Moving from normal threads to ExecutorService thread pools in java

Question

I had my original threading code which worked well, but since my tasks were shortlived, I decided to use thread pools through ExecutorService.

This was my original code

public class MyRun implements Runnable
{
    private Socket socket = null;
    public MyRun(Socket s)
    {
        socket = s;
        thread = new Thread(this, "SocketThread");
        thread.start();
    }
    public void run()
    {
        // My actual thread code
    }
}

My main program

...
ss = new ServerSocket(port);
....
MyRun st = null;
while (!stop)
{
    st = new MyRun(ss.accept());
    st = null;
}

New code

public MyRun(Socket s)
{
    socket = s;
    thread = new Thread(this, "SocketThread");
}

run() left unchanged

Changed Main program

private static ExecutorService execService = Executors.newCachedThreadPool();
....
....
while (!stop)
{
    execService.execute(new MyRun(ss.accept()));
}

Changed code seems to be working fine, but I just want to make sure there is nothing I am missing. I want all threads to execute simultaneously.

Answer 1

A few simple remarks :

• thread = new Thread(this, "SocketThread"); is no longer needed in MyRun, since the ExecutorService is the one creating and managing the Threads.
• you will want to call execService.shutDown() to properly clean up the resources of the executorService.

Answer 2

As I understand, you're still using blocking I/O. So each connection still consumes the whole thread, and there is little difference whether this thread was created manually or taken from a pool.

To employ thread pool efficiently, you have to use non-blocking I/O (NIO), but it is harder to use.

So the question is, have you enough memory to spend a thread per connection? If yes, continue to use your old code, executor service wouldn't help you. If no, take a NIO library (Netty is most widely known, df4j - almost unknown), and follow its suggestion how to use executor service.