우분투를 설치 하고 나서 apt-get 명령어를 이용하여 apache2를 설치 한 후, 명령어를 다음과 같이 apache2 에 옵션을 대문자 V로 하여 실행을 하면 현재 apache2가 서버의 MPM 실행모드가 어떤것인지 다음과 같이 확인 해 볼 수 있습니다.


-----------------------------------------------------------------------------------------------------
# apache2 -V
Server version: Apache/2.2.22 (Ubuntu)
Server built:   Jul 12 2013 13:44:46
Server's Module Magic Number: 20051115:30
Server loaded:  APR 1.4.6, APR-Util 1.3.12
Compiled using: APR 1.4.6, APR-Util 1.3.12
Architecture:   32-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/apache2"
 -D SUEXEC_BIN="/usr/lib/apache2/suexec"
 -D DEFAULT_PIDLOG="/var/run/apache2.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="mime.types"
 -D SERVER_CONFIG_FILE="apache2.conf"
-----------------------------------------------------------------------------------------------------
확인 해보면 Worker 모드로 동작 하는 것을 확인 해 볼 수 있습니다.

아래의 내용은 설정파일("/etc/apache2/apache2.conf" )의 전체 내용 입니다.

 

#
# Based upon the NCSA server configuration files originally by Rob McCool.
#
# This is the main Apache server configuration file.  It contains the
# configuration directives that give the server its instructions.
# See http://httpd.apache.org/docs/2.2/ for detailed information about
# the directives.
#
# Do NOT simply read the instructions in here without understanding
# what they do.  They're here only as hints or reminders.  If you are unsure
# consult the online docs. You have been warned.
#
# The configuration directives are grouped into three basic sections:
#  1. Directives that control the operation of the Apache server process as a
#     whole (the 'global environment').
#  2. Directives that define the parameters of the 'main' or 'default' server,
#     which responds to requests that aren't handled by a virtual host.
#     These directives also provide default values for the settings
#     of all virtual hosts.
#  3. Settings for virtual hosts, which allow Web requests to be sent to
#     different IP addresses or hostnames and have them handled by the
#     same Apache server process.
#
# Configuration and logfile names: If the filenames you specify for many
# of the server's control files begin with "/" (or "drive:/" for Win32), the
# server will use that explicit path.  If the filenames do *not* begin
# with "/", the value of ServerRoot is prepended -- so "foo.log"
# with ServerRoot set to "/etc/apache2" will be interpreted by the
# server as "/etc/apache2/foo.log".
#

### Section 1: Global Environment
#
# The directives in this section affect the overall operation of Apache,
# such as the number of concurrent requests it can handle or where it
# can find its configuration files.
#

#
# ServerRoot: The top of the directory tree under which the server's
# configuration, error, and log files are kept.
#
# NOTE!  If you intend to place this on an NFS (or otherwise network)
# mounted filesystem then please read the LockFile documentation (available
# at <URL:http://httpd.apache.org/docs/2.2/mod/mpm_common.html#lockfile>);
# you will save yourself a lot of trouble.
#
# Do NOT add a slash at the end of the directory path.
#
#ServerRoot "/etc/apache2"

#
# The accept serialization lock file MUST BE STORED ON A LOCAL DISK.
#
LockFile ${APACHE_LOCK_DIR}/accept.lock

#
# PidFile: The file in which the server should record its process
# identification number when it starts.
# This needs to be set in /etc/apache2/envvars
#
PidFile ${APACHE_PID_FILE}

#
# Timeout: The number of seconds before receives and sends time out.
#
Timeout 300

#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive On

#
# MaxKeepAliveRequests: The maximum number of requests to allow
# during a persistent connection. Set to 0 to allow an unlimited amount.
# We recommend you leave this number high, for maximum performance.
#
MaxKeepAliveRequests 100

#
# KeepAliveTimeout: Number of seconds to wait for the next request from the
# same client on the same connection.
#
KeepAliveTimeout 5

##
## Server-Pool Size Regulation (MPM specific)
##

# prefork MPM
# 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
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule mpm_prefork_module>
    StartServers          5
    MinSpareServers       5
    MaxSpareServers      10
    MaxClients          150
    MaxRequestsPerChild   0
</IfModule>

# worker MPM
# 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
# ThreadLimit: ThreadsPerChild can be changed to this maximum value during a
#              graceful restart. ThreadLimit can only be changed by stopping
#              and starting Apache.
# ThreadsPerChild: constant number of worker threads in each server process
# MaxClients: maximum number of simultaneous client connections
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule mpm_worker_module>
    StartServers          2
    MinSpareThreads      25
    MaxSpareThreads      75
    ThreadLimit          64
    ThreadsPerChild      25
    MaxClients          150
    MaxRequestsPerChild   0
</IfModule>

# event MPM
# 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
# MaxClients: maximum number of simultaneous client connections
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule mpm_event_module>
    StartServers          2
    MinSpareThreads      25
    MaxSpareThreads      75
    ThreadLimit          64
    ThreadsPerChild      25
    MaxClients          150
    MaxRequestsPerChild   0
</IfModule>

# These need to be set in /etc/apache2/envvars
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}

#
# AccessFileName: The name of the file to look for in each directory
# for additional configuration directives.  See also the AllowOverride
# directive.
#

AccessFileName .htaccess

#
# The following lines prevent .htaccess and .htpasswd files from being
# viewed by Web clients.
#
<Files ~ "^\.ht">
    Order allow,deny
    Deny from all
    Satisfy all
</Files>

#
# DefaultType is the default MIME type the server will use for a document
# if it cannot otherwise determine one, such as from filename extensions.
# If your server contains mostly text or HTML documents, "text/plain" is
# a good value.  If most of your content is binary, such as applications
# or images, you may want to use "application/octet-stream" instead to
# keep browsers from trying to display binary files as though they are
# text.
#
# It is also possible to omit any default MIME type and let the
# client's browser guess an appropriate action instead. Typically the
# browser will decide based on the file's extension then. In cases
# where no good assumption can be made, letting the default MIME type
# unset is suggested  instead of forcing the browser to accept
# incorrect  metadata.
#
DefaultType None


#
# HostnameLookups: Log the names of clients or just their IP addresses
# e.g., www.apache.org (on) or 204.62.129.132 (off).
# The default is off because it'd be overall better for the net if people
# had to knowingly turn this feature on, since enabling it means that
# each client request will result in AT LEAST one lookup request to the
# nameserver.
#
HostnameLookups Off

# ErrorLog: The location of the error log file.
# If you do not specify an ErrorLog directive within a <VirtualHost>
# container, error messages relating to that virtual host will be
# logged here.  If you *do* define an error logfile for a <VirtualHost>
# container, that host's errors will be logged there and not here.
#
ErrorLog ${APACHE_LOG_DIR}/error.log

#
# LogLevel: Control the number of messages logged to the error_log.
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
#
LogLevel warn

# Include module configuration:
Include mods-enabled/*.load
Include mods-enabled/*.conf

# Include all the user configurations:
Include httpd.conf

# Include ports listing
Include ports.conf

#
# The following directives define some format nicknames for use with
# a CustomLog directive (see below).
# If you are behind a reverse proxy, you might want to change %h into %{X-Forwarded-For}i
#
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent

# Include of directories ignores editors' and dpkg's backup files,
# see README.Debian for details.

# Include generic snippets of statements
Include conf.d/

# Include the virtual host configurations:
Include sites-enabled/

 

 

apache2는 다중처리모듈 (MPMs)이라는 교체할 수 있는 동기화 모델을 지원 합니다. 

만일 아파치를 손수 컴파일 해서 사용 할 경우에는 MPM 방식을 결정해서 컴파일 합니다.
 
apache2 웹서버의 속도 및 확장성은 어떠한 MPM을 선택 하였는가에 따라 그 성능이 좌우 될 수 있습니다.

 * Prefork MPM
쓰레드가 한개인 자식 프로세스를 여러개 사용하며, 각 프로세스는 한번에 한 연결 만을 담당 하게 됩니다.
이 모드는 프로세스간에 메모리를 직접 공유하지 않으므로, 메모리 공간이 독립적이므로, 안정적으로 운영 할 수 있습니다. 

 * Worker MPM
여러 자식 프로세스가 각각 여러 쓰레드를 사용하며, 각 쓰레드는 한번에 한 연결 만을 담당 합니다. 
하지만 메모리 공간 전체를 복수의 쓰레드가 공유 하여 사용 하게 됨으로써 리소스 경합이 발생하지 않도록 주의 해야 합니다. 


StartServers
아파시 시작시에 생성되는 자식 프로세스의 설정값으로 초기에 4개의 프로세스정도면 적당하며,접속이 많아질경우 동적으로 제어되어 프로세스의 개수를 늘립니다. (ThreadsPerChild 에 연관)

MaxClients
동시에 접속하여 처리될수 있는 client 최대 설정값 하나의 프로세스내에 복수의 쓰레드를 생성하고, 쓰레드 하나로 하나의 Client 를 처리합니다.

MinSpareThreads
MaxSpareThreads
프로세스당 쓰레드 생성의 최소에서 최대치 사이 값을 설정하며, MinSpareThreads를 ThreadsPerChild와 동일하게 맞추어 줍니다.

ThreadsPerChild
각각의 자식 프로세스의 쓰레드 생성 개수를 설정 합니다.

MaxRequestsPerChild
각각의 자식 프로세스가 처리할 요청수의 제한하며, 설정치 만큼 처리가 되면 해당 자식 프로세스는 종료되며 다시 생성하게 됩니다. 만일 이 값이 0 이면 무한대를 의미하며, 리소스를 생각할때 무한대로 설정하는것은 무의미 합니다.