Apache httpd instability?

[Georgios Petasis]

Hi all,

Every a few minutes or so, I see logs similar to the following one, in 
apache's httpd error log:

[Wed Mar 13 15:06:01.223104 2013] [mpm_prefork:notice] [pid 3850] 
AH00170: caught SIGWINCH, shutting down gracefully
[Wed Mar 13 15:06:01.747820 2013] [core:notice] [pid 4002] SELinux 
policy enabled; httpd running as context system_u:system_r:httpd_t:s0
[Wed Mar 13 15:06:01.749783 2013] [suexec:notice] [pid 4002] AH01232: 
suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Wed Mar 13 15:06:02.000501 2013] [ssl:notice] [pid 4002] AH01886: SSL 
FIPS mode disabled
[Wed Mar 13 15:06:02.175544 2013] [auth_digest:notice] [pid 4002] 
AH01757: generating secret for digest authentication ...
[Wed Mar 13 15:06:03.000961 2013] [lbmethod_heartbeat:notice] [pid 4002] 
AH02282: No slotmem from mod_heartmonitor
[Wed Mar 13 15:06:03.001154 2013] [ssl:notice] [pid 4002] AH01886: SSL 
FIPS mode disabled
PHP Warning:  Module 'zip' already loaded in Unknown on line 0
[Wed Mar 13 15:06:03.194039 2013] [mpm_prefork:notice] [pid 4002] 
AH00163: Apache/2.4.3 (Fedora) OpenSSL/1.0.1e-fips PHP/5.4.12 
Rivet/2.1.0 configured -- resuming normal operations
[Wed Mar 13 15:06:03.194063 2013] [core:notice] [pid 4002] AH00094: 
Command line: '/usr/sbin/httpd -D FOREGROUND'

Something is causing these "restarts". How can I debug this?

George