I‘m getting an error which read as follows under FreeBSD 7.2 server and Squid stable caching server:

WARNING! Your cache is running out of filedescriptors

How do I fix this problem and increase the number of system-wide available filedescriptors for FreeBSD server?

For busy proxy caching server, you need to to increase the number of system-wide available filedescriptors, by editing /etc/sysctl.conf file. There is no need to make changes to squid.conf.

Find Current Squid File Descriptors Limits Under FreeBSD

Type the following command:
# squidclient mgr:info | grep 'file descri'
OR
# squidclient -p 8080 -u USERNAME -w 'secretePassword' mgr:info | grep 'file descri'

Increase Squid File Descriptors Limits

Type the following command at a shell prompt:
# sysctl kern.maxfilesperproc=8192
# sysctl kern.maxfiles=65535
To keep settings after reboot add them to /etc/sysctl.conf
echo 'kern.maxfilesperproc=8192' >> /etc/sysctl.conf
echo 'kern.maxfiles=65535' /etc/sysctl.conf
Where,

1. kern.maxfilesperproc – Set maximum number of open files to 65535
2. kern.maxfiles – Set maximum files allowed open per process to 8192

Optionally you may also want to increase port ranges:
# sysctl net.inet.ip.portrange.last=65535
# sysctl net.inet.ip.portrange.first=1024

Finally restart the squid and verify you got new FD settings for squid proxy server:
# squidclient mgr:info | grep 'file descri'

See also:

1. Squid Proxy WARNING! Your cache is running out of filedescriptors error and solution under Linux operating system