Question

我要实现以下行为：

从文件中读取n个事件
在n个线程中处理它们
如果仍有任何事件，请返回步骤1

我编写了以下应用来测试解决方案，但它在随机时刻失败，例如。

java.lang.IllegalStateException: Failed to execute CommandLineRunner
Caused by: org.springframework.core.task.TaskRejectedException: Executor [java.util.concurrent.ThreadPoolExecutor@62b3df3a[Running, pool size = 5, active threads = 4, queued tasks = 0, completed tasks = 70]] did not accept task: java.util.concurrent.CompletableFuture$AsyncSupply@71ea1fda

如果我不想将事件放入队列，应该设置什么队列容量？我想立即处理它们。

我正在使用Open JDK 11和Spring Boot 2.2.2.RELEASE

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.stream.Collectors;

@SpringBootApplication
public class DemoApplication implements CommandLineRunner {

    @Autowired
    private ThreadPoolTaskExecutor eventExecutor;

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Bean(name = "eventExecutor")
    public ThreadPoolTaskExecutor eventExecutor() {
        ThreadPoolTaskExecutor pool = new ThreadPoolTaskExecutor();
        pool.setCorePoolSize(5);
        pool.setMaxPoolSize(5);
        pool.setQueueCapacity(0);
        pool.setAwaitTerminationSeconds(0);
        pool.initialize();
        return pool;
    }

    @Override
    public void run(String... args) {
        System.out.println("Start events processing");
        long start = System.currentTimeMillis();

        int result = 0;
        for (int i = 0; i < 100; i++) {
            List<CompletableFuture<Integer>> completableFutures = getEvents(5).stream()
                    .map(event -> CompletableFuture.supplyAsync(() -> processEvent(event), eventExecutor))
                    .collect(Collectors.toList());

            result += completableFutures.stream()
                    .mapToInt(CompletableFuture::join)
                    .sum();
        }

        long timeMillis = System.currentTimeMillis() - start;

        System.out.println("Took " + timeMillis + "ms, " + result);
    }

    private List<Event> getEvents(int n) {
        List<Event> events = new ArrayList<>();
        for (int i = 1; i <= n; i++) {
            events.add(new Event(i));
        }
        return events;
    }

    private int processEvent(Event event) {
        System.out.println("processing event " + event.id);

        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("processing event " + event.id + " finished");

        return 1;
    }

    private static class Event {

        private int id;

        private Event(int id) {
            this.id = id;
        }
    }
}

Answer 1

我建议更改pool.setQueueCapacity(0)以使用正值，以使在如此配置的固定大小池中没有可用线程时将任务排队等待处理（corePoolSize == maxPoolSize = = 5）。

输出“池大小= 5，活动线程= 4”显示active threads的近似个数字。

从理论上讲，在尝试处理新一批事件之前，线程可能不会返回到池中。

ThreadPoolTaskExecutor抛出RejectedExecutionException

1 个答案:

ThreadPoolTask​​Executor抛出RejectedExecutionException

1 个答案:

ThreadPoolTaskExecutor抛出RejectedExecutionException