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

Answer 1

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.