Re: How to avoid running out of OS thread handles when spawning lots of short-lived threads?

[Steven Schveighoffer]

On Thu, 09 Jun 2011 19:17:28 -0400, David Nadlinger <s...@klickverbot.at>  
wrote:

The title says it all – how can I avoid running out of OS thread handles  
when spawning lots of short-lived threads?

In reality, I encountered the issue while writing tests a piece of code  
which spawns a thread, but this is the basic issue:

---
import core.thread;

void doNothing() {}
void main() {
   foreach (i; 0 .. 100_000) {
     auto t = new Thread(&doNothing);
     t.start();

     // Just to make sure the thread has time to terminate.
     Thread.sleep(dur!"msecs"(1));
   }
}
---

Even though the threads immediately terminate, the D Thread objects stay  
around a lot longer (until the garbage collector decides to collect  
them), and as pthread_detach is only called the Thread destructor, this  
causes the application to eventually fail with

core.thread.ThreadException@src/core/thread.d(812): Error creating thread

because the available OS thread handles are exhausted.

Any ideas how to properly fix that?

t.join() ?

http://www.digitalmars.com/d/2.0/phobos/core_thread.html#join

AFAIK, a thread cannot go away until you join it, because it still has to  
give you its exit status.

See this man page:  
http://pubs.opengroup.org/onlinepubs/007908799/xsh/pthread_join.html

It is unspecified whether a thread that has exited but remains unjoined  
counts against _POSIX_THREAD_THREADS_MAX.

-Steve