chaining together expensive tasks, and notifying when they're complete. There's a also great video from the Google IO conference which demonstrates it.

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