Symptoms
Various issues related to Apache and Horde web interface may be observed, e.g.- "Login failed" message or a blank page in Horde web interface;
- Unable to send emails from Horde Webmail;
- web sites not opening properly.
Cause
If you try to host more than 300 websites on the server, Apache may fail to work because of a problem involving the file descriptors limit. Apache, by default, can handle only 1024 file descriptors. Every Virtual Host requires 2 or 4 (if HTTPS is enabled) log files, so with this scheme, only about 300 domains can be hosted without Apache recompilation. See: 260.Diagnostics
Run the following command to see the root of Apache processes tree:# ps axf | grep httpd | grep -v grep
2718 ? Ss 0:00 /usr/sbin/httpd
2720 ? S 0:00 \_ /usr/sbin/httpd
2721 ? S 0:03 \_ /usr/sbin/httpd
…
3821 ? S 0:00 \_ /usr/sbin/httpd
3901 ? S 0:00 \_ /usr/sbin/httpdAnd then check the number of open file descriptors in that process information:
# ls /proc/2718/fd/ | wc -l
1406If the returned value is more than 1024, it means that Apache does not have enough file descriptors and may fail to work properly.
Resolution
The Piped Logs feature that was implemented in Parallels Plesk Panel 8.2 allows you to host up to 900 domains, safely, on the default Apache web server. If you have more that 900 domains, you will still have to recompile Apache and certain other system packages as described in article 260. To enable Piped Logs, do the following:1. Log in to the server shell.
2. Issue this command:
# mysql -uadmin -p`cat /etc/psa/.psa.shadow` psa -e "replace into misc (param,val) values ('apache_pipelog', 'true');"3. Rebuild Apache configuration:
# $PRODUCT_ROOT_D/admin/sbin/websrvmng -v -a