I'm writing a Perl program to run on Windows platforms (Win2K and
WinXP). whose job is to manage concurrent downloads using libwww-perl
(LWP). The basic model is that a manager process checks continuously
against a task list (actually a directory containing task files) and
launches a sub-process or thread to handle each download. Because the
downloads are expected to run concurrently, the manager doesn't wait
for the sub-processes to complete.
My first attempt used fork() to launch the sub-processes, and each
sub-process would then call exit(0) when complete. However, it
appears that exit(0) doesn't release the thread handles: the manager
would fork 64 sub-processes successfully, and then die with 'resource
temporarily unavailable' on the 65th. Note that this wasn't a case of
too many concurrent processes: most of the sub-processes would
already have exited, so there were never more than about 20 processes
active simultaneously.
I then rewrote the code using threads instead. Each thread was
created with new() and then immediately detached using detach(). The
manager doesn't need to get a result back from the thread.
This performed even worse: after a random number of thread creations
- between about 40 and 60 - Perl would simply exit, and Windows would
dump an exception log that indicated thread-related problems. Again,
the figure of 40-60 refers not to concurrent threads, but to total
threads created.
Has anyone had any experience in writing multi-threaded processes on
Windows using libwww-perl? Is it possible to do this stably, or is
multi-threading in Windows Perl not yet mature enough? Or,
alternatively, am I making some fundamental error in the way I'm
going about this?
Thanks in advance for any suggestions,
Angus
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