Apache负载均衡请求至Tomcat及DeltaManager的使用
一、系统环境
CentOS6.4X64最小化安装
二、环境准备
1.实验拓扑
2.同步各节点时间
apache，tomcat1,tomcat2的操作都是一样的
[root@apache ~]# yum install ntp -y [root@apache ~]# ntpdate asia.pool.ntp.org [root@apache ~]# hwclock -w [root@apache ~]# echo "*/10 * * * * /usr/sbin/ntpdate asia.pool.ntp.org &>/dev/null" >/var/spool/cron/root
3.安装jdk，tomcat1和tomcat2的安装过程一样，这里只给出tomcat1的安装过程
[root@tomcat1 ~]# tar xf jdk-8u45-linux-x64.tar.gz -C /usr/local/ #编辑环境变量配置文件 [root@tomcat1 ~]# cat /etc/profile.d/java.sh JAVA_HOME=/usr/local/jdk1.8.0_45 JAVA_BIN=$JAVA_HOME/bin JRE_HOME=$JAVA_HOME/jre PATH=$PATH:$JAVA_HOME/bin:$JAVA_HOME/jre/bin CLASSPATH=$JAVA_HOME/jre/lib:$JAVA_HOME/lib:$JAVA_HOME/jre/lib/charsets.jar #让环境变量生效 [root@tomcat1 ~]# source /etc/profile.d/java.sh #测试结果 [root@tomcat1 ~]# java -version java version "1.8.0_45" Java(TM) SE Runtime Environment (build 1.8.0_45-b14) Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)
4.安装tomcat，安装过程tomcat1和tomcat2一样
#下载软件 [root@tomcat1 ~]# wget http://apache.fayea.com/tomcat/tomcat-7/v7.0.62/bin/apache-tomcat-7.0.62.tar.gz [root@tomcat1 ~]# tar xf apache-tomcat-7.0.62.tar.gz -C /usr/local/ [root@tomcat1 ~]# ln -s /usr/local/apache-tomcat-7.0.62/ /usr/local/tomcat [root@tomcat1 ~]# cp /usr/local/tomcat/bin/catalina.sh /etc/init.d/tomcat #编辑启动脚本在第二行添加如下内容 [root@tomcat1 ~]# vim /etc/init.d/tomcat # chkconfig: 2345 63 37 # description: tomcat server init script # Source Function Library . /etc/init.d/functions JAVA_HOME=/usr/local/jdk1.8.0_45 CATALINA_HOME=/usr/local/tomcat #赋予脚本执行权限，并添加到开机自启动 [root@tomcat1 ~]# chmod 755 /etc/init.d/tomcat [root@tomcat1 ~]# chkconfig --add tomcat [root@tomcat1 ~]# chkconfig tomcat on #启动tomcat [root@tomcat1 ~]# service tomcat start Using CATALINA_BASE: /usr/local/tomcat Using CATALINA_HOME: /usr/local/tomcat Using CATALINA_TMPDIR: /usr/local/tomcat/temp Using JRE_HOME: /usr/local/jdk1.8.0_45 Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar Tomcat started. [root@tomcat1 ~]# netstat -anpt |grep java tcp 0 0 :::8080 :::* LISTEN 1583/java tcp 0 0 ::ffff:127.0.0.1:8005 :::* LISTEN 1583/java tcp 0 0 :::8009 :::* LISTEN 1583/java [root@tomcat1 ~]# service iptables stop
测试访问结果，访问地址http://192.168.3.74:8080和http://192.168.3.75:8080
到此tomcat安装成功
5.修改配置文件
tomcat1:
[root@tomcat1 ~]# vim /usr/local/tomcat/conf/server.xml
<Connector port="80" protocol="HTTP/1.1" #将端口修改成80
connectionTimeout="20000"
redirectPort="8443" />
<Engine name="Catalina" defaultHost="localhost" jvmRoute="TomcatA"> #增加jvmRoute
#增加一个虚拟主机
<Host name="www.test.com" appBase="/web"
unpackWARs="true" autoDeploy="true">
<Context path="/" docBase="webapp" reloadable="true"/>
</Host>
#增加虚拟主机的目录和测试文件
[root@tomcat1 ~]# mkdir -p /web/webapp
[root@tomcat1 ~]# vim /web/webapp/index.jsp
[root@tomcat1 ~]# cat /web/webapp/index.jsp
<%@ page language="java" %>
<html>
<head><title>TomcatA</title></head>
<body>
<h1><font color="blue">TomcatA </h1>
<table align="centre" border="1">
<tr>
<td>Session ID</td>
<% session.setAttribute("abc","abc"); %>
<td><%= session.getId() %></td>
</tr>
<tr>
<td>Created on</td>
<td><%= session.getCreationTime() %></td>
</tr>
</table>
</body>
</html>
#检查配置文件并重新启动tomcat
[root@tomcat1 ~]# service tomcat stop
Using CATALINA_BASE: /usr/local/tomcat
Using CATALINA_HOME: /usr/local/tomcat
Using CATALINA_TMPDIR: /usr/local/tomcat/temp
Using JRE_HOME: /usr/local/jdk1.8.0_45
Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
[root@tomcat1 ~]# service tomcat configtest #该命令只能在tomcat停止的时候执行，否则会报错
Using CATALINA_BASE: /usr/local/tomcat
Using CATALINA_HOME: /usr/local/tomcat
Using CATALINA_TMPDIR: /usr/local/tomcat/temp
Using JRE_HOME: /usr/local/jdk1.8.0_45
Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
Jun 19, 2015 10:58:16 AM org.apache.catalina.core.StandardContext setPath
WARNING: A context path must either be an empty string or start with a '/' and do not end with a '/'. The path [/] does not meet these criteria and has been changed to []
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server version: Apache Tomcat/7.0.62
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server built: May 7 2015 17:14:55 UTC
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server number: 7.0.62.0
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Name: Linux
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Version: 2.6.32-358.el6.x86_64
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Architecture: amd64
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Java Home: /usr/local/jdk1.8.0_45/jre
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Version: 1.8.0_45-b14
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Vendor: Oracle Corporation
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_BASE: /usr/local/tomcat
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_HOME: /usr/local/tomcat
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.endorsed.dirs=/usr/local/tomcat/endorsed
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.base=/usr/local/tomcat
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.home=/usr/local/tomcat
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.io.tmpdir=/usr/local/tomcat/temp
Jun 19, 2015 10:58:16 AM org.apache.catalina.core.AprLifecycleListener lifecycleEvent
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
Jun 19, 2015 10:58:16 AM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-bio-80"]
Jun 19, 2015 10:58:16 AM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-bio-8009"]
Jun 19, 2015 10:58:16 AM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1097 ms
#重新启动tomcat
[root@tomcat1 ~]# service tomcat start
Using CATALINA_BASE: /usr/local/tomcat
Using CATALINA_HOME: /usr/local/tomcat
Using CATALINA_TMPDIR: /usr/local/tomcat/temp
Using JRE_HOME: /usr/local/jdk1.8.0_45
Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
Tomcat started.
[root@tomcat1 ~]# netstat -tunlp |grep java
tcp 0 0 :::80 :::* LISTEN 1757/java
tcp 0 0 ::ffff:127.0.0.1:8005 :::* LISTEN 1757/java
tcp 0 0 :::8009 :::* LISTEN 1757/java
测试tomcat1的服务,需要在windows是做本地hosts解析，即192.168.3.74 www.test.com
tomcat2:
[root@tomcat2 ~]# vim /usr/local/tomcat/conf/server.xml
<Connector port="80" protocol="HTTP/1.1" #修改端口为80
connectionTimeout="20000"
redirectPort="8443" />
<Engine name="Catalina" defaultHost="localhost" jvmRoute="TomcatB"> #增加jvmRoute
<Host name="www.test.com" appBase="/web" #增加一个虚拟主机
unpackWARs="true" autoDeploy="ture">
<Context path="/" docBase="webapp" reloadable="true"/>
</Host>
#增加虚拟主机的目录和测试文件
[root@tomcat2 ~]# mkdir -p /web/webapp
[root@tomcat2 ~]# vim /web/webapp/index.jsp
[root@tomcat2 ~]# cat /web/webapp/index.jsp
<%@ page language="java" %>
<html>
<head><title>TomcatB</title></head>
<body>
<h1><font color="blue">TomcatB </h1>
<table align="centre" border="1">
<tr>
<td>Session ID</td>
<% session.setAttribute("abc","abc"); %>
<td><%= session.getId() %></td>
</tr>
<tr>
<td>Created on</td>
<td><%= session.getCreationTime() %></td>
</tr>
</table>
</body>
</html>
#检查配置文件并重新启动tomcat服务
[root@tomcat2 ~]# service tomcat stop
Using CATALINA_BASE: /usr/local/tomcat
Using CATALINA_HOME: /usr/local/tomcat
Using CATALINA_TMPDIR: /usr/local/tomcat/temp
Using JRE_HOME: /usr/local/jdk1.8.0_45
Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
[root@tomcat2 ~]# service tomcat configtest
Using CATALINA_BASE: /usr/local/tomcat
Using CATALINA_HOME: /usr/local/tomcat
Using CATALINA_TMPDIR: /usr/local/tomcat/temp
Using JRE_HOME: /usr/local/jdk1.8.0_45
Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
Jun 19, 2015 11:08:04 AM org.apache.catalina.core.StandardContext setPath
WARNING: A context path must either be an empty string or start with a '/' and do not end with a '/'. The path [/] does not meet these criteria and has been changed to []
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server version: Apache Tomcat/7.0.62
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server built: May 7 2015 17:14:55 UTC
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Server number: 7.0.62.0
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Name: Linux
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: OS Version: 2.6.32-358.el6.x86_64
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Architecture: amd64
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Java Home: /usr/local/jdk1.8.0_45/jre
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Version: 1.8.0_45-b14
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: JVM Vendor: Oracle Corporation
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_BASE: /usr/local/tomcat
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: CATALINA_HOME: /usr/local/tomcat
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.endorsed.dirs=/usr/local/tomcat/endorsed
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.base=/usr/local/tomcat
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Dcatalina.home=/usr/local/tomcat
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.VersionLoggerListener log
INFO: Command line argument: -Djava.io.tmpdir=/usr/local/tomcat/temp
Jun 19, 2015 11:08:04 AM org.apache.catalina.core.AprLifecycleListener lifecycleEvent
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
Jun 19, 2015 11:08:04 AM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["http-bio-80"]
Jun 19, 2015 11:08:04 AM org.apache.coyote.AbstractProtocol init
INFO: Initializing ProtocolHandler ["ajp-bio-8009"]
Jun 19, 2015 11:08:04 AM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1155 ms
#重新启动tomcat服务
[root@tomcat2 ~]# service tomcat start
Using CATALINA_BASE: /usr/local/tomcat
Using CATALINA_HOME: /usr/local/tomcat
Using CATALINA_TMPDIR: /usr/local/tomcat/temp
Using JRE_HOME: /usr/local/jdk1.8.0_45
Using CLASSPATH: /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
Tomcat started.
[root@tomcat2 ~]# netstat -tunlp |grep java
tcp 0 0 :::80 :::* LISTEN 1755/java
tcp 0 0 ::ffff:127.0.0.1:8005 :::* LISTEN 1755/java
tcp 0 0 :::8009 :::* LISTEN 1755/java
测试结果，将本地hosts解析调整到192.168.3.75 www.test.com上
6.安装apache
安装apr
[root@apache ~]# wget http://mirror.bit.edu.cn/apache//apr/apr-1.5.2.tar.gz [root@apache ~]# tar xf apr-1.5.2.tar.gz [root@apache ~]# cd apr-1.5.2 [root@apache apr-1.5.2]# ./configure --prefix=/usr/local/apr --disable-ipv6 [root@apache apr-1.5.2]# make && make install
安装apr-util
[root@apache ~]# wget http://mirror.bit.edu.cn/apache//apr/apr-util-1.5.4.tar.gz [root@apache ~]# tar xf apr-util-1.5.4.tar.gz [root@apache ~]# cd apr-util-1.5.4 [root@apache apr-util-1.5.4]# ./configure --prefix=/usr/local/apr-util --with-apr=/usr/local/apr/ [root@apache apr-util-1.5.4]# make && make install
安装apache
#解决依赖关系 [root@apache ~]# yum install pcre-devel openssl-devel -y #下载软件包 [root@apache ~]# wget http://mirrors.cnnic.cn/apache/httpd/httpd-2.4.12.tar.gz [root@apache ~]# tar xf httpd-2.4.12.tar.gz [root@apache ~]# cd httpd-2.4.12 #配置编译参数 [root@apache httpd-2.4.12]# ./configure \ > --prefix=/usr/local/apache \ > --sysconfdir=/etc/httpd \ > --enable-so \ > --enable-ssl \ > --enable-cgi \ > --enable-rewrite \ > --with-zlib \ > --with-pcre \ > --with-apr=/usr/local/apr \ > --with-apr-util=/usr/local/apr-util \ > --enable-mpms-shared=all \ > --with-mpm=event \ > --enable-proxy \ > --enable-proxy-http \ > --enable-proxy-ajp \ > --enable-proxy-balancer \ > --enable-lbmethod-heartbeat \ > --enable-heartbeat \ > --enable-slotmem-shm \ > --enable-slotmem-plain \ > --enable-watchdog [root@apache httpd-2.4.12]# make && make install
创建启动脚本
[root@apache ~]# cat /etc/init.d/httpd
#!/bin/bash
#
# httpd Startup script for the Apache HTTP Server
#
# chkconfig: - 85 15
# description: Apache is a World Wide Web server. It is used to serve \
# HTML files and CGI.
# processname: httpd
# config: /etc/httpd/conf/httpd.conf
# config: /etc/sysconfig/httpd
# pidfile: /var/run/httpd.pid
# Source function library.
. /etc/rc.d/init.d/functions
if [ -f /etc/sysconfig/httpd ]; then
. /etc/sysconfig/httpd
fi
# Start httpd in the C locale by default.
HTTPD_LANG=${HTTPD_LANG-"C"}
# This will prevent initlog from swallowing up a pass-phrase prompt if
# mod_ssl needs a pass-phrase from the user.
INITLOG_ARGS=""
# Set HTTPD=/usr/sbin/httpd.worker in /etc/sysconfig/httpd to use a server
# with the thread-based "worker" MPM; BE WARNED that some modules may not
# work correctly with a thread-based MPM; notably PHP will refuse to start.
# Path to the apachectl script, server binary, and short-form for messages.
apachectl=/usr/local/apache/bin/apachectl
httpd=${HTTPD-/usr/local/apache/bin/httpd}
prog=httpd
pidfile=${PIDFILE-/var/run/httpd.pid}
lockfile=${LOCKFILE-/var/lock/subsys/httpd}
RETVAL=0
start() {
echo -n $"Starting $prog: "
LANG=$HTTPD_LANG daemon --pidfile=${pidfile} $httpd $OPTIONS
RETVAL=$?
echo
[ $RETVAL = 0 ] && touch ${lockfile}
return $RETVAL
}
stop() {
echo -n $"Stopping $prog: "
killproc -p ${pidfile} -d 10 $httpd
RETVAL=$?
echo
[ $RETVAL = 0 ] && rm -f ${lockfile} ${pidfile}
}
reload() {
echo -n $"Reloading $prog: "
if ! LANG=$HTTPD_LANG $httpd $OPTIONS -t >&/dev/null; then
RETVAL=$?
echo $"not reloading due to configuration syntax error"
failure $"not reloading $httpd due to configuration syntax error"
else
killproc -p ${pidfile} $httpd -HUP
RETVAL=$?
fi
echo
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
status)
status -p ${pidfile} $httpd
RETVAL=$?
;;
restart)
stop
start
;;
condrestart)
if [ -f ${pidfile} ] ; then
stop
start
fi
;;
reload)
reload
;;
graceful|help|configtest|fullstatus)
$apachectl $@
RETVAL=$?
;;
*)
echo $"Usage: $prog {start|stop|restart|condrestart|reload|status|fullstatus|graceful|help|configtest}"
exit 1
esac
exit $RETVAL
#给脚本添加执行权限，并添加到开机自启动
[root@apache ~]# chmod +x /etc/init.d/httpd
[root@apache ~]# chkconfig --add httpd
[root@apache ~]# chkconfig httpd on
#启动httpd服务
[root@apache ~]# echo "ServerName localhost:80" >>/etc/httpd/httpd.conf
[root@apache ~]# service httpd start
Starting httpd: [ OK ]
[root@apache ~]# service iptables stop
三、负载均衡实现
两种方式都能实现负载均衡：
基于mod_proxy模块实现负载均衡
基于mod_jk模块实现负载均衡
下面我们就来分别演示一下，
1.基于mod_proxy实现负载均衡
首先我们来修改一下httpd.conf配置文件
[root@apache ~]# vim /etc/httpd/httpd.conf Include /etc/httpd/extra/httpd-proxy.conf #增加这一行
编辑httpd-proxy.conf文件
[root@apache ~]# cat /etc/httpd/extra/httpd-proxy.conf ProxyRequests Off <proxy balancer://lbcluster> BalancerMember ajp://192.168.3.74:8009 loadfactor=1 route=TomcatA BalancerMember ajp://192.168.3.75:8009 loadfactor=1 route=TomcatB ProxySet lbmethod=bytraffic </proxy> <VirtualHost *:80> ServerAdmin [email protected] ServerName www.test.com ProxyPass / balancer://lbcluster/ ProxyPassReverse / balancer://lbcluster/ stickysession=JSESSIONID <Proxy *> Require all granted </Proxy> <Location /> Require all granted </Location> </VirtualHost>
注，关于如上apache指令的说明：
ProxyPreserveHost {On|Off}：如果启用此功能，代理会将用户请求报文中的Host:行发送给后端的服务器，而不再使用ProxyPass指定的服务器地址。如果想在反向代理中支持虚拟主机，则需要开启此项，否则就无需打开此功能。
ProxyVia {On|Off|Full|Block}：用于控制在http首部是否使用Via:，主要用于在多级代理中控制代理请求的流向。默认为Off，即不启用此功能；On表示每个请求和响应报文均添加Via:；Full表示每个Via:行都会添加当前apache服务器的版本号信息；Block表示每个代理请求报文中的Via：都会被移除。
ProxyRequests {On|Off}：是否开启apache正向代理的功能；启用此项时为了代理http协议必须启用mod_proxy_http模块。同时，如果为apache设置了ProxyPass，则必须将ProxyRequests设置为Off。
ProxyPass [path] !|url [key=value key=value ...]]：将后端服务器某URL与当前服务器的某虚拟路径关联起来作为提供服务的路径，path为当前服务器上的某虚拟路径，url为后端服务器上某URL路径。使用此指令时必须将ProxyRequests的值设置为Off。需要注意的是，如果path以“/”结尾，则对应的url也必须以“/”结尾，反之亦然。
另外，mod_proxy模块在httpd 2.1的版本之后支持与后端服务器的连接池功能，连接在按需创建在可以保存至连接池中以备进一步使用。连接池大小或其它设定可以通过在ProxyPass中使用key=value的方式定义。常用的key如下所示：
min：连接池的最小容量，此值与实际连接个数无关，仅表示连接池最小要初始化的空间大小。
max：连接池的最大容量，每个MPM都有自己独立的容量；都值与MPM本身有关，如Prefork的总是为1，而其它的则取决于ThreadsPerChild指令的值。
loadfactor：用于负载均衡集群配置中，定义对应后端服务器的权重，取值范围为1-100。
retry：当apache将请求发送至后端服务器得到错误响应时等待多长时间以后再重试。单位是秒钟。
如果Proxy指定是以balancer://开头，即用于负载均衡集群时，其还可以接受一些特殊的参数，如下所示：
lbmethod：apache实现负载均衡的调度方法，默认是byrequests，即基于权重将统计请求个数进行调度，bytraffic则执行基于权重的流量计数调度，bybusyness通过考量每个后端服务器的当前负载进行调度。
maxattempts：放弃请求之前实现故障转移的次数，默认为1，其最大值不应该大于总的节点数。
nofailover：取值为On或Off，设置为On时表示后端服务器故障时，用户的session将损坏；因此，在后端服务器不支持session复制时可将其设置为On。
stickysession：调度器的sticky session的名字，根据web程序语言的不同，其值为JSESSIONID或PHPSESSIONID。
上述指令除了能在banlancer://或ProxyPass中设定之外，也可使用ProxySet指令直接进行设置，如：
<Proxy balancer://hotcluster> BalancerMember http://www1.test.com:8080 loadfactor=1 BalancerMember http://www2.test.com:8080 loadfactor=2 ProxySet lbmethod=bytraffic </Proxy>
ProxyPassReverse：用于让apache调整HTTP重定向响应报文中的Location、Content-Location及URI标签所对应的URL，在反向代理环境中必须使用此指令避免重定向报文绕过proxy服务器。
好了，配置文件说明就到这里。接下来我们检查一下配置文件并重启httpd
[root@apache ~]# /usr/local/apache/bin/httpd -t Syntax OK [root@apache ~]# service httpd restart Stopping httpd: [ OK ] Starting httpd: [ OK ]
访问结果
好了，大家可以看到基于mod_proxy模块的tomcat负载均衡配置完成。下面我们来配置一下基于mod_jk的模块的负载均衡！
2.基于mod_jk模块实现负载均衡
说明：
为了避免用户直接访问后端Tomcat实例，影响负载均衡的效果，建议在Tomcat 7的各实例上禁用HTTP/1.1连接器。
为每一个Tomcat 7实例的引擎添加jvmRoute参数，并通过其为当前引擎设置全局惟一标识符。如下所示。需要注意的是，每一个实例的jvmRoute的值均不能相同。
安装mod_jk
[root@apache ~]# wget http://mirrors.cnnic.cn/apache/tomcat/tomcat-connectors/jk/tomcat-connectors-1.2.40-src.tar.gz [root@apache ~]# tar xf tomcat-connectors-1.2.40-src.tar.gz [root@apache ~]# cd tomcat-connectors-1.2.40-src/native/ [root@apache native]# ./configure --with-apxs=/usr/local/apache/bin/apxs [root@apache native]# make && make install
同样的首先来修改httpd.conf配置文件
#禁用前面的httpd-proxy.conf文件，启用httpd-jk.conf文件 [root@apache ~]# vim /etc/httpd/httpd.conf #Include /etc/httpd/extra/httpd-proxy.conf Include /etc/httpd/extra/httpd-jk.conf #编辑httpd-jk.conf文件 [root@apache ~]# cat /etc/httpd/extra/httpd-jk.conf LoadModule jk_module modules/mod_jk.so #加载mod_jk模块 JkWorkersFile /etc/httpd/extra/workers.properties #配置文件位置 JkLogFile logs/mod_jk.log #日志 JkLogLevel debug #日志级别 JkMount /* lbcluster #负载均衡器名称 JkMount /jkstatus/ stat1 #状态信息
接下来，编辑/etc/httpd/extra/workers.properties，添加如下内容：
[root@apache ~]# cat /etc/httpd/extra/workers.properties worker.list = lbcluster,stat1 #列表信息 worker.TomcatA.type = ajp13 #支持ajp协议 worker.TomcatA.host = 192.168.3.74 #TomcatA实例IP worker.TomcatA.port = 8009 #TomcatA实例端口号 worker.TomcatA.lbfactor = 1 #负载均衡权重为1 worker.TomcatB.type = ajp13 worker.TomcatB.host = 192.168.3.75 worker.TomcatB.port = 8009 worker.TomcatB.lbfactor = 1 worker.lbcluster.type = lb #负载均衡work，lb内置的类 worker.lbcluster.sticky_session = 0 #会话是否绑定 worker.lbcluster.balance_workers = TomcatA, TomcatB #TomcatA, TomcatB 集群中的实列 worker.stat1.type = status #状态信息
注，apache相关指令说明：
workers.properties文件一般由两类指令组成：一是mod_jk可以连接的各worker名称列表，二是每一个worker的属性配置信息。它们分别遵循如下使用语法。
worker.list = < a comma separated list of worker names > worker. <worker name> .<property> = <property value>
其中worker.list指令可以重复指定多次，而worker name则是Tomcat中engine组件jvmRoute参数的值。如：
worker.TomcatA.host=172.16.100.1
根据其工作机制的不同，worker有多种不同的类型，这是需要为每个worker定义的一项属性woker.<work name>.type。常见的类型如下：
◇ ajp13：此类型表示当前worker为一个运行着的Tomcat实例。
◇ lb：lb即load balancing，专用于负载均衡场景中的woker；此worker并不真正负责处理用户请求，而是将用户请求调度给其它类型为ajp13的worker。
◇ status：用户显示分布式环境中各实际worker工作状态的特殊worker，它不处理任何请求，也不关联到任何实际工作的worker实例。具体示例如请参见后文中的配置。
worker其它常见的属性说明：
◇ host：Tomcat 7的worker实例所在的主机；
◇ port：Tomcat 7实例上AJP1.3连接器的端口；
◇ connection_pool_minsize：最少要保存在连接池中的连接的个数；默认为pool_size/2；
◇ connection_pool_timeout：连接池中连接的超时时长；
◇ mount：由当前worker提供的context路径，如果有多个则使用空格格开；此属性可以由JkMount指令替代；
◇ retries：错误发生时的重试次数；
◇ socket_timeout：mod_jk等待worker响应的时长，默认为0，即无限等待；
◇ socket_keepalive：是否启用keep alive的功能，1表示启用，0表示禁用；
◇ lbfactor：worker的权重，可以在负载均衡的应用场景中为worker定义此属性；
另外，在负载均衡模式中，专用的属性还有：
◇balance_workers：用于负载均衡模式中的各worker的名称列表，需要注意的是，出现在此处的worker名称一定不能在任何worker.list属性列表中定义过，并且worker.list属性中定义的worker名字必须包含负载均衡worker。具体示例请参见后文中的定义。
◇ method：可以设定为R、T或B；默认为R，即根据请求的个数进行调度；T表示根据已经发送给worker的实际流量大小进行调度；B表示根据实际负载情况进行调度。
◇sticky_session：在将某请求调度至某worker后，源于此址的所有后续请求都将直接调度至此worker，实现将用户session与某worker绑定。默认为值为1，即启用此功能。如果后端的各worker之间支持session复制，则可以将此属性值设为0。
下面我们来检查一下配置文件并重新启动一下httpd
[root@apache ~]# /usr/local/apache/bin/httpd -t Syntax OK [root@apache ~]# service httpd restart Stopping httpd: [ OK ] Starting httpd: [ OK ]
测试结果
