记录客户端操作我们一般使用cookie进行客户身份识别，session存储客户端的信息，session保存在服务器端。当我们负载均衡服务后，客户端请求定位到另外一台服务器，session信息在另外一台服务器上，为保证我们可以记录客户端进行的操作，我们一般有三种解决方式
第一种，session绑定，希望同一客户端的请求发往同一服务器，这样会破坏负载均衡效果。这种解决方法虽然有缺陷但是也是一种解决方法。
第二种，session cluster，构建一个session保存集群，提供同类型服务的服务器都把session共享，每个服务器一份。
第三种，session server，准备一个服务器保存session，然后其他服务器都到session服务器上取。
接下来，分布介绍他们怎么实现
环境准备
准备三台主机，他们之间的关系图如图1.1
图1.1
TomcatA的安装脚本
yum install tomcat tomcat-webapps tomcat-lib tomcat-admin-webapps
mkdir -pv /var/lib/tomcat/webapps/test/WEB-INF/{classes,lib}
cat > /var/lib/tomcat/webapps/test/index.jsp <<eof
<%@ page language="java" %>
<html>
<head><title>TomcatA</title></head>
<body>
<h1><font color="red">TomcatA.magedu.com</font></h1>
<table align="centre" border="1">
<tr>
<td>Session ID</td>
<% session.setAttribute("magedu.com","magedu.com"); %>
<td><%= session.getId() %></td>
</tr>
<tr>
<td>Created on</td>
<td><%= session.getCreationTime() %></td>
</tr>
</table>
</body>
</html>
eof还要配置Tomcat
vim /etc/tomcat/server.xml #在host配置段中添加如下一行 <Context path="/test" appBase="/var/lib/tomcat/webapps/test/" reloadable="true"/> #更改这一行 <Engine name="Catalina" defaultHost="localhost" jvmRoute="TomcatA">
TomcatB的安装脚本
yum install tomcat tomcat-webapps tomcat-lib tomcat-admin-webapps
mkdir -pv /var/lib/tomcat/webapps/test/WEB-INF/{classes,lib}
cat > /var/lib/tomcat/webapps/test/index.jsp <<eof
<%@ page language="java" %>
<html>
<head><title>TomcatB</title></head>
<body>
<h1><font color="blue">TomcatB.magedu.com</font></h1>
<table align="centre" border="1">
<tr>
<td>Session ID</td>
<% session.setAttribute("magedu.com","magedu.com"); %>
<td><%= session.getId() %></td>
</tr>
<tr>
<td>Created on</td>
<td><%= session.getCreationTime() %></td>
</tr>
</table>
</body>
</html>
eof还要配置Tomcat
vim /etc/tomcat/server.xml #在host配置段中添加如下一行 <Context path="/test" appBase="/var/lib/tomcat/webapps/test/" reloadable="true"/> #更改这一行 <Engine name="Catalina" defaultHost="localhost" jvmRoute="TomcatB">
session绑定的实现方法
session绑定的实现方法有三种，
第一种
使用Nginx的做反向代理，添加如下内容就可
vim /etc/nginx/nginx.conf
#在http配置段中添加一个
upstream tomcat {
server 172.16.29.10:8080;
server 172.16.29.20:8080;
ip_hash;
}
#在这个location调用upstream定义的负载均衡的两个服务器
location / {
proxy_pass http://tomcat;
}第二种
使用http的http反向代理模块，这里的会话绑定使用的是cookie
vim /etc/httpd/conf.d/tc.conf
Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e;path=/" env=BALANCER_ROUTE_CHANGED
<Proxy balancer://tomcat>
BalancerMember http://172.16.29.10:8080 route=TomcatA loadfactor=1
BalancerMember http://172.16.29.20:8080 route=TomcatB loadfactor=1
ProxySet lbmethod=byrequests
ProxySet stickysession=ROUTEID
</Proxy>
<VirtualHost *:80>
ServerName tc
ProxyRequests Off
ProxyVia On
ProxyPreserveHost On
<Proxy *>
Require all granted
</Proxy>
ProxyPass / balancer://tomcat:8080/
ProxyPassReverse / balancer://tomcat:8080/
<Location />
Require all granted
</Location>
</VirtualHost>第三种，使用http的ajp反向代理模块
vim /etc/httpd/conf.d/tc.conf
Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e;path=/" env=BALANCER_ROUTE_CHANGED
<Proxy balancer://tomcat>
BalancerMember ajp://172.16.29.10:8009 route=TomcatA loadfactor=1
BalancerMember ajp://172.16.29.20:8009 route=TomcatB loadfactor=1
ProxySet lbmethod=byrequests
ProxySet stickysession=ROUTEID
</Proxy>
<VirtualHost *:80>
ServerName tc
ProxyRequests Off
ProxyVia On
ProxyPreserveHost On
<Proxy *>
Require all granted
</Proxy>
ProxyPass / balancer://tomcat/
ProxyPassReverse / balancer://tomcat/
<Location />
Require all granted
</Location>
</VirtualHost>网页管理工具
vim /etc/httpd/conf.d/balancer.conf <Location /balancer-manager> SetHandler balancer-manager ProxyPass ! Require all granted </Location>
然后访问172.16.29.2/balancer-manager
session cluster的实现
实现session cluster使用的是，tomcat自带的cluster工具
在TomcatA的配置
vim /etc/tomcat/server.xml # 在Engine字段中添加如下内容 <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster" channelSendOptions="8"> <Manager className="org.apache.catalina.ha.session.DeltaManager" expireSessionsOnShutdown="false" notifyListenersOnReplication="true"/> <Channel className="org.apache.catalina.tribes.group.GroupChannel"> <Membership className="org.apache.catalina.tribes.membership.McastService" address="228.0.120.14" port="45564" frequency="500" dropTime="3000"/> <Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver" address="172.16.29.10" port="4000" autoBind="100" selectorTimeout="5000" maxThreads="6"/> <Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter"> <Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/> </Sender> <Interceptor className="org.apache.catalina.tribes.group.interceptors.TcpFailureDetector"/> <Interceptor className="org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor"/> </Channel> <Valve className="org.apache.catalina.ha.tcp.ReplicationValve" filter=""/> <Valve className="org.apache.catalina.ha.session.JvmRouteBinderValve"/> <Deployer className="org.apache.catalina.ha.deploy.FarmWarDeployer" tempDir="/tmp/war-temp/" deployDir="/tmp/war-deploy/" watchDir="/tmp/war-listen/" watchEnabled="false"/> <ClusterListener className="org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener"/> <ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener"/> </Cluster> vim /var/lib/tomcat/webapps/test/WEB-INF/web.xml # 在servlet字段前加如下内容 <distributable/> 在TomcatB的配置 vim /etc/tomcat/server.xml 在Engine字段中添加如下内容 <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster" channelSendOptions="8"> <Manager className="org.apache.catalina.ha.session.DeltaManager" expireSessionsOnShutdown="false" notifyListenersOnReplication="true"/> <Channel className="org.apache.catalina.tribes.group.GroupChannel"> <Membership className="org.apache.catalina.tribes.membership.McastService" address="228.0.120.14" port="45564" frequency="500" dropTime="3000"/> <Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver" address="172.16.29.20" port="4000" autoBind="100" selectorTimeout="5000" maxThreads="6"/> <Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter"> <Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/> </Sender> <Interceptor className="org.apache.catalina.tribes.group.interceptors.TcpFailureDetector"/> <Interceptor className="org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor"/> </Channel> <Valve className="org.apache.catalina.ha.tcp.ReplicationValve" filter=""/> <Valve className="org.apache.catalina.ha.session.JvmRouteBinderValve"/> <Deployer className="org.apache.catalina.ha.deploy.FarmWarDeployer" tempDir="/tmp/war-temp/" deployDir="/tmp/war-deploy/" watchDir="/tmp/war-listen/" watchEnabled="false"/> <ClusterListener className="org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener"/> <ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener"/> </Cluster>
vim /var/lib/tomcat/webapps/test/WEB-INF/web.xml # 在servlet字段前加如下内容 <distributable/>
session server的配置
这里的session server选择memcached,架构图如图1.2
图1.2
TomcatA和B的配置一样如下
vim /etc/tomcat/server.xml # 把原本的<Context>字段替换为如下的 <Context path="/test" appBase="/var/lib/tomcat/webapps/test/" reloadable="true"> <Manager className="de.javakaffee.web.msm.MemcachedBackupSessionManager" memcachedNodes="n1:172.16.29.30:11211,n2:172.16.29.40:11211" failoverNodes="n1" requestUriIgnorePattern=".*\.(ico|png|gif|jpg|css|js)$" transcoderFactoryClass="de.javakaffee.web.msm.serializer.javolution.JavolutionTranscoderFactory" /> </Context>
同时提供调用的模块，调用模块调用模块的地址如下http://down.51cto.com/data/2287135，这里的模块仅适用于Tomcat7
下载完导入/usr/share/java/tomcat/目录下就可以了
Tomcat8的把memcached-session-manager-tc7-1.8.3.jar替换为memcached-session-manager-tc8-1.8.3.jar就可以了，地址http://down.51cto.com/data/2287136
两个memcached配置
yum install memcached systemtcl start memcached
使用Nginx的做反向代理
vim /etc/nginx/nginx.conf
#在http配置段中添加一个
upstream tomcat {
server 172.16.29.10:8080;
server 172.16.29.20:8080;
}
#在这个location调用upstream定义的负载均衡的两个服务器
location / {
proxy_pass http://tomcat;
}本文出自 “老王linux旅程” 博客，请务必保留此出处http://oldking.blog.51cto.com/10402759/1896885
原文：http://oldking.blog.51cto.com/10402759/1896885