Apache MPM Confusion -- Clarification Needed

Question

I'm working on the linux box where i didn't compile and build Apache. I can't tell which Apache MPM (prefork or worker) I'm using because there seems to be executables for both in /usr/sbin/. This is a CentOS box:

httpd
httpd.worker

In the script /usr/sbin/apachectl is the following line:

# the path to your httpd binary, including options if necessary
HTTPD='/usr/sbin/httpd'

However, /usr/sbin/apachectl also shows HTTPD configuration in the following file which makes me believe it's overriding the above options for HTTPD and pointing it at httpd.worker:

$ cat /etc/sysconfig/httpd
# Configuration file for the httpd service.

#
# The default processing model (MPM) is the process-based
# 'prefork' model.  A thread-based model, 'worker', is also
# available, but does not work with some modules (such as PHP).
# The service must be stopped before changing this variable.
#
HTTPD=/usr/sbin/httpd.worker

#
# To pass additional options (for instance, -D definitions) to the
# httpd binary at startup, set OPTIONS here.
#
#OPTIONS=

#
# By default, the httpd process is started in the C locale; to 
# change the locale in which the server runs, the HTTPD_LANG
# variable can be set.
#
#HTTPD_LANG=C

#
# By default, the httpd process will create the file
# /var/run/httpd/httpd.pid in which it records its process
# identification number when it starts.  If an alternate location is
# specified in httpd.conf (via the PidFile directive), the new
# location needs to be reported in the PIDFILE.
#
#PIDFILE=/var/run/httpd/httpd.pid

My conclusion is that i'm using MPM worker. However, why would i have an httpd executable in /usr/sbin that seems compiled as MPM prefork? Look at these commands? Artifacts maybe?:

# httpd -l
compiled in modules:
core.c
prefork.c
http_core.c
mod_so.c

$ httpd -V
Server version: Apache/2.2.15 (Unix)
Server built:   Feb 13 2012 22:31:42
Server's Module Magic Number: 20051115:24
Server loaded:  APR 1.3.9, APR-Util 1.3.9
Compiled using: APR 1.3.9, APR-Util 1.3.9
Architecture:   64-bit
Server MPM:     Prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APACHE_MPM_DIR="server/mpm/prefork"
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_SYSVSEM_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=128
 -D HTTPD_ROOT="/etc/httpd"
 -D SUEXEC_BIN="/usr/sbin/suexec"
 -D DEFAULT_PIDLOG="run/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_LOCKFILE="logs/accept.lock"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="conf/mime.types"
 -D SERVER_CONFIG_FILE="conf/httpd.conf"

$ httpd.worker -l
Compiled in modules:
core.c
worker.c
http_core.c
mod_so.c

$ apachectl -l
Compiled in modules:
core.c
worker.c
http_core.c
mod_so.c
# apachectl -V
Server version: Apache/2.2.15 (Unix)
Server built:   Feb 13 2012 22:33:00
Server's Module Magic Number: 20051115:24
Server loaded:  APR 1.3.9, APR-Util 1.3.9
Compiled using: APR 1.3.9, APR-Util 1.3.9
Architecture:   64-bit
Server MPM:     Worker
   threaded:     yes (fixed thread count)
   forked:     yes (variable process count)
Server compiled with....
-D APACHE_MPM_DIR="server/mpm/worker"
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_SYSVSEM_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=128
 -D HTTPD_ROOT="/etc/httpd"
 -D SUEXEC_BIN="/usr/sbin/suexec"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="conf/mime.types"
 -D SERVER_CONFIG_FILE="conf/httpd.conf"

the final reason I believe i'm running httpd.worker:

ps -C httpd.worker -F
UID        PID  PPID  C    SZ   RSS PSR STIME TTY          TIME CMD
root     13603     1  0 34690  4852   1 01:58 ?        00:00:00 /usr/sbin/httpd.worker
apache   13605 13603  0 34619  2352   1 01:58 ?        00:00:00 /usr/sbin/httpd.worker
apache   13606 13603  0 123554 7444   1 01:58 ?        00:00:00 /usr/sbin/httpd.worker
apache   13607 13603  0 240987 52604  0 01:58 ?        00:00:00 /usr/sbin/httpd.worker
apache   13609 13603  0 273755 52396  0 01:58 ?        00:00:00 /usr/sbin/httpd.worker
apache   13611 13603  0 290139 52128  0 01:58 ?        00:00:00 /usr/sbin/httpd.worker

shelika shelika · Accepted Answer · 2012-05-02T20:30:31

If you are on CentOS, open /usr/sbin/apachectl and below the following lines you mentioned

# the path to your httpd binary, including options if necessary 
HTTPD='/usr/sbin/httpd'

you will find the following lines:

# Source /etc/sysconfig/httpd for $HTTPD setting, etc.
if [ -r /etc/sysconfig/httpd ]; then
   . /etc/sysconfig/httpd
fi

That is how your apachectl is grabbing and overriding apachectl own HTTPD variable.

This also means that you are indeed using worker mpm instead of prefork.

Apache MPM Confusion -- Clarification Needed

1 Answers