Accpet() need more file descriptor

Question

my application server is using multithread to deal with high concurrency socket requests. When accpet() a request, it assign a FD, create a thread to deal, the thread will close the FD after finish the processing and thread_exit.
my question is: when there are threads concurrency dealing 56~57 FDs, accept() can't get a new FD (errno.24). I know FD is limited in one process, I can try to fork sub_process to reach the high concurrency.
But I wonder isn't there any other good method to solve the problem? How can a Web server reach a high concurrency?
Any suggest is appreciated!
Jenny

Answer 1

Hi Jenny,<BR><BR>
First of all, you did not say which release of Solaris you are using,<BR>but I'll assume you are on a version later than 2.4.<BR>
You are correct when you say that the number of file descriptors <BR>
that can be opened is a per-process limit. Depending on the OS <BR>version the default value for this limit changes, but there <BR>are simple ways to increase it.<BR>
First of all there are two types of limits: a hard (system-wide) <BR>
limit and a soft limit. The hard limit can only be changed by root<BR>
but the soft limit can be changed by any user. There is one restriction<BR> on soft limits, they can never be set higher then the<BR>corresponding hard limit.<BR>
1. Use the command ulimit(1) from your shell to increase the soft<BR>
limit from its default value (64 before Solaris 8) to a specified <BR>value less than the hard limit.<BR>
2. Use the setrlimit(2) call to change both the soft and hard limits.<BR> You must be root to change the hard limit though.<BR>
3. Modify the /etc/system file and include the following line in <BR>
to increase the hard limit to 128:<BR><BR>
<CODE>set rlim_fd_cur=0x80</CODE><BR><BR>
After changing the /etc/system file, the system should be rebooted <BR>so that the change takes effect.<BR><BR>
Note that stdio routines are limited to using file descriptors <BR>
0 through 255. Even though the limit can be set higher than 256, if<BR>the fopen function cannot get a file descriptor lower than 256,<BR>then it will fail. This can be a problem if other routines <BR>use the open function directly. For example, if 256 files are<BR>
opened with the open function and none of them are closed, no other<BR>files can be opened with the fopen function because all of<BR>the low-numbered file descriptors have been used.<BR>
Also, note that it is somewhat dangerous to set the fd limits higher<BR>than 1024. There are some structures, such as fd_set in<BR> <sys/select.h>, defined in the system that assume the maximum fd is<BR>1023. If a program uses an fd larger than 1023 with the macros<BR>and routines that access such a structure, the program will<BR>corrupt its memory space because it will modify memory outside<BR>of the bounds of the structure.<BR><BR>
Caryl<BR>
Sun Developer Technical Support<BR>