Java计划执行程序服务功能

Question

I'm designing a server in which I need to be able to schedule thousands of tasks. The task gets executed every 5 seconds. Will the scheduledexecutorservice be able to handle the thousands of tasks with good accuracy? I'm trying to do the timing in just one thread. But the actual tasks will be executed in a thread pool. Thanks

I'm unsure exactly how it works so if anyone could clarify that as well it'd be appreciated!

Answer 1

ScheduledExecutorService is backed by a thread pool. Roughly speaking you can calculate the number of threads required to run tasks concurrently without delays using the following equation:

minimal number of threads in the pool is equal to average number of tasks executed per second times average task run time

For example on average you start 2 tasks taking 3 seconds (on average) to finish, you need 6 threads. Of course this assumes fairly uniform distribution of tasks over time.

You can also use Executors.newCachedThreadPool() which can theoretically run infinite number of tasks concurrently. Obviously available memory and number of context switches will greatly reduce this number.

If your usage scenario is: run thousands of tasks schedule at exact same point in time every five seconds - neither JVM nor any other platform will handle that. Even if you have thousands of threads , you are limited by the number of CPU cores. Accuracy is highly dependent on the nature of your tasks (CPU-intensive? blocking I/O?)

Answer 2

I would suggest that you read the javadocs of scheduler executor service. Is there any particular point that makes you doubt it's Industrial strength. You should use it and measure your performance to check whether it matches your use case.

Also, unless you have strong reason you should not tinker with the implementation of the library class (segregating scheduling and task execution threads on the client side)

However, you should evaluate using a library like quartz if your scheduling criteria are expected to get complicated - beyond the basic use cases provided by the scheduler executor service.