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.

• user93353: Couple of things - Is NIO really faster - mailinator.blogspot.in/2008/02/…. Also, won't using a thread pool be advantageous in terms of the cost of creating a new thread - i.e. each thread runs for a very short time in my case. So may be cost of creating the thread is high as compared to the length of time the thread runs.
• David Harkness: The OP was concerned about creating a new thread for each request--not about using too many concurrent threads. A thread pool alleviates this problem. NIO would be helpful if the volume of requests is consuming too many resources.