I wrote concurrent application and have caught the error:
buildFdSets: file descriptor out of range
I found out that it is the OS limit on the number of file descriptors in one process, in my FreeBSD it is 1024. It is the limit of select(). Also I have learned that there is another approach: kqueue().
My questions are:
kqueue() instead of select() in haskell programs?
I believe that GHC 7 now has support for using kqueue() in it's back end:
link to paper, descriptive blog post
However the Haskell Platform is not yet out for GHC 7.
You can simply upgrade to GHC 7, which is part of the Haskell Platform, which includes:
On POSIX platforms, there is a new I/O manager based on epoll/kqueue/poll, which allows multithreaded I/O code to scale to a much larger number (100k+) of threads
In particular:
Architecturally, our new I/O manager consists of two components. Our event notification library provides a clean and portable API, and abstracts the system-level mechanisms used to provide efficient event notifications (kqueue, epoll, and poll). We have also written a shim that implements the semi-public threadWaitRead and threadWaitWrite interfaces. This means that neither the core file or networking libraries, nor other low-level I/O libraries, require any changes to work with—and transparently benefit from the performance improvements of—our new code.
That is, just upgrade, and things work magically better.
Here's some reading material:
