WorkManager and a high workload

Question

I'm working on an application which interacts with hundreds of devices across a network. The type of work being committed requires a lot of the concurrent threads (mostly because each of them requires network interaction and does so separately, but for other reasons as well). At the moment, we're in the area of requiring about 20-30 threads per device being interacted with.

A simple calculation puts this at thousands of threads, even up to 10,000 threads. If we put aside the CPU penalty for thread-switching, etc., how many threads can Java 5 running on CentOS 64-bit handle? Is this just a matter of RAM or is there anything else we should consider?

Thanks!

Answer 1

I think up to 65k threads is OK with java, the only thing you need to consider is stack space - linux by default allocates 48k per thread/process as stack space, which is wasteful for java (which doesn't have stack-allocated objects, hence uses much less stack space). This will easily use 500 megs for 10k threads.

Answer 2

In such situation its always recomended to use Thread Pooling.

Thread pools address two different problems: they usually provide improved performance when executing large numbers of asynchronous tasks, due to reduced per-task invocation overhead, and they provide a means of bounding and managing the resources, including threads, consumed when executing a collection of tasks. Each ThreadPoolExecutor also maintains some basic statistics, such as the number of completed tasks.

ThreadPoolExecutor is class you should be using.

http://www.javamex.com/tutorials/threads/ThreadPoolExecutor.shtml

Answer 3

If this is really an absolute requirement, you might wan't to have a look at a language that's specifically build to deal with this level of concurrent threads, such as erlang.

Answer 4

Like others are suggesting, you should use NIO. We had an app that used a lot (but much less than you are planning) of threads (e.g. 1,000 ) and it was already very inefficient. If you have to use THAT much threads, it's definitely time to consider the use of NIO.

For network, if your apps are using HTTP, one very easy tool would be Async-HTTP-client by 2 very famous author in this field.

If you use a different protocol, using the underlying implementation of Async-HTTP-client (netty) would be recommendable.