====== Apache Architecture ======
refer: http://stackoverflow.com/questions/17999140/prefork-vs-worker-module-for-apache-what-is-being-used\\
MPM(Multi Processing Module)
===== MPM Prefork Architecture =====
Basic configuration:
  * StartServers: number of server processes to start
  * MinSpareServers: minimum number of server processes which are kept spare
  * MaxSpareServers: maximum **number of server processes which are kept spare**
  * MaxClients:  maximum number of server processes allowed to start => Limist number of httpd created and processing the request. For example: MaxClients 10, And clients send **100 concurrency requests to server**, The server only **create max 10 server process httpd** for processing, and **99 remain requests will waiting in the queues**
{{:apache:preforkmodel.png|}}
Config example:<code>
<IfModule mpm_prefork_module>
    StartServers          6
    MinSpareServers       6
    MaxSpareServers      12
    MaxClients          12
    MaxRequestsPerChild   0
</IfModule></code>
check config:
  * check number of httpd process with none client request:<code bash>
ps -eaf | grep httpd
</code>output:<code>
root      1629     1  0 20:56 ?        00:00:00 /usr/local/apache/bin/httpd
apache    1631  1629  0 20:56 ?        00:00:00 /usr/local/apache/bin/httpd
apache    1632  1629  0 20:56 ?        00:00:00 /usr/local/apache/bin/httpd
apache    1633  1629  0 20:56 ?        00:00:00 /usr/local/apache/bin/httpd
apache    1634  1629  0 20:56 ?        00:00:00 /usr/local/apache/bin/httpd
apache    1635  1629  0 20:56 ?        00:00:00 /usr/local/apache/bin/httpd
apache    1636  1629  0 20:56 ?        00:00:00 /usr/local/apache/bin/httpd
</code> => 7 processes = MinSpareServers + 1
  * run load test with 20 concurrecy requests to server:<code bash>
ab -n 200 -c 20 http://shop.babies.vn/
</code> And check number of httpd processes:<code>
ps -eaf | grep httpd
root      1013     1  0 19:50 ?        00:00:00 /usr/local/apache/bin/httpd
apache    1144  1013  0 20:10 ?        00:00:09 /usr/local/apache/bin/httpd
apache    1210  1013  1 20:29 ?        00:00:05 /usr/local/apache/bin/httpd
apache    1216  1013  2 20:30 ?        00:00:05 /usr/local/apache/bin/httpd
apache    1219  1013  2 20:30 ?        00:00:06 /usr/local/apache/bin/httpd
apache    1220  1013  2 20:30 ?        00:00:05 /usr/local/apache/bin/httpd
apache    1226  1013  8 20:33 ?        00:00:06 /usr/local/apache/bin/httpd
apache    1227  1013  8 20:33 ?        00:00:06 /usr/local/apache/bin/httpd
apache    1228  1013  8 20:33 ?        00:00:06 /usr/local/apache/bin/httpd
apache    1229  1013  7 20:33 ?        00:00:05 /usr/local/apache/bin/httpd
apache    1230  1013  6 20:33 ?        00:00:04 /usr/local/apache/bin/httpd
apache    1231  1013  8 20:33 ?        00:00:05 /usr/local/apache/bin/httpd
apache    1288  1013  8 20:34 ?        00:00:03 /usr/local/apache/bin/httpd
</code> => max httpd processes = 13 = maxClients + 1
===== MPM worker Architecture =====
  * StartServers: initial number of server processes to start
  * MinSpareThreads: minimum number of worker threads which are kept spare
  * MaxSpareThreads: maximum number of worker threads which are kept spare
  * ThreadsPerChild: constant number of worker threads in each server process
{{:apache:apacheworker.png|}}
===== Debug architecture of apache =====
==== Get current MPM is running: MPM Prefork or MPM worker ====
<code bash>
apachectl -V
Server version: Apache/2.2.15 (Unix)
Server built:   Apr  3 2014 23:56:16
Server's Module Magic Number: 20051115:25
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"
...........................
</code>
==== compiled modules in MPM Prefork(httpd) and MPM worker(httpd.worker) ====
  * httpd -V<code>
Server version: Apache/2.2.15 (Unix)
Server built:   Apr  3 2014 23:56:16
Server's Module Magic Number: 20051115:25
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"
</code>
  * httpd.worker -V<code bash>
Server version: Apache/2.2.15 (Unix)
Server built:   Apr  3 2014 23:56:59
Server's Module Magic Number: 20051115:25
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"
</code>
  * Difference between "httpd -V" and "httpd.worker -V"
    * httpd -V<code>
Server MPM:     Prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APACHE_MPM_DIR="server/mpm/prefork"
    </code>
    * httpd.worker -V<code>
Server MPM:     Worker
  threaded:     yes (fixed thread count)
    forked:     yes (variable process count)
Server compiled with....
 -D APACHE_MPM_DIR="server/mpm/worker"
    </code>
  * httpd -l<code>
Compiled in modules:
  core.c
  prefork.c
  http_core.c
  mod_so.c
</code>
  * httpd.worker -l<code>
Compiled in modules:
  core.c
  worker.c
  http_core.c
  mod_so.c
</code>
==== Debug processes and used memory, cpu ====
  * netstat -anp | grep 80 | grep LISTEN<code>
tcp        0      0 :::80                       :::*                        LISTEN      5141/httpd
=> http listen on port 80 with PID(ProcessID) 5141
</code>
  * ps -eaf | grep 5141<code bash>
ps -eaf | grep 5141
UID        PID  PPID  C STIME TTY      TIME      CMD
root      5141     1  0 15:38 ?        00:00:00 /usr/sbin/httpd
apache    5176  5141  0 15:40 ?        00:00:01 /usr/sbin/httpd
apache    5196  5141  0 15:42 ?        00:00:02 /usr/sbin/httpd
apache    5353  5141  0 15:58 ?        00:00:00 /usr/sbin/httpd
apache    5358  5141  0 15:58 ?        00:00:00 /usr/sbin/httpd
apache    5360  5141  0 15:59 ?        00:00:00 /usr/sbin/httpd
</code>=> PPID(Parent PID). the master process is 5141, and sub processes are 5176, 5196, 5353, 5358, 5360 with CMD is /usr/sbin/httpd
  * ps -aux | grep /usr/sbin/httpd<code bash>
ps -aux | grep /usr/sbin/httpd
USER      PID  %CPU  %MEM  VSZ   RSS TTY  STAT START   TIME COMMAND
root      5141  0.0  1.9 254904  9920 ?   Ss   15:38   0:00 /usr/sbin/httpd
apache    5176  0.1  9.0 290320 45340 ?   S    15:40   0:01 /usr/sbin/httpd
apache    5196  0.1  9.3 291896 46956 ?   S    15:42   0:02 /usr/sbin/httpd
apache    5353  0.1  6.8 279708 34160 ?   S    15:58   0:00 /usr/sbin/httpd
apache    5358  0.0  3.3 263124 16592 ?   S    15:58   0:00 /usr/sbin/httpd
apache    5360  0.1  7.6 283964 38312 ?   S    15:59   0:00 /usr/sbin/httpd
</code>With VSZ is Virtual Memory Size(address space allocated) , and RSS is Resident Set Size (physically resident memory)
  * pmap -x 6726 | sort -nk +2<code bash>
pmap -x 6812 | sort -nk +2
00007fcacac95000    2048       0       0 -----  mod_mime_magic.so
00007fcacb4a8000    2048       0       0 -----  mod_log_config.so
00007fcacc0c1000    2048       0       0 -----  mod_authz_user.so
00007fcacccd7000    2048       0       0 -----  mod_auth_digest.so
00007fcacd559000    2048       0       0 -----  libdl-2.12.so
00007fcacdb06000    2048       0       0 -----  libpthread-2.12.so
00007fcace4db000    2048       0       0 -----  libcrypt-2.12.so
00007fcad1562000    2384    2356    2356 rw---    [ anon ]
00007fcac723b000    3268    1672       0 r-x--  libphp5.so
00007fcad17b6000   47848   47488   47488 rw---    [ anon ]
</code>
===== Optimize apache and PHP config =====
==== optimize load module apache ====
Config Optimize load modules for httpd with Explain directives with these modules:
<code bash>
LoadModule authz_host_module modules/mod_authz_host.so#Order
LoadModule access_compat_module modules/mod_access_compat.so#Require
LoadModule log_config_module modules/mod_log_config.so#LogFormat,TransferLog
LoadModule expires_module modules/mod_expires.so
LoadModule deflate_module modules/mod_deflate.so
LoadModule headers_module modules/mod_headers.so
LoadModule env_module modules/mod_env.so
LoadModule setenvif_module modules/mod_setenvif.so#BrowserMatch
LoadModule mime_module modules/mod_mime.so#AddHandler
LoadModule autoindex_module modules/mod_autoindex.so#IndexOptions
LoadModule negotiation_module modules/mod_negotiation.so#LanguagePriority
LoadModule dir_module modules/mod_dir.so#DirectoryIndex
LoadModule alias_module modules/mod_alias.so#Alias
LoadModule rewrite_module modules/mod_rewrite.so
</code>
==== optimize load module php ====
===== Custom Config for Apache =====
==== Config disable warning log from browser ====
With this config, the log will display in PHP error log but they don't display in browser side\\\
Update httpd.conf
<code php>
<IfModule mod_php5.c>
    php_admin_flag display_errors off
</IfModule>
</code>