如何使用Google App Engine任务队列以（FIFO）顺序执行任务？ [英] How to execute tasks in (FIFO) order using Google App Engine Task Queues?

问题描述

我相信Google App Engine中的任务队列（push，pull，deferred）并不能保证任务将以FIFO的顺序执行。例如，假设我有一个任务队列，任务A，B和C，每个任务都有时间戳t_A，t_B和t_C，这样t_A< t_B< T_C。我如何确保按照时间戳顺序执行任务A，B和C？如果任务B失败，我想推迟任务C的执行直到任务B成功执行。我已经看到了一个ETA字段来设置一个任务可以发送的最早时间，但是这看起来更像是一种启发式的，而不是一种保证。

解决方案

考虑使用Pipelines API：

https://github.com/GoogleCloudPlatform/appengine-pipelines

他们已经为您完成了这项工作：

https：// github.com/GoogleCloudPlatform/appengine-pipelines/wiki/Python#user-content-execution-ordering

  class LogWaitLogInOrder（pipeline.Pipeline）：
 
 def run（self，message1，message2，delay）：
 with pipeline.InOrder（）：
产生LogMessage（message1）
产量延迟（秒=延迟）
产量LogMessage（消息2）
 
产量LogMessag e（'这会在运行时立即发生'）
  

管道api还为您提供报告/反馈/通知/等。

但是，如果这对您的特殊需求是过度的，那么就像@Paul所建议的那样，只要在第一个任务完成时创建下一个任务，并希望最好的

---

视频参考：

Google I / O 2010 - 使用Google App Engine的数据流水线：
$ b

https://www.youtube.com/watch?v=zSDC_TU7rtc

I believe task queues (push, pull, deferred) in Google App Engine do not guarantee that tasks will be executed in FIFO order. For example, suppose I have a task queue with tasks A, B, and C, and each task has timestamps t_A, t_B, and t_C, such that t_A < t_B < t_C. How can I ensure that tasks A, B, and C are executed in order of timestamp? If task B fails, I would like to delay the execution of task C until task B executes successfully. I've seen an ETA field to set the earliest time that a task can be sent, but this seems like more of a heuristic, not a guarantee.

解决方案

Consider using the Pipelines API:

https://github.com/GoogleCloudPlatform/appengine-pipelines

They have already done the work for you:

https://github.com/GoogleCloudPlatform/appengine-pipelines/wiki/Python#user-content-execution-ordering

class LogWaitLogInOrder(pipeline.Pipeline):

  def run(self, message1, message2, delay):
    with pipeline.InOrder():
      yield LogMessage(message1)
      yield Delay(seconds=delay)
      yield LogMessage(message2)

    yield LogMessage('This would happen immediately on run')

The pipelines api also gives you reporting/feedback/notification/etc.

But if that's overkill for your particular needs, then just do as @Paul suggested, just create the next task when the first one completes and hope for the best

---

video reference:

Google I/O 2010 - Data pipelines with Google App Engine:

https://www.youtube.com/watch?v=zSDC_TU7rtc

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