Java执行程序服务连接池

Question

I am attempting to use connection pooling for Executor Service.

I am facing some problem when connection pool config is initialSize=3, maxToal=5, maxIdle=5.

I need to process 10 services at a time for every minute. But its picking only 5 services for every minute.

If i configure initialSize=3, maxToal=10, maxIdle=10 then its picking 10 services for every minute..

I am new to multithreading and connection. Below is my code snippet. Please provide suggestion.

public class TestScheduledExecutorService {
    public static void main (String a[]) {
        ScheduledExecutorService service = null;
        try {
            TestObject runnableBatch = new TestObject() {
                public void run() {
                    testMethod ();
                }
            };
            service = Executors.newSingleThreadScheduledExecutor();
            service.scheduleAtFixedRate(runnableBatch, 0, 30, TimeUnit.SECONDS);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public class TestObject implements Runnable{

    public void testMethod (int inc) {
        ExecutorService service = null;
        try {
            service = Executors.newFixedThreadPool(10);
            for (int i = 0; i < 10; i++) {
                service.submit(new TestService());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
    }
}

public class TestService implements Callable{

    Connection conn = null;

    public void process(Connection conn) {
        try {
            if (conn != null) {
                System.out.println("Thread & Connection pool conn : "+Thread.currentThread() + " :: " +conn);
                // service process here
            } else {
                System.out.println("Connection pool conn is null : ");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
        }
    }

    @Override
    public Object call() throws Exception {
        ConnectionPoolTest cp = ConnectionPoolTest.getInstance();
        BasicDataSource bds = cp.getBasicDataSource();
        conn = bds.getConnection();
        System.out.println(" call() "); **// it prints only 5 times for every minute eventhough total services are 10**
        process(conn);
        return null;
    }

}

public class ConnectionPoolTest {

private static ConnectionPoolTest dataSource = new ConnectionPoolTest();

    private static BasicDataSource basicDataSource = null;

    private ConnectionPoolTest() {  
    }

    public static ConnectionPoolTest getInstance() { 
        if (dataSource == null) 
            dataSource = new ConnectionPoolTest();
        return dataSource;
    }

    public BasicDataSource getBasicDataSource() throws Exception {
        try {
            basicDataSource = new BasicDataSource();

            basicDataSource.setInitialSize(3);
            basicDataSource.setMaxTotal(10);
            basicDataSource.setMaxIdle(10);
        } catch (Exception e) {
            throw e;
        }
        return basicDataSource;
    }

}

Answer 1

For Executor Service

 initialSize : Specified Number of Threads to spin , when New executor is created.
 maxTotal    : Number of Threads that can exist at max peak load.
 maxIdle     : Number of Thread that are kept active even if load goes below threshold.

As you mentioned, you want to pick up 10 number of tasks in parallel, we should have maxTotal set at 10. intialSize can be configured to a number that you think is optimal at the start , lets say 3 - 5. maxIdle is the number of threads you want to keep active , we generally assume how many threads are required if tasks are submitted. though there is no standard recomendation, vaues might be determined a number of various factors like .

1. Distribution of task submitted during the minute
2. Duration of Task
3. Urgency of executing those tasks in parallel.

As you mentioned you need 10 parallel tasks, then you will have to configure 10 as maxTotal, considering your task distribution and Duration causes overlap. If duration is pretty small , and distribution is even you can also survive with a lower number too.