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From Manuel Vacelet <manuel.vace...@gmail.com>
Subject [users@httpd] mod_ldap cache and strace doesn't tell the same story
Date Tue, 16 Mar 2010 10:06:42 GMT
Hi all,

I'm facing a strange issue.
I have a major performance penalty on some apache related operations
(svn checkout that used to take 5mn but that suddenly takes more than
7 hours).

I'm running a standard RHEL5.3 with apache 2.2.3 (fyi the server runs
mod_php, mod_auth_mysql and some other modules too).

Thanks to strace, I identified that the httpd process that is "very
long" (the httpd process that discuss with svn client that takes hour
to complete).
The process makes a lot of operation on a file descriptor attached to
my ldap server and is regulary blocking with following syscall:
poll([{fd=3, events=POLLIN|POLLPRI|POLLERR|POLLHUP}], 1, -1 <unfinished ...>

fd3 is a socket (/proc/<pid>/fd/3) and the inode of this socket is
used to communicate with the ldap server (shown by netstat)

This is where I no longer understand what happens:
- I'm using mod_ldap so there should be a cache of all ldap info.
- ldap-status confirm that the credentials used for the svn operation
are in cache.
- The cache is far from full (2%)
- The hit ratio is close to 100%

=> Why there is an activity between my httpd process and the ldap server ?

Any help appreciate,
Cheers,
Manuel

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