使用ExecutorService控制任务执行顺序 [英] Controlling Task execution order with ExecutorService

问题描述

我有一个进程将异步任务委托给线程池。我需要确保某些任务按顺序执行。
例如

I have a process which delegates asynch tasks to a pool of threads. I need to ensure that certain tasks are executed in order. So for example

任务按顺序到达

任务a1，b1，c1，d1， e1，a2，a3，b2，f1

Tasks a1, b1, c1, d1 , e1, a2, a3, b2, f1

任务可以以任何顺序执行，除非有自然依赖性，所以a1，a2，a3必须在

Tasks can be executed in any order except where there is a natural dependancy, so a1,a2,a3 must be processed in that order by either allocating to the same thread or blocking these until I know the previous a# task was completed.

目前它不使用Java并发软件包，但我'

Currently it doesn't use the Java Concurrency package, but I'm considering changing to take avantage of the thread management.

有没有人有类似的解决方案或建议如何实现这

Does anyone have a similar solution or suggestions of how to achieve this

推荐答案

当我这样做过去，我通常有一个组件，然后提交callables / runnables到执行器的处理。

When I've done this in the past I've usually had the ordering handled by a component which then submits callables/runnables to an Executor.

有类似的东西。

• 有运行的任务列表，有些包含依赖关系


• 使用ExecutorCompletionService创建执行器和换行


• 搜索所有没有依赖关系的任务，通过完成服务计划


• 轮询完成服务


• 随着每个任务完成
  
  
  
  
  • 将其添加到完成列表
  
  
  • 重新评估任何等待任务wrt到完成列表，看看他们是否依赖完成。
  
  
  • Got a list of tasks to run, some with dependencies
  • Create an Executor and wrap with an ExecutorCompletionService
  • Search all tasks, any with no dependencies, schedule them via the completion service
  • Poll the completion service
  • As each task completes
    • Add it to a "completed" list
    • Reevaluate any waiting tasks wrt to the "completed list" to see if they are "dependency complete". If so schedule them
    • Rinse repeat until all tasks are submitted/completed

    完成服务是一个很好的方法，能够获得任务，因为他们完成，而不是试图调查一堆期货。但是，您可能希望保留一个 Map ，当任务通过完成服务计划时填充，以便当完成服务给您一个完整的未来你可以知道 TaskIdentifier 是什么。

    The completion service is a nice way of being able to get the tasks as they complete rather than trying to poll a bunch of Futures. However you will probably want to keep a Map<Future, TaskIdentifier> which is populated when a task is schedule via the completion service so that when the completion service gives you a completed Future you can figure out which TaskIdentifier it is.

    如果你发现自己处于任务仍在等待的状态运行，但没有任何正在运行，没有可以安排，那么你有一个循环依赖的问题。

    If you ever find yourself in a state where tasks are still waiting to run, but nothing is running and nothing can be scheduled then your have a circular dependency problem.

    这篇关于使用ExecutorService控制任务执行顺序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！