perl cgi threads

I am having bit of a problem with my cgi web application, I use ithreads to do some parallel processing, where all the thread have a common 'goal'. Thus I detach all of them, and once I find my answer, I call exit. However the problem is that the script will actually continue processing even after the user has closed the connection and left, which of cour开发者_如何学Cse if a problem resourcewise. Is there any way to force exit on the parent process if the user has disconnected?

If you're running under Apache, if the client closes the connection prematurely, it sends a SIGTERM to the cgi process. In my simple testing, that kills the script and threads as default behavior.

However, if there is a proxy between the server and the client, it's possible that Apache will not be able to detect the closed connection (as the connection from the server to the proxy may remain open) - in that case, you're out of luck.

AFAIK create and destroy threads isn't (at least for now) a good Perl practice because it will constantly increase the memory usage!
You should think in some other way to get the job done. Usually the solution is create a pool of threads and send arguments with the help of a shared array or Thread::Queue.

I personally would suggest changing you approach and, when creating these threads for the client connection, would be to save and associate PID of each thread with the client connection. I personally like to use daemons instead of threads, ie. Proc::Daemon. When client disconnects prematurely (before the threads finish), send SIGTERM to each process ID associated with that client.

To exit gracefully, override the termination sub in the thread process with a stop condition, so something like:

$SIG{TERM} = sub { $continue = 0; };

Where $continue would be the condition of the thread processing loop. You still would have to watch out for code errors, because even you can try overriding $SIG{__DIE__}, the die() method usually doesn't respect that and dies instantly without grace ;) (at least from my experience)

I'm not sure how you go about detecting if the user has disconnected, but, if they have, you'll have to make the threads stop yourself, since they're obviously not being killed automatically.

Destroying threads is a dangerous operation, so there isn't a good way to do it.

The standard way, as far as I know, is to have a shared variable that the threads check periodically to determine if they should keep working. Set it to some value before you exit, and check for that value inside your threads.

You can also send a signal to the threads to kill them. The docs know more about this than I do.