Java：在这种情况下我应该使用多线程吗？

Question

I am writing a server side application using Java.

The server holds a number of users of the system. For each user, I want to synchronize its disk space with a remote network storage. Because synchronizations are independent, I am thinking to do them concurrently.

I am thinking to create one thread for each user and let the synchronization tasks to fire at the same time.

But the system can have tens of thousands of users. This means creating tens of thousand thread at one time and fire at the same time. I am not sure if this is something JVM can handle.

Even if it can handle this, will that be memory efficient because each thread have its own stack and this could be a big memory hit!

Please let me know your opinion.

Many thanks.

Answer 1

You could look at a fixed size thread pool giving a pool of threads to execute your task. This would give the benefit of multithreading with a sensible limit.

Check out Executors.newFixedThreadPool()

Answer 2

You should look into Non-blocking IO.

Here is a "random" article about it from courtesy of google: http://www.developer.com/java/article.php/3837316/Non-Blocking-IO-Made-Possible-in-Java.htm

Answer 3

Personally I wouldn't have tens of thousands of users on a single machine. You won't be able to much per user with this many users active. You should be able to afford more than one machine.

You can have this many thread in Java but as you say this is not efficient. You can use an NIO library to manage multiple connection with each thread.

Libraries like

http://mina.apache.org/

http://www.jboss.org/netty

Are suitable.

Also interesting http://code.google.com/p/nfs-rpc/