在队列中查找已生成的任务的策略

Question

I am writing a module where a number of threads will be spawned which performs some task. So overall I have a 'Manager' class which provides information to a 'Resolver' class which create and submits a 'Task' using threadpool.

Resolver has a threadpool executor which has unbounded queue that I am using to check if perticular task is already spawned. If there is already an instance of the task in the queue, I remove it using ThreadPoolExecutor and submit a new task again. This is done intentionally since new task brings new info from the 'Manager'.

I am using ThreadPoolexecutor to find if the task is already is queue. But I am worried about the performance of the queue and feel that hash map would be a better choice since queue might have more than 30000 instances of task.

Guide me to choose an appropriate strategy for finding already spawned task in queue.

Answer 1

I don't think it would cause any problems (unless you implement too complicated equals implementation). I would recommend to run a test with profiler and take a look if it is a real problem or not...

However if it is, you might create your own implementation of BlockingQueue (it might be passed into ThreadPollExecutor as a contructor argument). This way you might create some sort of hybrid some implementation of BlockingQueue (for standard work queue) and HashSet (for fast contains(...) test). Remember about proper synchronization for all operations on those collections. All operations must be atomic.