Concurrency control and Research

[DevShivmohan]

Controlling the request if at a time n no. of request processing in the Queue then avoid the request if greater than n requests.

• Using ThreadPoolTaskExecutor we can control that request at runtime.
• Declare the bean of ThreadPoolTaskExecutor with n max threads.

  @Bean
  public ThreadPoolTaskExecutor threadPoolTaskExecutor() {
      ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
      executor.setCorePoolSize(10); // Set the core pool size
      executor.setMaxPoolSize(10); // Set the maximum pool size
      executor.setQueueCapacity(10); // Set the queue capacity
      executor.setThreadNamePrefix("MyWorkerThread-");
      executor.initialize();
      return executor;
  }

• Define your task implementation inside the run method.

  class Task implements Runnable{
  @Override
  public void run() {
      try {
          System.out.println("Running Thread Name: " + Thread.currentThread().getName());
          TimeUnit.SECONDS.sleep(20);
          System.out.println("Completed Thread Name: " +Thread.currentThread().getName());
      } catch (InterruptedException e) {
  
      }
  }
  }

• Create or inject the dependency injection of newly created bean ThreadPoolTaskExecutor.
• And implement inside the service layer like below example.

  /**
   * Process the request if queue size less than 10
   * Otherwise block the request
   * @return
   * @throws InterruptedException
   */
  @Override
  public String processRequest() throws InterruptedException {
      // asynchronous processing logic
      if(threadPoolTaskExecutor.getActiveCount()>=10){
          // Throw the exception or blocking the request
          return "Your task rejected because Queue is full as of now";
      }
      threadPoolTaskExecutor.submit(new Task());
      return "Your task is assigned to the worker thread";
  }

[DevShivmohan]

Schedule task using Excecutor service

import lombok.*;

import java.util.*;
import java.util.concurrent.*;

public class CodingTest {
    private final static ScheduledExecutorService scheduledExecutorService=Executors.newScheduledThreadPool(1);
    /**
     *  016 -> Octal
     *  0*8^2 + 1*8^1 + 6*8^0 -> decimal
     *  1+16+64   ->   81
     *  https://dummy.restapiexample.com/api/v1/employees
     * @param args
     */
    public static void main (String[] args) throws Throwable{
        Runnable runnable=new CustomScheduler("task1");
        Runnable runnable1=new CustomScheduler("task2");
        Runnable runnable2=new CustomScheduler("task3");
        System.out.println("Scheduling - "+new Date());
        var future= scheduledExecutorService.schedule(runnable,8,TimeUnit.SECONDS); // schedule at currentTime + 8 seconds
        System.out.println("Scheduling - "+new Date());
        var future1= scheduledExecutorService.schedule(runnable1,2,TimeUnit.SECONDS);
//        scheduledExecutorService.shutdown();
        System.out.println("Scheduling - "+new Date());
        var future2= scheduledExecutorService.schedule(runnable2,5,TimeUnit.SECONDS);
//        scheduledExecutorService.shutdown();
    }
}

@Data
@AllArgsConstructor
@NoArgsConstructor
class CustomScheduler implements Runnable{
    private String taskName;
    @Override
    public void run () {
        System.out.println("Scheduled task "+taskName+" at "+new Date());
    }

}